Sencha: the brewed drink and the dried leaf.

Sencha

Q: What is sencha?

Sencha is a Japanese green tea made from the leaves of the tea plant, Camellia sinensis. The fresh leaves are steamed, which keeps them green. Sencha, gyokuro and matcha are all Japanese green teas. The drink contains caffeine, the amino acid theanine and catechins.

Q: Is sencha the same as green tea extract?

No. A cup of tea is a weak water extract. Capsules and tablets are concentrated catechins and have been linked to rare serious liver injury. NCCIH reports no safety concerns for the drink in adults. Do not carry safety or benefit results from one to the other.

Q: Do Japanese people who drink green tea live longer?

In the Ohsaki study of 40,530 adults, heavier green tea drinkers had lower all-cause and cardiovascular death, and pooled data from eight Japanese cohorts showed a similar pattern. These are associations, drinkers may differ in other habits, and NCCIH says the heart link is seen in Asian but not Western groups. Neither study names sencha.

Q: Does it lower cholesterol or blood pressure?

Maybe slightly. A 2011 pooled analysis found small falls in total and LDL cholesterol, and a 2025 review of 36 trials found about 1 mmHg lower blood pressure, with big differences between trials. A 2020 review of short tea trials found no effect, and most trials mix drinks and extracts. Evidence is low.

Q: Does it help you lose weight?

Not much. A Cochrane review of 12 to 13 week trials found almost no weight change outside Japan (-0.04 kg on average). Japanese trials varied and could not be pooled.

Q: Does it prevent cancer?

This has not been shown. A Cochrane review of 142 studies found limited, inconsistent, low-certainty evidence, and the Ohsaki cohort found no lower cancer death in tea drinkers.

Q: Can it hurt the liver?

The drink rarely does. NCCIH reports no safety concerns for the beverage in adults, and liver injury is mostly linked to extract capsules and tablets. EFSA noted rare cases after infusions, likely an individual reaction. LiverTox lists liver failure and transplant for extracts. Stop any extract and get medical care if you notice yellow skin or eyes or dark urine.

Q: Is it safe in pregnancy, breastfeeding or for children?

Sencha has caffeine, so it counts toward your daily limit. The NHS says to have no more than 200 mg of caffeine a day in pregnancy and counts about 75 mg in a cup of black or green tea. LactMed reports infant fussiness only at extremely high maternal caffeine. Do not give tea to infants, and the FDA quotes guidance to avoid caffeinated drinks for children under 2. No source read covers extract capsules in pregnancy, so ask a clinician.

Q: Does it interact with medicines such as warfarin?

NCCIH says high doses of green tea lowered blood levels of nadolol and the extract lowered atorvastatin, and that a study showed an interaction with raloxifene. One 1999 case report links very large amounts of green tea with weaker warfarin effect. Ask your pharmacist or prescriber, and tell them about any big change in tea habits.

Camellia sinensis · also called Sencha, Japanese green tea, steamed green tea. Not the same as green tea extract capsules.

Sencha is a Japanese green tea made from tea plant leaves that are steamed soon after picking. People drink it for general wellbeing, focus and heart health. No study read names sencha itself, so the evidence comes from green tea in general: large Japanese surveys link heavy drinking with lower death rates, which does not prove tea is the cause. The drink has caffeine, and concentrated green tea extract capsules have been linked to rare serious liver injury.

General information, not medical advice. Last substantive update October 25, 2026 · Not medically reviewed. A named clinician has not signed off on this page. How this page is made

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About Sencha

Sencha is a Japanese steamed green tea. No study read separates it from other green tea. Large Japanese cohorts link heavy green tea drinking with lower death rates, and trials give small or uncertain results for cholesterol and blood pressure, almost nothing for weight or cancer, and no effect on blood sugar. NCCIH reports no safety concerns for the drink in adults beyond caffeine. Concentrated extract capsules are a separate product with rare serious liver injury reports and should not be judged by tea results.

Fluoride, aluminium and radioactivity testing

Tea plants take up fluoride and aluminium. A Slovenian study of 35 black and green teas found both in infusions and said drinking large quantities of high-fluoride, high-aluminium tea each day could potentially be a risk. A Polish study of 98 leaf teas found fluoride hazard values below the safety threshold, with the highest values in older, low-weight women drinking green tea. Neither study names Japanese tea types.

After the 2011 Fukushima accident, Japanese green tea has been tested for radioactive cesium. Health Canada's laboratory found trace amounts in Japanese green tea products, found that about 64% passed into the brewed drink, and estimated a dose far below natural radiation, with no health concern at those levels. Japan's national testing of more than 2.5 million food samples found 13 tea-based soft drink samples over the legal limit in 2012, and over 99% of monitored foods were low in recent years. Lead, cadmium, arsenic and pesticide figures for sencha were not found in the sources read.

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What it is

Sencha comes from the leaves of Camellia sinensis, a plant of the tea family (Theaceae) that GBIF accepts as a species. Green, black and oolong teas all come from this same plant. Japanese green tea, including sencha, gyokuro and matcha, is made by steaming freshly harvested leaves, which stops enzymes that would otherwise change the leaf.

A 2026 review says the amounts of catechins, caffeine and the amino acid theanine vary with harvest season, cultivar and growing, and in sencha also with water temperature and steeping time. Matcha is the whole leaf ground to powder, and extract capsules are concentrated catechins; each is a different product.

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Tea or extract?

A cup of sencha is a weak water extract of the leaf. A capsule or tablet packs catechins into a concentrated pill. The liver warnings and many trial results belong to the concentrated form. A systematic review of 159 human studies, written by authors at a supplement company, found liver events came from concentrated, catechin-rich preparations taken in large single doses, and not from brewed tea or extracts used in drinks or food. Do not carry results from one form to the other.

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What the research shows

The Ohsaki study followed 40,530 Japanese adults for up to 11 years and linked heavier green tea drinking with lower all-cause and cardiovascular death (strongest for stroke) but not with lower cancer death. A pooled analysis of eight Japanese cohorts found a similar pattern. These show a link and not a cause.

Cochrane found small falls in cholesterol and blood pressure from a few green tea trials, but the results were not stable and no trial reported heart attacks or strokes. A later review of 14 shorter tea trials found no effect on lipids or blood pressure. Outside Japan green tea gave almost no weight loss. Cancer results were inconsistent. For thinking, one review of mixed studies suggests a role for caffeine and L-theanine together. Trials of green tea supplements in type 2 diabetes found no effect on blood sugar.

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Regulators and status

The EMA has an EU herbal monograph and assessment report for green tea leaf; only the web page was read. EFSA judged traditional infusions generally safe at European intakes. NCCIH notes that the FDA approved a green tea extract ointment as a prescription drug for genital warts, which is a topical medicine and not a drink or supplement.

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At a glance

Traditional uses history, not proof

Japanese green tea is described as an essential beverage in Japanese culture, made with steaming of the fresh leaves (Kawahara 2024). The abstracts read give no dates for sencha.
Tea was first grown in China thousands of years ago, and NCCIH says tea has been used for health purposes for about 3,000 years.
Today green tea and its extracts are promoted as supplements for weight loss, lower cholesterol and prevention of chronic disease (NCCIH).

Studied for research

Death rates in Japanese drinkers (an association), low
Cholesterol, low
Blood pressure, low
Body weight, low
Staying independent in older age, low
Attention, flow and mood, very low to low
Stress relief (lab chemistry only), insufficient
Cancer risk, insufficient
Dementia and memory loss risk, very low
Blood sugar in type 2 diabetes, no effect found (against)

Main compounds

Catechins, mainly EGCG
Caffeine
L-theanine and other amino acids such as arginine
Tannins and other polyphenols

Common forms

Brewed tea from loose leaf or tea bags
Bottled and iced green tea
Matcha and gyokuro (other Japanese green teas, separate pages)
Concentrated green tea extract capsules and tablets (a different product with a liver warning)

Research links: NCCIH: Green Tea · Ohsaki cohort: green tea and mortality, JAMA 2006 (abstract) · EFSA opinion on green tea catechins (abstract) · Japanese green tea composition: matcha, sencha, gyokuro (abstract) · Cochrane: green tea and heart disease prevention (abstract) · Radiocesium in Japanese green tea, Health Canada study (abstract) · Research Library · Genes & Biomarkers Library

What it is and its history

Accepted scientific name: Camellia sinensis
Naming authority: (L.) Kuntze
Synonyms: Camellia bohea (L.) Sweet; Camellia chinensis (Sims) Kuntze; Camellia cantonensis Lour.
Common names: Sencha (Japanese); Japanese green tea (English); Steamed green tea (English)
Family or group: Theaceae (the tea family)
Classification: Plantae > Ericales > Theaceae > Camellia > Camellia sinensis
Native range: Not checked in the sources read (NCCIH says tea was first cultivated in China thousands of years ago).
Habitat: Not checked.
What it looks like: Stems: Stems are present in some tea products (LactMed).; Leaves: The leaf is the part used; for Japanese green tea the fresh leaf is steamed, then rolled and dried (steaming per Kawahara 2024; other steps not described in the sources read).; Flowers: Not checked.; Fruit: Not checked.
Cultivation: Not checked.
Harvest and processing: Japanese green tea is characterised by steaming the freshly harvested leaves, which inactivates enzymes such as polyphenol oxidases and keeps the green colour (Kawahara 2024). Sencha composition varies with harvest timing, cultivar, water temperature and steeping time (Unno 2026).
Look-alikes and adulterants: Name: Matcha, gyokuro and other teas; Note: Matcha and gyokuro are also Japanese green teas; black and oolong come from the same plant but are fermented. Green tea extract capsules are a concentrated product and behave differently from brewed tea.
Sustainability and conservation: Not checked.

Photographs

A clear glass cup of pale yellow-green sencha beside a small pile of dried sencha leaves — Sencha: the brewed drink and the dried leaf.

Traditional use and history history, not clinical proof

Tradition or era	Documented use	Source
China, early use	NCCIH says tea was first cultivated in China thousands of years ago and that tea was used for health purposes for about 3,000 years.	s-nccih-green-tea
European herbal medicine	EMA has an EU herbal monograph and assessment report for green tea leaf (Camelliae sinensis non fermentatum folium) with therapeutic area "Fatigue and weakness". The wording of the monograph was not read.	s-ema-hmpc-green-tea
Today	NCCIH says green tea and extracts are promoted as supplements for weight loss, lower cholesterol and prevention of chronic disease, and that the FDA approved a topical green tea extract ointment for genital warts.	s-nccih-green-tea
Japan	A 2024 plant-genetics paper describes Japanese green tea as 'an essential beverage in Japanese culture' made with initial steaming of fresh leaves. The abstracts read give no dates or earlier history for sencha.	p38807462

Traditional use shows how it was used. It does not show that it works or is safe today.

What is inside, and how it may work

What it contains and how those compounds act in cells and animals. Laboratory and animal mechanisms are not proven effects in people.

Main compounds

Compound	Family	Where it is concentrated	Activity studied	Level of evidence
Epigallocatechin gallate (EGCG) PubChem 65064	catechin (polyphenol)	Leaf The main catechin in green tea (EFSA). Amounts in sencha vary with harvest time, cultivar and steeping conditions (Unno 2026).	Liver effects at high supplement doses; other actions not established in the sources read. ^{38 5 31}	Human data
Caffeine PubChem 2519	purine alkaloid	Leaf 37 mg per 12 fl oz drink (FDA).	Stimulant; see Safety tab. ^{39 34}	Human data
L-theanine PubChem 439378	amino acid	Leaf Varies by tea; authors note Japanese green teas such as gyokuro and matcha are high in theanine and that amounts depend on harvest, cultivar and growing (Unno 2026).	Reviewers link benefits for attention to caffeine and L-theanine together. ^{40 19 21 31}	Human data
Tannins and other polyphenols	polyphenols	Leaf and stem Not given.	Tea polyphenols lower iron absorption (radio-iron study, black and herb teas). ^{21 10}	Human data
Arginine	amino acid	Leaf Measured in Japanese green teas in 2022; not quoted here.	Authors propose theanine and arginine counter the stimulating effects of caffeine and EGCG (lab indicator only). ³⁰	Lab

Mechanisms, receptors and pathways

Target or pathway	Gene or receptor	What was found	Level
Energy use (hypothesis)	n/a	The Cochrane weight review states that catechins and caffeine are believed to increase energy metabolism; it found almost no weight change outside Japan. ¹³	Hypothesis by reviewers
Liver injury from concentrated EGCG	UGT1A4 and COMT variants (secondary trial analysis); an immune-related gene variant (NCCIH)	Toxicology review: liver is the target organ in lab studies, tied to large single doses and fasting and to EGCG content. In a secondary trial analysis, women with the UGT1A4 A/C variant had larger ALT rises on high-dose extract. ^{9 2 35}	Lab and human
Caffeine plus L-theanine on attention	n/a	Cognitive benefits were seen with caffeine and L-theanine together and less with either alone. ¹⁹	Human review
Iron absorption	n/a	Tea polyphenols reduce absorption of non-haem iron in a dose-related way (radio-iron study of black and herb teas). ¹⁰	Human data
Caffeine and EGCG versus theanine and arginine (proposed indicator)	n/a	Authors propose a ratio of caffeine plus EGCG to theanine plus arginine; sencha, gyokuro and tamaryokucha were below 3 in a lab analysis. No people were tested. ^{30 31}	Lab indicator

Absorption, metabolism and elimination

Absorption: Not covered in the sources read.
Distribution: Not covered.
Metabolism: A secondary trial analysis links the enzymes COMT and UGT1A4 with liver enzyme changes on high-dose extract.
Elimination: Not covered.
Bioavailability: Not covered.

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Isolated compounds versus whole extracts

Brewed tea, powdered whole leaf (matcha), liquid extracts and concentrated EGCG capsules are different products. EFSA estimates that supplements can deliver far more EGCG than infusions do; liver warnings come from the concentrated form. Hu and colleagues found liver events from concentrated preparations in large single doses, not from brewed tea. Trial results for extract cannot be applied to the drink, or the other way round.

Nutritional composition

Green tea is not a source of essential nutrients in the sources read. It contains caffeine, L-theanine, catechins and tannins.

11benefits and uses looked at

41studies and sources checked

Low certaintybest evidence rating found

6lab markers tracked in trials

6 low certainty2 very low certainty2 not enough evidence1 evidence against

What was looked at

The 11 benefits and uses checked for Sencha, each with how strong the evidence is. Tap one to open it.

CholesterolLow certainty
Blood pressureLow certainty
Body weightLow certainty
Cancer riskNot enough evidence
Heart disease and death rates in drinkersLow certainty
Attention, memory and moodLow certainty
Flow and steady alertness during mental tasksVery low certainty
Stress relief (lab chemistry only)Not enough evidence
Dementia and memory loss riskVery low certainty
Staying independent in older age (functional disability)Low certainty
Blood sugar in type 2 diabetesEvidence against

Lab markers tracked in the studies

LDL cholesterolSystolic blood pressureBody weightDeath from any causeHbA1cAttention and memory tests

What is Sencha good for?

The uses people ask about and how strong the human evidence is for each. No study read names sencha, and most trials mix the drink with extracts, so none of these results is a clean answer about a cup of sencha.

Heart disease and death rates in Japanese drinkersLow certaintyIn the Ohsaki study of 40,530 Japanese adults, people who drank 5 or more cups of green tea a day had lower all-cause death than those who drank under 1 (men HR 0.88, women HR 0.77), with the strongest link for stroke. In eight pooled Japanese cohorts the lowest death rates were also in heavy drinkers. This is an association only. CholesterolLow certaintyPooled trials of green tea drinks and extracts found small falls in total and LDL cholesterol, but a later review of shorter tea trials found no effect. NCCIH says most trials tested extracts. Blood pressureLow certaintyA 2025 review of 36 trials found average falls of about 1 mmHg with big differences between trials. A review of short tea trials found no effect. Body weightLow certaintyA Cochrane review found almost no weight change outside Japan (average -0.04 kg). Japanese trials varied and could not be pooled. Staying independent in older ageLow certaintyAmong 13,988 Japanese adults aged 65 or older, those drinking 5 or more cups a day were less likely to need care support over three years (HR 0.67). An association from one cohort. Attention, memory and moodLow certaintyA review of 21 mostly small studies reported better attention and memory and less anxiety, with caffeine and L-theanine working together. It mixes drinks, extracts and isolated compounds. Flow and steady alertness during a taskVery low certaintyIn 22 young men, sips of green tea kept alertness up and raised a flow score but did not change task accuracy. It was a very small study with tea company authors. Stress relief (lab chemistry only)Not enough evidenceA lab analysis found sencha has an ingredient mix the authors expect to go with calming effects. No people were tested, so this is not evidence that sencha relieves stress. Cancer riskNot enough evidenceA Cochrane review of 142 studies found limited, inconsistent, low-certainty results. In the Ohsaki cohort cancer deaths were not lower in tea drinkers. It does not show that green tea prevents cancer. Dementia and memory loss riskVery low certaintyEight observational studies gave mixed results. A Japanese study of 1,003 older adults found less cognitive impairment in people drinking 2 or more cups a day, but it looked at one point in time and cannot show cause. Blood sugar in type 2 diabetesEvidence againstA meta-analysis of 14 trials found no significant effect of green tea supplements on blood sugar measures.

Benefits, one by one

Each card is a research question, not a promise. Tap a goal to filter. Open a card to see the studies, doses and limits.

Cholesterol

Low certainty

Pooled trials of green tea drinks and extracts show a small average fall in total and LDL cholesterol. Two reviews disagree, and most of the trial data comes from extract or mixed products, so the result for a cup of tea is uncertain.

4 studiesMixed: drinks and extracts. Not a drink-only result.

Studies, doses and limits

What the trials found

A 2011 meta-analysis of 14 trials (1,136 people) of green tea drinks or extracts found a small fall in total and LDL cholesterol and no change in HDL. A Cochrane review of 7 green tea trials found larger falls that were not stable when checked. A 2020 review of 14 shorter trials of green or black tea (4 to 24 weeks) found no significant effect. NCCIH says most trials tested extract supplements, not the drink.

Results

Total cholesterol -7.20 mg/dL (95% CI -8.19 to -6.21) and LDL -2.19 mg/dL (-3.16 to -1.21) in the 2011 pooled trials; Cochrane green tea: total -0.62 mmol/L and LDL -0.64 mmol/L, not stable to sensitivity analysis; 2020 review: no significant change.

Effect sizes as reported

Small average falls; reviewers disagree on whether they are real in short trials.

Why this rating

Pooled drinks and extracts, small trials, results not stable, a later review found no effect.

Form and dose studied

Mixed: drinks and extracts. Not a drink-only result.

Who was studied

Healthy adults and adults at higher risk, mostly short trials.

Limits

Product types differ; most trials are short; no heart attack or stroke outcomes. No study here names sencha; the results are for green tea in general.

Why researchers looked

High LDL cholesterol is a risk factor for heart disease, and green tea catechins are often said to help.

Traditional use

Not described in the sources read.

Proposed mechanism Not established

No mechanism was established in the sources read.

A proposed mechanism does not show that the effect happens in people.

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Blood pressure

Low certainty

Reviews find a very small average fall in blood pressure, with big differences between studies. One review of short trials found no effect.

3 studiesGreen tea supplementation; the 2025 abstract does not separate drink …

Studies, doses and limits

What the trials found

A 2025 meta-analysis of 36 trials of green tea supplementation found average falls of about 1 mmHg in both systolic and diastolic pressure with very high differences between trials. The Cochrane review found larger falls (about 3 mmHg) from a small number of green tea trials that were not stable. A 2020 review of 14 trials of green or black tea (4 to 24 weeks) found no significant effect.

Results

Systolic -1.08 mmHg (95% CI -1.98 to -0.18), diastolic -1.09 mmHg (-1.67 to -0.50) in 36 trials; Cochrane green tea systolic -3.18 mmHg, diastolic -3.42 mmHg, unstable; 2020 review: no significant effect.

Effect sizes as reported

About 1 to 3 mmHg at most.

Why this rating

Very large differences between trials (I2 74 to 85 percent), unstable Cochrane result, one review with no effect.

Form and dose studied

Green tea supplementation; the 2025 abstract does not separate drink from extract.

Who was studied

Adults, with stronger effects in people who started with raised blood pressure.

Limits

Heterogeneity; mixed forms; small average change that may not matter to health. No study here names sencha; the results are for green tea in general.

Why researchers looked

High blood pressure is a leading risk factor for heart disease and stroke.

Traditional use

Not described in the sources read.

Proposed mechanism Not established

No mechanism was established in the sources read.

A proposed mechanism does not show that the effect happens in people.

Brewed green tea has no safety concerns reported in adults (NCCIH) but contains caffeine. Concentrated extract capsules are a different product with rare serious liver injury reports. See the Safety tab. The authors call green tea a complementary approach, not a treatment for high blood pressure.

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Body weight

Low certainty

A Cochrane review found almost no weight loss from green tea outside Japan. The Japanese trials were too different to combine and ranged from little change to a few kilograms.

2 studiesGreen tea preparations, drinks and extracts.

Studies, doses and limits

What the trials found

The review included trials of at least 12 weeks in overweight or obese adults: six outside Japan (532 people) and eight in Japan (1,030 people).

Results

Outside Japan: weight -0.04 kg (95% CI -0.5 to 0.4), BMI -0.2 kg/m2, waist -0.2 cm; none significant. Japanese trials ranged from -0.2 to -3.5 kg and could not be pooled.

Effect sizes as reported

No meaningful change outside Japan.

Why this rating

Short trials of 12 to 13 weeks, many preparation types, results differ by region.

Form and dose studied

Green tea preparations, drinks and extracts.

Who was studied

Overweight and obese adults.

Limits

Not a drink-only result; short. No study here names sencha; the results are for green tea in general.

Why researchers looked

Green tea contains catechins and caffeine, which reviewers say are believed to raise energy use.

Traditional use

NCCIH says green tea and extracts are promoted for weight loss.

Proposed mechanism Hypothesis

The Cochrane reviewers state a belief that catechins and caffeine may raise energy metabolism; they say the efficacy remains unclear.

A proposed mechanism does not show that the effect happens in people.

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Cancer risk

Not enough evidence

A large Cochrane review found inconsistent, low-certainty results. It does not show that green tea prevents cancer.

3 studiesExtract in trials; drinking in observational studies.

Studies, doses and limits

What the trials found

The review used 142 studies: 11 trials of green tea extract (1,795 people) and 131 observational studies (over 1,100,000 people).

Results

Extract trials: prostate cancer RR 0.50 (95% CI 0.18 to 1.36), gynaecological RR 1.50 (0.41 to 5.48), skin RR 1.00 (0.06 to 15.92). Observational highest versus lowest intake: cancer incidence RR 0.83 (0.65 to 1.07); cancer death RR 0.99 (0.91 to 1.07). Results conflicted between study designs for some cancers. In the large Ohsaki cohort, cancer death was not lower in green tea drinkers (hazard ratios not different from 1.00).

Effect sizes as reported

Intervals include no effect.

Why this rating

Low-certainty and inconsistent results; mostly observational; Asian populations.

Form and dose studied

Extract in trials; drinking in observational studies.

Who was studied

Adults, mostly in Asia.

Limits

Cannot show cause; trials used extract. No study here names sencha; the results are for green tea in general.

Why researchers looked

Lab studies have suggested catechins may slow cancer cell growth; population studies have asked whether tea drinkers get less cancer.

Traditional use

Not described in the sources read.

Proposed mechanism Lab only

Cochrane notes that laboratory studies have suggested catechins may inhibit cancer cell growth. This is lab work and not shown in people.

A proposed mechanism does not show that the effect happens in people.

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Heart disease and death rates in drinkers

Low certainty

In Japan, people who drank five or more cups a day had somewhat lower death rates than people who drank less than one. This is an association and does not show tea caused it.

3 studiesGreen tea as a drink.

Studies, doses and limits

What the trials found

A pooled analysis of eight Japanese cohorts followed 313,381 people for a mean 17.3 years. The earlier Ohsaki cohort followed 40,530 adults in one Japanese region for up to 11 years.

Results

Five or more cups a day versus less than one: all-cause death HR 0.90 (0.87 to 0.94) in men and 0.82 (0.74 to 0.90) in women; heart disease HR 0.82 and 0.75; stroke-type HR 0.76 and 0.78. In women only, total cancer death HR 0.89 (0.83 to 0.96) at 1 to 2 cups. In the Ohsaki cohort (JAMA 2006), 5 or more cups a day versus under 1 gave all-cause death HR 0.88 (0.79 to 0.98) in men and 0.77 (0.67 to 0.89) in women, with the strongest link for stroke death and no link with cancer death.

Effect sizes as reported

Roughly 10 to 18 percent lower all-cause death among the heaviest drinkers.

Why this rating

Observational; healthier lifestyle among drinkers cannot be ruled out; Japanese data; sencha not named.

Form and dose studied

Green tea as a drink.

Who was studied

Japanese adults.

Limits

Self-reported intake; cannot show cause; may not apply outside Japan. No study here names sencha; the results are for green tea in general.

Why researchers looked

Green tea is part of daily life in Japan, so large cohorts can compare heavy and light drinkers.

Traditional use

NCCIH notes that lower heart disease risk has been linked to green tea in Asian but not Western groups.

Proposed mechanism Not established

Not established. Observational data cannot identify a mechanism.

A proposed mechanism does not show that the effect happens in people.

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Attention, memory and mood

Low certainty

A systematic review found signs of better attention and memory and less anxiety, mostly in small or short studies. The effect seems to come from caffeine and L-theanine together.

1 studiesGreen tea, green tea extract, L-theanine and EGCG.

Studies, doses and limits

What the trials found

Mancini 2017 reviewed 21 studies (4 randomised trials, 12 crossover studies, 4 cross-sectional studies, 1 cohort) on green tea, green tea extract, L-theanine and EGCG.

Results

The reviewers report evidence of less anxiety, better memory and attention and brain-scan changes with working memory. The abstract gives no numbers.

Effect sizes as reported

Not given in the abstract.

Why this rating

Mixed products (drink, extract, isolated L-theanine), many short or single-dose studies, no numbers in abstract.

Form and dose studied

Green tea, green tea extract, L-theanine and EGCG.

Who was studied

Mostly healthy adults.

Limits

Not a drink-only result; PubMed only; reviewers own quality scores. No study here names sencha; the results are for green tea in general.

Why researchers looked

Green tea contains caffeine and L-theanine, and people drink it for alertness with calm.

Traditional use

Not described in the sources read.

Proposed mechanism Human study observation

The reviewers say the effect cannot be put down to one ingredient: benefits for cognition appeared with caffeine and L-theanine together and were smaller with either alone.

A proposed mechanism does not show that the effect happens in people.

¹⁹

Flow and steady alertness during mental tasks

Very low certainty

One very small Japanese study of 22 young men found that sipping green tea kept alertness up and gave a higher flow score, but did not change accuracy. A tea company took part in the study.

1 studiesGreen tea drink in small sips (210 mL in total).

Studies, doses and limits

What the trials found

Crossover study in 22 healthy young Japanese men (Kurosaka 2025): green tea versus water versus no drink.

Results

Task accuracy did not differ (it was above 95% in all conditions). With tea, arousal was maintained and mental fatigue did not rise, and the flow score was higher than with no drink (p=0.0009).

Effect sizes as reported

Not given in the abstract.

Why this rating

22 young men, one short session, mostly self-rated; the tea type is not named in the abstract; authors from a tea company (ITOEN) and one consultant honorarium from the funder.

Form and dose studied

Green tea drink in small sips (210 mL in total).

Who was studied

Healthy young Japanese men.

Limits

Industry-linked; very small; accuracy could not differ because it was near perfect. The tea is not named; the results are for green tea in general.

Why researchers looked

Green tea has caffeine and the amino acid theanine, and people drink it to feel alert and calm.

Traditional use

Not described in the sources read.

Proposed mechanism Hypothesis by authors

Not tested. The authors suggest low-dose habitual green tea may help task engagement.

A proposed mechanism does not show that the effect happens in people.

Contains caffeine. See the Safety tab.

¹⁸

Stress relief (lab chemistry only)

Not enough evidence

A lab analysis of Japanese green teas, including sencha, found a mix of ingredients that the authors expect to go with calming effects. No people were tested, so this is not evidence that sencha relieves stress.

2 studiesSencha leaves and infusions (lab).

Studies, doses and limits

Results

Most amino acids came out in the first and second infusions, so the authors expected no such effect from the third cup onward. A 2026 narrative review says sencha composition varies with harvest season, cultivar, water temperature and steeping time.

Why this rating

Lab indicator only; no person was tested in these papers.

Form and dose studied

Sencha leaves and infusions (lab).

Limits

A proposed indicator, not a trial.

Why researchers looked

Sencha has theanine and arginine, which the authors link with calm, and caffeine and EGCG, which they say work against it.

Traditional use

Not described in the sources read.

Proposed mechanism Lab indicator

The authors propose a ratio of caffeine plus EGCG to theanine plus arginine. A ratio below 3 is expected to go with a stress-relieving effect. Sencha, gyokuro and tamaryokucha were below 3.

A proposed mechanism does not show that the effect happens in people.

Contains caffeine. See the Safety tab.

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Dementia and memory loss risk

Very low certainty

Observational studies lean towards lower risk in green tea drinkers, but they are few and mixed, and cannot show that tea is the reason.

2 studiesGreen tea as a drink.

Studies, doses and limits

What the trials found

A 2019 systematic review found 3 cohort and 5 cross-sectional studies. A separate Japanese cross-sectional study (Tsurugaya Project) looked at 1,003 adults aged 70 or older.

Results

One cohort and three cross-sectional studies supported a benefit, one cohort and one cross-sectional study partly supported it, and one of each found no link. In that Japanese study, drinking 2 or more cups of green tea a day went with lower odds of cognitive impairment (OR 0.46, 95% CI 0.30 to 0.72); black or oolong tea and coffee did not show a clear link. A cross-sectional study cannot show which came first.

Effect sizes as reported

Not given in the abstract.

Why this rating

Eight observational studies, mixed results, cannot show cause.

Form and dose studied

Green tea as a drink.

Who was studied

Mostly Asian adults.

Limits

Observational; small number of studies. No study here names sencha; the results are for green tea in general.

Why researchers looked

Population studies in Asia asked whether regular green tea drinkers keep their memory longer.

Traditional use

Not described in the sources read.

Proposed mechanism Not established

Not established.

A proposed mechanism does not show that the effect happens in people.

^{14 17}

Staying independent in older age (functional disability)

Low certainty

In a large Japanese cohort of people aged 65 or older, those who drank more green tea were less likely to need care support over the next three years. This is an association only.

1 studiesGreen tea as a drink (type not named).

Studies, doses and limits

What the trials found

Ohsaki Cohort 2006: 13,988 Japanese adults aged 65 or older followed for 3 years (Tomata 2012).

Results

Compared with under 1 cup a day, the hazard of later functional disability was 0.90 (0.77 to 1.06) at 1 to 2 cups, 0.75 (0.64 to 0.88) at 3 to 4 cups and 0.67 (0.57 to 0.79) at 5 or more cups a day.

Effect sizes as reported

About one third lower hazard at the highest intake group, after adjustment.

Why this rating

One observational cohort in Japan; short follow-up; self-reported tea intake; healthier people may drink more tea.

Form and dose studied

Green tea as a drink (type not named).

Who was studied

Japanese adults aged 65 or older.

Limits

Cannot show cause; sencha not named; may not apply outside Japan.

Why researchers looked

Green tea is a daily habit in Japan, and researchers asked whether it goes with healthier ageing.

Traditional use

Not described in the sources read.

Proposed mechanism Not established

Not established. The authors point to links with stroke, cognitive impairment and bone loss, which this observational study did not test.

A proposed mechanism does not show that the effect happens in people.

Brewed green tea has no safety concerns reported in adults (NCCIH) but contains caffeine. See the Safety tab.

²⁹

Blood sugar in type 2 diabetes

Evidence against

A meta-analysis of 14 trials found no significant effect of green tea supplements on blood sugar measures in people with type 2 diabetes.

1 studiesGreen tea supplementation; type not stated in the abstract.

Studies, doses and limits

What the trials found

A 2021 meta-analysis pooled 14 randomised trials in people with type 2 diabetes.

Results

No significant effect on fasting glucose, fasting insulin, HbA1c or insulin resistance (HOMA-IR).

Effect sizes as reported

No significant effect.

Why this rating

One meta-analysis of 14 trials found no effect; the abstract does not give the product type; small trials, so no effect is not proof of none.

Form and dose studied

Green tea supplementation; type not stated in the abstract.

Who was studied

Adults with type 2 diabetes.

Limits

Small trials; form unclear. No study here names sencha; the results are for green tea in general.

Why researchers looked

Catechins have been proposed to affect blood sugar and insulin.

Traditional use

Not described in the sources read.

Proposed mechanism Not established

Not established in the source read.

A proposed mechanism does not show that the effect happens in people.

Brewed green tea has no safety concerns reported in adults (NCCIH) but contains caffeine. Concentrated extract capsules are a different product with rare serious liver injury reports. See the Safety tab. People taking diabetes medicines should speak to their prescriber before using any supplement.

Connections to the rest of health

How Sencha connects to the rest of our health knowledge graph. Every link says what kind of connection it is. A safety link (for example to the liver) is a warning, not a benefit. A study that merely mentions a topic never creates a benefit link.

Explore every connection: goals, body systems, organs, symptoms, genes

Kind of connection Connected to Search

A. Wellness goals

Connected to	Kind of connection	Evidence status	Context	Studies
Cholesterol Balance		Low certainty	Cholesterol: Pooled trials of green tea drinks and extracts show a small average fall in total and LDL cholesterol. Two reviews disagree, and most of the trial data comes from extract or mixed products, so the result for a cup of tea is uncertain.	^{32 7 11 35}
Heart Health		Low certainty	Cholesterol: Pooled trials of green tea drinks and extracts show a small average fall in total and LDL cholesterol. Two reviews disagree, and most of the trial data comes from extract or mixed products, so the result for a cup of tea is uncertain. Blood pressure: Reviews find a very small average fall in blood pressure, with big differences between studies. One review of short trials found no effect.	^{32 7 11 35 26}
Blood Pressure Support		Low certainty	Blood pressure: Reviews find a very small average fall in blood pressure, with big differences between studies. One review of short trials found no effect.	^{26 7 11}
Weight Management		Low certainty	Body weight: A Cochrane review found almost no weight loss from green tea outside Japan. The Japanese trials were too different to combine and ranged from little change to a few kilograms.	^{13 35}
Preventive Wellness		Not enough evidence	Cancer risk: A large Cochrane review found inconsistent, low-certainty results. It does not show that green tea prevents cancer.	^{6 35 16}
Heart Health	Biological association	Low certainty	Heart disease and death rates in drinkers: In Japan, people who drank five or more cups a day had somewhat lower death rates than people who drank less than one. This is an association and does not show tea caused it.	^{1 16 35}
Longevity	Biological association	Low certainty	Heart disease and death rates in drinkers: In Japan, people who drank five or more cups a day had somewhat lower death rates than people who drank less than one. This is an association and does not show tea caused it.	^{1 16 35}
Mental Clarity		Low certainty	Attention, memory and mood: A systematic review found signs of better attention and memory and less anxiety, mostly in small or short studies. The effect seems to come from caffeine and L-theanine together. Flow and steady alertness during mental tasks: One very small Japanese study of 22 young men found that sipping green tea kept alertness up and gave a higher flow score, but did not change accuracy. A tea company took part in the study.	^{19 18}
Better Focus		Low certainty	Attention, memory and mood: A systematic review found signs of better attention and memory and less anxiety, mostly in small or short studies. The effect seems to come from caffeine and L-theanine together. Flow and steady alertness during mental tasks: One very small Japanese study of 22 young men found that sipping green tea kept alertness up and gave a higher flow score, but did not change accuracy. A tea company took part in the study.	^{19 18}
Memory Support		Low certainty	Attention, memory and mood: A systematic review found signs of better attention and memory and less anxiety, mostly in small or short studies. The effect seems to come from caffeine and L-theanine together.	¹⁹
Brain Health		Low certainty	Attention, memory and mood: A systematic review found signs of better attention and memory and less anxiety, mostly in small or short studies. The effect seems to come from caffeine and L-theanine together.	¹⁹
Stress Reduction		Not enough evidence	Stress relief (lab chemistry only): A lab analysis of Japanese green teas, including sencha, found a mix of ingredients that the authors expect to go with calming effects. No people were tested, so this is not evidence that sencha relieves stress.	^{30 31}
Calm Relaxation		Not enough evidence	Stress relief (lab chemistry only): A lab analysis of Japanese green teas, including sencha, found a mix of ingredients that the authors expect to go with calming effects. No people were tested, so this is not evidence that sencha relieves stress.	^{30 31}
Brain Health	Biological association	Very low certainty	Dementia and memory loss risk: Observational studies lean towards lower risk in green tea drinkers, but they are few and mixed, and cannot show that tea is the reason.	^{14 17}
Healthy Aging	Biological association	Very low certainty	Dementia and memory loss risk: Observational studies lean towards lower risk in green tea drinkers, but they are few and mixed, and cannot show that tea is the reason. Staying independent in older age (functional disability): In a large Japanese cohort of people aged 65 or older, those who drank more green tea were less likely to need care support over the next three years. This is an association only.	^{14 17 29}
Mobility Support	Biological association	Low certainty	Staying independent in older age (functional disability): In a large Japanese cohort of people aged 65 or older, those who drank more green tea were less likely to need care support over the next three years. This is an association only.	²⁹
Blood Sugar Balance		Evidence against	Blood sugar in type 2 diabetes: A meta-analysis of 14 trials found no significant effect of green tea supplements on blood sugar measures in people with type 2 diabetes.	³
Metabolic Health		Evidence against	Blood sugar in type 2 diabetes: A meta-analysis of 14 trials found no significant effect of green tea supplements on blood sugar measures in people with type 2 diabetes.	³

B. Body systems

Connected to	Kind of connection	Evidence status	Context	Studies
Cardiovascular System	Biological association	Low certainty	Studied for: Cholesterol Studied for: Blood pressure	^{32 7 11 35 26 1 16}
Metabolism Weight	Biological association	Low certainty	Studied for: Body weight Studied for: Blood sugar in type 2 diabetes	^{13 35 3}
Cellular	Biological association	Not enough evidence	Studied for: Cancer risk	^{6 35 16}
Brain Focus	Biological association	Low certainty	Studied for: Attention, memory and mood Studied for: Flow and steady alertness during mental tasks	^{19 18 14 17 29}
Stress Mood	Biological association	Not enough evidence	Studied for: Stress relief (lab chemistry only)	^{30 31}

C. Body parts and organs

Connected to	Kind of connection	Evidence status	Context	Studies
Liver	Adverse effect or risk	Low certainty	Rare liver injury, mostly with extract; case reports and trials of high-dose EGCG. Preparation or compound: Concentrated green tea extract; rarely tea	^{22 5 25}

E. Health conditions

Connected to	Kind of connection	Evidence status	Context	Studies
Pregnancy	Contraindication	Low certainty	Counts toward the caffeine limit. Preparation or compound: Green tea (caffeine)	^{36 35}
Iron-deficiency anemia	Adverse effect or risk	Very low certainty	Tea can lower iron absorption; one case report. Preparation or compound: Green tea drink	^{10 8}

I. Biomarkers

Connected to	Kind of connection	Evidence status	Context	Studies
LDL cholesterol	Biological association	Low certainty	Measured in trials: lowered. A lab change is not the same as a health benefit.	^{32 11 7}
Systolic blood pressure	Biological association	Low certainty	Measured in trials: lowered. A lab change is not the same as a health benefit.	^{26 11 7}
Body weight	Biological association	Low certainty	Measured in trials: unchanged. A lab change is not the same as a health benefit.	¹³
Death from any cause	Biological association	Low certainty	Measured in trials: lowered. A lab change is not the same as a health benefit.	^{1 16}
HbA1c	Biological association	Evidence against	Measured in trials: unchanged. A lab change is not the same as a health benefit.	³
Attention and memory tests	Biological association	Low certainty	Measured in trials: raised. A lab change is not the same as a health benefit.	¹⁹

J. Genes, receptors and enzymes

Connected to	Kind of connection	Evidence status	Context	Studies
UGT1A4	Preliminary mechanism	Human	Genotype linked with liver enzyme rises on high-dose extract in one secondary analysis.	²
COMT	Preliminary mechanism	Human	Genotype examined with liver enzyme changes on high-dose extract.	²

L. Active compounds

Connected to	Kind of connection	Evidence status	Context	Studies
Caffeine	Adverse effect or risk	Moderate certainty	Counts toward daily caffeine; see FDA and NHS figures. Preparation or compound: Green tea	^{34 36}
Fluoride		Low certainty	Present in tea infusions; Polish study hazard values below threshold, highest in older low-weight women drinking green tea. Preparation or compound: Tea infusions in general	^{20 24}
Epigallocatechin gallate (EGCG)	Biological association	Human	Liver effects at high supplement doses; other actions not established in the sources read. Preparation or compound: Leaf	^{38 5 31}
Caffeine	Biological association	Human	Stimulant; see Safety tab. Preparation or compound: Leaf	^{39 34}
L-theanine	Biological association	Human	Reviewers link benefits for attention to caffeine and L-theanine together. Preparation or compound: Leaf	^{40 19 21 31}
Tannins and other polyphenols	Biological association	Human	Tea polyphenols lower iron absorption (radio-iron study, black and herb teas). Preparation or compound: Leaf and stem	^{21 10}
Arginine	Biological association	Lab	Authors propose theanine and arginine counter the stimulating effects of caffeine and EGCG (lab indicator only). Preparation or compound: Leaf	³⁰

Each connection is stored with the ingredient, the connected record, the kind of connection, the evidence status, the supporting studies, the preparation or compound involved, and a review date (last reviewed October 25, 2026).

Evidence at a glance: what changed in 4 lab markers

Tap a number to show only those markers. Counts are markers, not people.

Metabolic1 Other21

The evidence

The research centre for Sencha. Every record here was checked against PubMed or the publisher's page; we never list a study we have not verified.

Evidence by outcome

Cholesterol 4 studies Low certainty Blood pressure 3 studies Low certainty Body weight 2 studies Low certainty Cancer risk 3 studies Not enough evidence Heart disease and death rates in drinkers 3 studies Low certainty Attention, memory and mood 1 study Low certainty Flow and steady alertness during mental tasks 1 study Very low certainty Stress relief (lab chemistry only) 2 studies Not enough evidence Dementia and memory loss risk 2 studies Very low certainty Staying independent in older age (functional disability) 1 study Low certainty Blood sugar in type 2 diabetes 1 study Evidence against

Bars show how many studies we found for each outcome, not how well it works. People are added up across trials only (reviews are not added, to avoid double counting).

How we rate evidence

High certainty

Several well-run trials or reviews agree; further research is unlikely to change the picture much.

Moderate certainty

Good trials point the same way, but some doubt remains.

Low certainty

Small, short or inconsistent trials. The finding could change with better research.

Very low certainty

Very little or very weak human data. Treat as a possibility only.

Mixed findings

Trials or reviews disagree with each other.

Not enough evidence

Not enough human research to say either way.

Evidence against

Good research found no benefit, or found harm.

We take the reviewers' own risk-of-bias and GRADE statements where they exist, and otherwise judge from study size, design, consistency, directness and whether a product matches what is sold. Many publications do not make evidence high. Method note: We searched PubMed and read the abstracts of about 30 sources, read the NCCIH and NHS pages in full, carried over the FDA, EMA and IARC records from our green tea profile, checked the plant name in GBIF, and looked for LiverTox and LactMed (summary records read; the full LiverTox page was not opened). Only abstracts were read for papers. Certainty ratings are the compiler's own reading. Industry links are flagged where we saw them (a tea company in one trial; a supplement company behind one safety review). No study is cited that we could not verify.

Study library: every study we checked 41

Design Research type Year from Search

Study	Design	People	Product, dose, length	Result
Abe 2019 Green tea consumption and mortality in Japanese men and women: a pooled analysis of eight population-based cohort studies in Japan European Journal of Epidemiology · PMID 31392470 · DOI	Pooled cohort	313381 313,381 Japanese adults in eight cohorts; 52,943 deaths over a mean 17.3 years	Green tea drinking (self-reported) leaf (drink) Five or more cups a day versus less than one Mean follow-up 17.3 years · vs Drinking less than 1 cup a day	Five or more cups a day versus less than one: all-cause death HR 0.90 (95% CI 0.87 to 0.94) in men and 0.82 (0.74 to 0.90) in women; heart disease HR 0.82 (0.75 to 0.90) men, 0.75 (0.68 to 0.84) women; stroke-type (cerebrovascular) HR 0.76 (0.68 to 0.85) men, 0.78 (0.68 to 0.89) women. In women, total cancer death HR 0.89 (0.83 to 0.96) at 1 to 2 cups and 0.91 (0.85 to 0.98) at 3 to 4 cups. Lower death rates among heavy green tea drinkers (an association) (All-cause HR 0.90 (0.87, 0.94) men; 0.82 (0.74, 0.90) women) Methods, limits and funding Outcomes: Deaths from all causes, heart disease, stroke, cancer, respiratory disease Limitations: Observational: tea drinkers may differ in diet, exercise and health; Japanese data may not apply elsewhere; sencha not named Funding and conflicts: Not stated in the abstract Read: abstract
Acosta 2023 Hepatotoxicity with High-Dose Green Tea Extract: Effect of Catechol-O-Methyltransferase and Uridine 5-Diphospho-glucuronosyltransferase 1A4 Genotypes Journal of Dietary Supplements · PMID 36178169 · DOI	Controlled trial	1075 Postmenopausal women in the Minnesota Green Tea Trial (400 in the extract group), mean age 59.8 years	High-dose green tea extract capsules (843 mg/day EGCG) versus placebo capsules extract 843 mg/day EGCG 12 months · vs Placebo capsules	This is a secondary analysis. In the extract group, women with the UGT1A4 (rs6755571) A/C variant had larger rises in ALT (about +78% and +82% at months 6 and 9) than women with C/C (about +28% and +30%). The authors suggest this variant may be a risk factor for meaningful liver enzyme rises with 6 to 9 months of high-dose extract. Genes may affect who gets liver enzyme rises on high-dose extract (ALT change differences p<0.001 and p=0.004 (months 6 and 9)) Methods, limits and funding Outcomes: Liver enzymes by gene variant Limitations: Secondary analysis; mostly white women; extract only; not about tea Funding and conflicts: Not stated in the abstract Read: abstract
Asbaghi 2021 Effect of green tea on glycemic control in patients with type 2 diabetes mellitus: A systematic review and meta-analysis Diabetes & Metabolic Syndrome · PMID 33285391 · DOI	Meta-analysis	14 randomised trials in people with type 2 diabetes	Green tea supplementary intake Differed Differed · vs Control	Supplementary green tea had no significant effect on fasting glucose, fasting insulin, HbA1c or HOMA-IR. No significant effect found Methods, limits and funding Outcomes: Fasting glucose, fasting insulin, HbA1c, HOMA-IR Limitations: Small trials; the abstract does not say whether the trials used drink or extract; no effect found is not proof of no effect Funding and conflicts: Not stated in the abstract Read: abstract
Cook 2016 The determination of Fukushima-derived cesium-134 and cesium-137 in Japanese green tea samples and their distribution subsequent to simulated beverage preparation Journal of Environmental Radioactivity · PMID 26714059 · DOI	Lab analysis food	Commercially available Japanese-origin green tea products tested by Health Canada's Radiation Protection Bureau	Japanese green tea, leaf and simulated brewing leaf	Trace amounts of radiocesium were found in Japanese green tea products, with a ratio pointing to the 2011 Fukushima accident. About 64% of the radiocesium came out into the brewed drink. The estimated yearly dose from drinking tea made from the most contaminated samples (1.8 to 3.7 microsieverts) was called insignificant compared with natural radiation, and the authors said there is no health concern at the levels found. Trace radiocesium found; estimated dose judged insignificant by the authors (Not applicable) Methods, limits and funding Outcomes: Radiocesium (cesium-134 and cesium-137) Limitations: Only the most contaminated samples were modelled; samples date from after 2011; abstract only Funding and conflicts: Government radiation laboratory; no conflict statement in the abstract Read: abstract
EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS) 2018 Scientific opinion on the safety of green tea catechins EFSA Journal · PMID 32625874 · DOI	Regulatory opinion	Review of published studies, authority reports and submitted data	Green tea infusions, reconstituted drinks and food supplements containing catechins leaf (drink) and extract EGCG intake from infusions in the EU and from supplements (the figures are in the opinion)	Catechins from traditionally prepared green tea infusions, and reconstituted drinks of the same composition, are in general considered safe at the intakes reported in EU countries. Rare cases of liver injury have been reported after infusions, most probably an idiosyncratic (individual) reaction. Clinical trials show that high-dose EGCG taken as a food supplement raised liver enzymes (serum transaminases) compared with control. Drink generally safe at usual intakes; high-dose supplements raise liver enzymes Methods, limits and funding Outcomes: Liver safety of catechins (EGCG) Limitations: Abstract only was read; the full opinion could not be opened Funding and conflicts: Regulator opinion Read: abstract
Filippini 2020 Green tea (Camellia sinensis) for the prevention of cancer Cochrane Database of Systematic Reviews · PMID 32118296 · DOI	Systematic review	142 studies: 11 randomised trials (1795 people, green tea extract versus placebo) and 131 observational studies (over 1,100,000 people)	Green tea extract in trials; drinking green tea in observational studies leaf (drink) and extract Differed Differed · vs Placebo (trials); lowest intake (cohorts)	Trials of extract (low-certainty): prostate cancer RR 0.50 (95% CI 0.18 to 1.36), gynaecological cancer RR 1.50 (0.41 to 5.48), non-melanoma skin cancer RR 1.00 (0.06 to 15.92). Observational, highest versus lowest intake: overall cancer incidence RR 0.83 (0.65 to 1.07, three studies); cancer death RR 0.99 (0.91 to 1.07, eight studies); both low-certainty. Results conflicted by study design for oesophageal, prostate and urinary cancers and leukaemia. The authors call the evidence limited and inconsistent. Extract side effects included stomach and gut problems, raised liver enzymes and, more rarely, insomnia, raised blood pressure and skin reactions. No clear effect on cancer risk; inconsistent (Prostate RR 0.50 (0.18, 1.36); cancer incidence RR 0.83 (0.65, 1.07); cancer mortality RR 0.99 (0.91, 1.07)) Methods, limits and funding Outcomes: Cancer incidence and death, adverse effects, quality of life Limitations: Most studies in Asian populations who drink a lot of green tea; observational studies cannot prove cause; trials used extract Funding and conflicts: Non-US government support listed in PubMed record Read: abstract
Hartley 2013 Green and black tea for the primary prevention of cardiovascular disease Cochrane Database of Systematic Reviews · PMID 23780706 · DOI	Systematic review	821 11 randomised trials of at least 3 months in healthy adults or adults at high risk of heart disease; 7 trials tested green tea, 4 black tea	Green tea, black tea or tea extracts (doses and forms differed between trials) leaf (drink) and extracts Differed between trials At least 3 months · vs No intervention, placebo or minimal intervention	No trial reported heart or blood vessel events. Green tea: total cholesterol -0.62 mmol/L (95% CI -0.77 to -0.46), LDL cholesterol -0.64 mmol/L (-0.77 to -0.52), systolic blood pressure -3.18 mmHg (-5.25 to -1.11), diastolic -3.42 (-4.54 to -2.30). The authors say only a small number of studies contributed and the green tea results were not stable to sensitivity analysis. Adverse events in five trials were judged unlikely to be due to the tea. Small lowering of cholesterol and blood pressure, unstable (TC MD -0.62 (-0.77, -0.46); LDL MD -0.64 (-0.77, -0.52); SBP MD -3.18 (-5.25, -1.11)) Methods, limits and funding Outcomes: Heart disease events, blood pressure, cholesterol Limitations: Few trials per analysis, risk of bias, forms and doses mixed (drink and extract); no long-term follow-up Funding and conflicts: Non-US government support listed in PubMed record; no industry funding stated in the abstract Read: abstract
He 2024 Severe iron-deficiency anemia after short-term moderate consumption of green tea in woman: A rare case report Heliyon · PMID 39263133 · DOI	Case report	1 One woman who drank moderate amounts of green tea for about three months	Green tea drink leaf (drink) Moderate (amount not given in the abstract) About 3 months	Haemoglobin fell by 6.9 g/dl with severe iron-deficiency anemia. After she changed her tea habits there was no recurrence. The authors say clinicians should know even moderate tea intake can cause severe anemia in people who are especially vulnerable to its effect on iron absorption. One reported case of severe anemia Methods, limits and funding Outcomes: Haemoglobin Limitations: Single case; other causes of iron loss are not described in the abstract Funding and conflicts: Not stated Read: abstract
Hu 2018 The safety of green tea and green tea extract consumption in adults - Results of a systematic review Regulatory Toxicology and Pharmacology · PMID 29580974 · DOI	Systematic review	Toxicology studies and adverse-event data from 159 human intervention studies	Brewed green tea, green tea in drinks or food, and concentrated catechin-rich preparations leaf (drink) and extract	Liver was the target organ. Liver adverse events in humans came from a limited range of concentrated, catechin-rich preparations taken as large single doses, and not from brewed tea or extracts used in drinks or food. The authors derived a safe intake level for adults for solid single-dose preparations and a separate, higher observed safe level for beverage forms (the numbers are in the paper). Liver effects tied to concentrated bolus-dose preparations, not brewed tea Methods, limits and funding Outcomes: Liver adverse events Limitations: Abstract only was read; the abstract does not state who funded the review Funding and conflicts: Industry-linked: all three first authors are at Herbalife Nutrition (affiliations in the abstract); the fourth is an independent consultant Read: abstract
Hurrell 1999 Inhibition of non-haem iron absorption in man by polyphenolic-containing beverages British Journal of Nutrition · PMID 10999016	Controlled trial	Adult volunteers given a bread meal with radio-labelled iron	Black tea, herb teas (chamomile, vervain, lime flower, pennyroyal, peppermint), coffee and cocoa leaf (drink) Test beverages with different polyphenol amounts Single meals · vs Water control meal	All the beverages reduced iron absorption in a way that depended on their polyphenol content. Black tea cut absorption by 79 to 94 percent, peppermint tea 84, pennyroyal 73, cocoa 71, vervain 59, lime flower 52 and camomile 47 percent. Milk made little difference. Green tea was NOT tested. Large drop in iron absorption from a meal Methods, limits and funding Outcomes: Iron absorption from the meal Limitations: Green tea not tested; single meals in adults; applying this to green tea is an inference Funding and conflicts: Non-US government support listed in PubMed record Read: abstract
Igho-Osagie 2020 Short-Term Tea Consumption Is Not Associated with a Reduction in Blood Lipids or Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials Journal of Nutrition · PMID 33188386 · DOI	Meta-analysis	798 14 randomised trials in healthy adults and at-risk adults (obesity, prediabetes, borderline high cholesterol, metabolic syndrome)	Green tea or black tea leaf (drink) Differed 4 to 24 weeks (mean 7.4) · vs Placebo or control	No significant effect of tea on systolic or diastolic blood pressure, total, LDL or HDL cholesterol or triglycerides. Strength of evidence was low to moderate because the studies were small and underpowered. No significant effect in short trials (No significant effects (intervals not given in the abstract)) Methods, limits and funding Outcomes: Blood pressure, total, LDL and HDL cholesterol, triglycerides Limitations: Small trials, short duration, green and black tea pooled; absence of effect is not proof of no effect Funding and conflicts: Non-US government support listed in PubMed record Read: abstract
Jayasingha 2025 Fluoride in tea: accumulation, dietary exposure, and future strategies for risk mitigation in food safety; a scoping review Critical Reviews in Food Science and Nutrition · PMID 40504749 · DOI	Scoping review lab/food analysis	88 studies worldwide on fluoride in tea	Tea (all types) leaf (drink)	Tea plants take up fluoride from soil. Longer brewing released more fluoride. Average levels by type were brick tea 4.78 mg/L, black tea 2.73, green tea 1.37, white tea 0.49 and herbal tea 0.17. The review says black tea poses risks for children and for adults in high-intake regions; excessive intake may cause tooth and bone fluorosis and kidney disease. Green tea has less fluoride than black or brick tea but more than white or herbal tea Methods, limits and funding Outcomes: Fluoride in brewed tea Limitations: Scoping review; averages mix many countries; local water also adds fluoride Funding and conflicts: Not stated Read: abstract
Jurgens 2012 Green tea for weight loss and weight maintenance in overweight or obese adults Cochrane Database of Systematic Reviews · PMID 23235664 · DOI	Systematic review	Randomised trials of at least 12 weeks in overweight or obese adults; six trials outside Japan (532 people) and eight in Japan (1030 people)	Green tea preparations (drink and extracts) leaf (drink) and extracts Differed 12 to 13 weeks · vs Control	Outside Japan: weight difference -0.04 kg (95% CI -0.5 to 0.4), BMI -0.2 kg/m2 (-0.5 to 0.1), waist -0.2 cm (-1.4 to 0.9). The eight Japanese trials were too different to pool; weight differences ranged from -0.2 to -3.5 kg. Adverse events in four of eight trials that recorded them were mild to moderate; two needing hospital care were reported as not related. Almost no weight change outside Japan; mixed results in Japanese trials (Weight MD -0.04 kg (-0.5, 0.4) outside Japan) Methods, limits and funding Outcomes: Weight, BMI, waist circumference, adverse events Limitations: Short trials; green tea preparations of many kinds; not a drink-only result Funding and conflicts: Non-US government support listed in PubMed record Read: abstract
Kakutani 2019 Green Tea Intake and Risks for Dementia, Alzheimer's Disease, Mild Cognitive Impairment, and Cognitive Impairment: A Systematic Review Nutrients · PMID 31137655 · DOI	Systematic review	3 cohort studies and 5 cross-sectional studies	Green tea drinking leaf (drink) · vs Lower or no intake	One cohort and three cross-sectional studies supported a benefit, one cohort and one cross-sectional partly supported it, and one cohort and one cross-sectional found no association. The authors say well-designed cohort studies are needed. Mixed observational results Methods, limits and funding Outcomes: Dementia, Alzheimer disease, mild cognitive impairment, cognitive impairment Limitations: Observational only; small number of studies; cannot show cause Funding and conflicts: Not stated in the abstract Read: abstract
Kawahara 2024 Chromosome-Scale Genome Assembly and Characterization of Top-Quality Japanese Green Tea Cultivar 'Seimei' Plant and Cell Physiology · PMID 38807462 · DOI	Genome study plant	Genome of the tea cultivar 'Seimei' and 23 Japanese cultivars	Japanese tea plant leaf	The introduction says Japanese green tea is characterised by initial steaming of freshly harvested leaves, which inactivates enzymes such as polyphenol oxidases and so produces sencha, gyokuro and matcha that keep a vibrant green colour. The paper itself is about the plant's genome. Used here only for the description of steaming (Not applicable) Methods, limits and funding Outcomes: Genome sequence Limitations: Plant genetics paper; the steaming description is background, not a finding Funding and conflicts: No conflict statement read in the abstract Read: abstract
Kuriyama 2006 Green tea consumption and mortality due to cardiovascular disease, cancer, and all causes in Japan: the Ohsaki study JAMA · PMID 16968850 · DOI	Prospective cohort	40530 40,530 Japanese adults aged 40 to 79 without stroke, heart disease or cancer at the start (Ohsaki National Health Insurance cohort, from 1994); follow-up up to 11 years; 4,209 deaths	Green tea drinking (self-reported cups per day) leaf (drink) Less than 1 cup a day compared with 1 to 2, 3 to 4, and 5 or more cups a day Up to 11 years (all causes) and up to 7 years (cause-specific) · vs Drinking less than 1 cup a day	All-cause death, 5 or more cups versus under 1: men HR 0.88 (95% CI 0.79 to 0.98), women HR 0.77 (0.67 to 0.89). Cardiovascular death in women: HR 0.69 (0.53 to 0.90) at 5 or more cups. The strongest link was with stroke death. Cancer death was not significantly different from 1.00 in any group. Lower all-cause and cardiovascular death in heavier drinkers, stronger in women; no link with cancer death (an association) (All-cause HR 0.88 (0.79, 0.98) men; 0.77 (0.67, 0.89) women) Methods, limits and funding Outcomes: Deaths from all causes, cardiovascular disease and cancer Limitations: Observational: tea drinkers may differ in diet, exercise and health; intake self-reported once at the start; Japanese adults; the type of green tea (such as sencha) is not named in the abstract Funding and conflicts: Funding not stated in the abstract (research-support listing says non-US government) Read: abstract
Kuriyama 2006 Green tea consumption and cognitive function: a cross-sectional study from the Tsurugaya Project 1 American Journal of Clinical Nutrition · PMID 16469995 · DOI	Cross sectional	1003 1,003 Japanese adults aged 70 or older in a community health check (Tsurugaya Project), assessed in 2002	Green tea drinking (self-reported) leaf (drink) Up to 3 cups a week; 4 to 6 cups a week or 1 a day; 2 or more cups a day Single time point (cross-sectional) · vs 3 cups a week or fewer	At the under-26 cutoff, 2 or more cups a day: odds ratio 0.46 (95% CI 0.30 to 0.72), trend P=0.0006. No clear link for black or oolong tea (OR 0.87, 0.55 to 1.38) or coffee (OR 1.03, 0.59 to 1.80) at the top level. Higher green tea drinking linked to lower prevalence of cognitive impairment (an association at one point in time) (2 or more cups OR 0.46 (0.30, 0.72)) Methods, limits and funding Outcomes: Cognitive impairment on the Mini-Mental State Examination Limitations: Cross-sectional: cannot show which came first (people with poorer memory may drink less tea); self-reported intake Funding and conflicts: Funding not stated in the abstract Read: abstract
Kurosaka 2025 Green tea consumption rapidly enhances cognitive performance and flow state during mental tasks in healthy young adults PLoS One · PMID 40638646 · DOI	Crossover trial	22 22 healthy young Japanese men, mean age 21.9	Green tea drink (type not named in the abstract) leaf (drink) Three small sips totalling 210 mL, compared with water and no drink Single session · vs Water and no beverage	No significant difference in task accuracy between conditions (ceiling effects, accuracy above 95%). With tea, arousal was kept up and mental fatigue did not rise, unlike the other conditions. Flow score was higher with tea than with no drink (p=0.0009); the task felt shorter (p=0.0016 vs no drink). More flow and steady arousal on self-report; no change in accuracy (Not given in the abstract) Methods, limits and funding Outcomes: Task performance, mental fatigue, workload, flow experience Limitations: Very small, men only, young, a single short session, mostly self-rated measures; accuracy could not differ because it was near perfect Funding and conflicts: Industry-linked: authors from ITOEN Ltd (a tea company); one author reports consultant honoraria from the funding company Read: abstract
Mancini 2017 Green tea effects on cognition, mood and human brain function: A systematic review Phytomedicine · PMID 28899506 · DOI	Systematic review	21 studies: 4 randomised trials, 12 crossover studies, 4 cross-sectional studies and 1 cohort	Green tea, green tea extract, L-theanine or EGCG leaf (drink), extract and isolated compounds Differed Differed · vs Differed	The reviewers found evidence that green tea influences psychological symptoms (for example less anxiety), cognition (for example memory and attention) and brain function (for example working-memory activation on brain scans). Benefits on cognition were seen with caffeine and L-theanine together, with less effect from either alone, so the effect cannot be put down to one ingredient. Possible small effects on attention and memory Methods, limits and funding Outcomes: Anxiety and mood, memory and attention, brain activity Limitations: Mixes drink, extract and isolated compounds; many short or single-dose studies; PubMed only; quality scores are the reviewers own Funding and conflicts: Not stated in the abstract Read: abstract
Małyszek 2025 Assessment of Fluoride Intake Risk via Infusions of Commercial Leaf Teas Available in Poland Using the Target Hazard Quotient Index Approach Foods · PMID 40941060 · DOI	Food analysis food	98 98 leaf teas on the Polish market: 55 black, 27 green, 9 oolong, 7 white	Leaf tea infusions leaf	All hazard values for fluoride stayed well below the safety threshold (below 1). The highest values were in elderly, low-body-weight women drinking green tea, so that group may be more vulnerable, and the authors say older adults, especially low-weight women, should moderate their intake of high-fluoride teas. Fluoride from leaf tea did not appear to pose a direct health risk overall (Not applicable) Methods, limits and funding Outcomes: Fluoride and a hazard index Limitations: Modelling from measured samples; Polish market; Japanese tea types not named; abstract only Funding and conflicts: Authors declare no conflicts of interest Read: abstract
NICHD / 2006 Drugs and Lactation Database (LactMed): Green Tea LactMed (NCBI Bookshelf) · PMID 30000907	Database record	n/a	Green tea leaves and stems leaf and stem	Green tea leaves and stems contain caffeine, L-theanine, polyphenols and tannins. Fussiness, jitteriness and poor sleep have been reported in infants of mothers with extremely high caffeine intakes. Giving tea directly to infants can interfere with iron absorption and cause anemia, but anemia in breastfed infants has not been reported with maternal tea intake. Passage of L-theanine into breastmilk has not been studied. No studies of oral green tea extract in breastfeeding were found. No clear harm from usual maternal tea intake; caution at very high caffeine Methods, limits and funding Outcomes: Breastfeeding safety Limitations: Summary record; no new data Funding and conflicts: Public database Read: abstract
NIDDK 2012 LiverTox: Green Tea (Clinical and Research Information on Drug-Induced Liver Injury) LiverTox (NCBI Bookshelf) · PMID 31643260	Database record	n/a	Green tea extract and, more rarely, large amounts of green tea leaf and extract	Green tea extract and, more rarely, ingestion of large amounts of green tea have been implicated in cases of clinically apparent acute liver injury, including instances of acute liver failure and either need for urgent liver transplantation or death. Rare but serious liver injury, mostly with extract Methods, limits and funding Outcomes: Drug-induced liver injury Limitations: Only the PubMed summary was read; the full LiverTox page was not opened Funding and conflicts: Public database Read: abstract
Nakamura 2022 Comprehensive analysis of a decade of cumulative radiocesium testing data for foodstuffs throughout Japan after the 2011 Fukushima Daiichi Nuclear Power Plant accident PLoS One · PMID 36129916 · DOI	Monitoring data analysis food	More than 2.5 million foodstuff samples tested in Japan, fiscal years 2012 to 2021	Japanese foodstuffs including soft drinks made with tea food and drink	13 samples in the category 'drinking water including soft drinks containing tea as a raw material' (tested in fiscal year 2012) exceeded the limit of 10 Bq/kg. More than 99% of monitored foodstuffs were low and not above the limit in recent years, except hard-to-manage items such as wild mushrooms, plants, animals and fish. Routine national testing; tea-based drinks over the limit were few and from the first year (Not applicable) Methods, limits and funding Outcomes: Radiocesium against Japan's legal limits Limitations: Gives tea-drink counts only for fiscal year 2012; not specific to sencha; abstract only Funding and conflicts: Authors declare no competing interests Read: abstract
Pavlovič 2023 Fluoride and Aluminium in Tea (Camellia sinensis L.)-Tea Quality Indicators and Risk Factors for Consumers Molecules · PMID 37687225 · DOI	Food analysis food	35 35 commercial black and green teas sold in Slovenia, tested as infusions	Black and green tea infusions (leaf and filter bags) leaf	Fluoride ranged from 0.34 to 4.79 mg/L and aluminium from 0.51 to 8.90 mg/L. Averages ran black filter, then green filter, then black leaves and green leaves about equal. The authors say daily consumption of larger quantities (about 1 L) of teas with high fluoride and aluminium could potentially pose a health risk. Fluoride and aluminium are present in tea infusions; levels vary by product (Not applicable) Methods, limits and funding Outcomes: Fluoride and aluminium in infusions Limitations: European market teas, no Japanese teas named; abstract only Funding and conflicts: Authors declare no competing interests Read: abstract
Pillukat 2014 Concentrated green tea extract induces severe acute hepatitis in a 63-year-old woman - a case report with pharmaceutical analysis Journal of Ethnopharmacology · PMID 24862489 · DOI	Case report	1 A 63-year-old woman taking green tea capsules on the advice of a cancer support group	Concentrated green tea extract capsules (EGCG 93.2% of the catechins found) extract Very high EGCG dose level per the analysis	Severe hepatitis assessed as probably caused by the capsules (CIOMS/RUCAM score). The liver tissue pattern fit drug-induced hepatitis and other causes were excluded. After stopping, and a treatment called albumin dialysis, she recovered quickly and fully. Lab analysis of the capsules found no contaminants. Severe but reversible liver injury linked to concentrated extract Methods, limits and funding Outcomes: Liver injury Limitations: Single case; extract, not brewed tea Funding and conflicts: Not stated Read: abstract
Rezaei 2025 Effect of green tea supplementation on blood pressure in adults: a GRADE-assessed systematic review and dose-response meta-analysis of randomised controlled trials Blood Pressure · PMID 40497293 · DOI	Meta-analysis	36 randomised trials in adults	Green tea supplementation (forms not broken out in the abstract) Not given here Studies of 8 weeks or less showed stronger effects · vs Control or placebo	Systolic blood pressure fell by 1.08 mmHg (95% CI -1.98 to -0.18; I2 85%) and diastolic by 1.09 mmHg (-1.67 to -0.50; I2 74%). Effects were stronger in people with raised starting blood pressure, shorter studies, Asian populations and women. No clear link between size of change and dose or duration. The authors call green tea a complementary approach, not a treatment. Very small average blood pressure drop with large differences between studies (SBP -1.08 (-1.98, -0.18); DBP -1.09 (-1.67, -0.50)) Methods, limits and funding Outcomes: Systolic and diastolic blood pressure Limitations: Very high heterogeneity; the abstract does not separate drink from extract; the GRADE rating is not given in the abstract Funding and conflicts: Not stated in the abstract Read: abstract
Rodriguez 2020 Human exposure to fluoride from tea (Camellia sinensis) in a volcanic region - Canary Islands, Spain Environmental Science and Pollution Research · PMID 32740848 · DOI	Food analysis lab/food analysis	90 90 tea samples (Canary Islands)	Mixed, black and other teas prepared with local tap water leaf (drink) Two 250 mL cups a day assumed	Mixed teas (2.82 mg/L) and black teas (2.28 mg/L) had the highest fluoride. Two daily cups of those teas made with local tap water would give children aged 4 to 8 a large share (74.4% and 63.6%) of the EFSA upper intake level. The authors advise less tea for children and in pregnancy. Fluoride in tea can matter for young children in some regions Methods, limits and funding Outcomes: Fluoride in tea Limitations: Local water and region; green tea results are not given in the abstract Funding and conflicts: Not stated Read: abstract
Taylor 1999 Probable antagonism of warfarin by green tea Annals of Pharmacotherapy · PMID 10332534 · DOI	Case report	1 A 44-year-old man with a mechanical aortic heart valve taking warfarin	Green tea drink leaf (drink) Half a gallon to a gallon of green tea a day for about a week About 1 week before the low reading	The INR fell from 3.79 to 1.37 about three weeks later, and was 1.14 a month after. He had started drinking one-half to one gallon of green tea a day about a week before the INR of 1.37. After stopping the tea the INR rose to 2.55. The authors suggested vitamin K in the tea. A drop in warfarin effect linked in time to a very large amount of green tea (INR 3.79 to 1.37) Methods, limits and funding Outcomes: Blood clotting test (INR) Limitations: One case; cannot prove cause; very large amount of tea; vitamin K content was not measured Funding and conflicts: Not stated Read: abstract
Tomata 2012 Green tea consumption and the risk of incident functional disability in elderly Japanese: the Ohsaki Cohort 2006 Study American Journal of Clinical Nutrition · PMID 22277550 · DOI	Prospective cohort	13988 13,988 Japanese adults aged 65 or older; 3-year follow-up; 9.4% (1,316) developed functional disability	Green tea drinking (self-reported cups per day) leaf (drink) Under 1 cup a day compared with 1 to 2, 3 to 4, and 5 or more cups a day 3 years · vs Drinking less than 1 cup a day	Compared with under 1 cup a day: HR 0.90 (0.77 to 1.06) for 1 to 2 cups, 0.75 (0.64 to 0.88) for 3 to 4 cups, 0.67 (0.57 to 0.79) for 5 or more cups (trend P<0.001), after adjustment. Lower risk of later disability among heavier green tea drinkers (an association) (5 or more cups HR 0.67 (0.57, 0.79)) Methods, limits and funding Outcomes: Incident functional disability (needing long-term care insurance support) Limitations: Observational; short follow-up; self-reported intake; healthier people may drink more tea; tea type not named Funding and conflicts: Funding not stated in the abstract Read: abstract
Unno 2025 Stress-Relieving Effects of Japanese Green Tea: Evaluation Using the Molar Ratio of Caffeine and Epigallocatechin Gallate to Theanine and Arginine as an Indicator Foods · PMID 39796392 · DOI	Lab analysis lab	Tea leaves and infusions of Japanese green teas on sale in 2022, mostly first crop; includes sencha, gyokuro and tamaryokucha	Japanese green tea leaf and infusion (chemical analysis) leaf (analysed in the lab)	Sencha, gyokuro and tamaryokucha had a ratio (caffeine plus EGCG compared with theanine plus arginine) below 3, which the authors expect to go with a stress-relieving effect. Most amino acids came out in the first and second infusions, so no such effect was expected after the third cup. A chemical indicator only; no people were tested (Not applicable) Methods, limits and funding Outcomes: Content of caffeine, EGCG, theanine and arginine Limitations: Lab composition and a proposed indicator, not a trial in people; the authors have shown the link with stress in other work that this abstract does not detail Funding and conflicts: Authors declare no conflicts of interest Read: abstract
Unno 2026 Compositional Diversity and Functional Interactions of Bioactive Compounds in Japanese Green Tea: Focus on Matcha, Sencha, and Gyokuro Molecules · PMID 42654013 · DOI	Narrative review review	Narrative review of Japanese green teas (matcha, sencha, gyokuro)	Japanese green tea leaf	Says Japanese green teas come from Camellia sinensis and contain catechins, caffeine and the amino acid theanine, and that amounts differ with harvest season, cultivar and cultivation. For sencha, composition also differs with water temperature and steeping time. The authors expect these differences to affect the body's responses. Describes variation; no health outcome measured (Not applicable) Methods, limits and funding Outcomes: Composition and how compounds interact Limitations: Narrative review; abstract only was read Funding and conflicts: Authors declare no conflicts of interest Read: abstract
Zheng 2011 Green tea intake lowers fasting serum total and LDL cholesterol in adults: a meta-analysis of 14 randomized controlled trials American Journal of Clinical Nutrition · PMID 21715508 · DOI	Meta-analysis	1136 14 randomised trials in adults	Green tea beverage or green tea extract leaf (drink) and extract Differed Differed · vs Control	Total cholesterol lowered by 7.20 mg/dL (95% CI -8.19 to -6.21) and LDL cholesterol by 2.19 mg/dL (-3.16 to -1.21); HDL cholesterol did not change significantly. The authors say changes were not influenced by type of intervention, dose, duration, health status or study quality. Small average drop in total and LDL cholesterol (TC -7.20 (-8.19, -6.21) mg/dL; LDL -2.19 (-3.16, -1.21) mg/dL) Methods, limits and funding Outcomes: Total, LDL and HDL cholesterol Limitations: Mixes drinks and extracts; the abstract gives no separate drink-only result; later reviews found no effect in short trials (see Igho-Osagie 2020) Funding and conflicts: Non-US government support listed in PubMed record; funding details not in the abstract Read: abstract
n/a 2016 IARC (WHO): Press release no. 244, coffee, mate and very hot beverages (15 June 2016) n/a · Source	Authoritative guidance n/a	n/a	n/a	IARC classified drinking very hot beverages as probably carcinogenic to humans (Group 2A), based on limited evidence from studies in places where tea or mate is drunk very hot, and said it is the temperature rather than the drink that appears responsible. Methods, limits and funding Outcomes: IARC classified drinking very hot beverages as probably carcinogenic to humans (Group 2A), based on limited evidence from studies in places where tea or mate is drunk very hot, and said it is the temperature rather than the drink that appears responsible. Limitations: Press release read from the PDF on 2026-10-25; the exact temperature figure could not be read from the extracted text, so it is not quoted here. Read: full-text
n/a 2024 FDA: Spilling the Beans: How Much Caffeine Is Too Much? (content current as of 28 Aug 2024) n/a · Source	Authoritative guidance n/a	n/a	n/a	Lists green tea at 37 mg caffeine per 12 fl oz drink. Cites 400 mg a day as an amount not generally linked with negative effects in most adults, with wide differences in sensitivity. Lists signs of too much caffeine (faster heart rate, palpitations, high blood pressure, insomnia, anxiety, jitters, upset stomach, nausea, headache). Says caffeinated drinks should be avoided for children younger than age 2 (quoting the Dietary Guidelines) and that pregnant or breastfeeding people should talk to a health professional. Methods, limits and funding Outcomes: Lists green tea at 37 mg caffeine per 12 fl oz drink. Cites 400 mg a day as an amount not generally linked with negative effects in most adults, with wide differences in sensitivity. Lists signs of too much caffeine (faster heart rate, palpitations, high blood pressure, insomnia, anxiety, jitters, upset stomach, nausea, headache). Says caffeinated drinks should be avoided for children younger than age 2 (quoting the Dietary Guidelines) and that pregnant or breastfeeding people should talk to a health professional. Limitations: Consumer guidance page, not a trial. Read in full on 2026-10-25. Read: full-text
n/a 2025 NCCIH (NIH): Green Tea: Usefulness and Safety (last updated February 2025) n/a · Source	Authoritative guidance n/a	n/a	n/a	Says definite conclusions cannot yet be reached on whether green tea helps for most uses. Cancer results inconsistent; lower heart disease risk seen in Asian but not Western groups; small cholesterol drops mostly from extract trials; no safety concerns reported for green tea as a drink in adults; liver injury uncommon and mostly with extract tablets or capsules; interactions with nadolol (high-dose green tea), atorvastatin (extract) and raloxifene; keep caffeine moderate in pregnancy. Methods, limits and funding Outcomes: Says definite conclusions cannot yet be reached on whether green tea helps for most uses. Cancer results inconsistent; lower heart disease risk seen in Asian but not Western groups; small cholesterol drops mostly from extract trials; no safety concerns reported for green tea as a drink in adults; liver injury uncommon and mostly with extract tablets or capsules; interactions with nadolol (high-dose green tea), atorvastatin (extract) and raloxifene; keep caffeine moderate in pregnancy. Limitations: A regulator-style fact sheet, not a trial. Page text read in full on 2026-10-25. Read: full-text
n/a 2026 NHS (UK): Foods to avoid in pregnancy (page last reviewed 15 June 2026) n/a · Source	Authoritative guidance n/a	n/a	n/a	Says you should not have more than 200 mg of caffeine a day in pregnancy, estimates about 75 mg in a cup of tea such as black or green tea, and says too much caffeine has been linked to a higher chance of miscarriage and stillbirth. Methods, limits and funding Outcomes: Says you should not have more than 200 mg of caffeine a day in pregnancy, estimates about 75 mg in a cup of tea such as black or green tea, and says too much caffeine has been linked to a higher chance of miscarriage and stillbirth. Limitations: Public-health guidance, not a trial. Read in full on 2026-10-25. The per-cup figure is an estimate. Read: full-text
n/a 2026 EMA: Camelliae sinensis non fermentatum folium (green tea), herbal medicinal product page n/a · Source	Authoritative guidance n/a	n/a	n/a	Page lists Camellia sinensis (L.) Kuntze, non fermentatum folium (green tea), therapeutic area "Fatigue and weakness", status "Assessment finalised", outcome "European Union herbal monograph". Documents: final EU herbal monograph (EMA/HMPC/283630/2012, published 29 April 2014), assessment report and an addendum to the assessment report (EMA/HMPC/30571/2022, published 26 September 2022). Methods, limits and funding Outcomes: Page lists Camellia sinensis (L.) Kuntze, non fermentatum folium (green tea), therapeutic area "Fatigue and weakness", status "Assessment finalised", outcome "European Union herbal monograph". Documents: final EU herbal monograph (EMA/HMPC/283630/2012, published 29 April 2014), assessment report and an addendum to the assessment report (EMA/HMPC/30571/2022, published 26 September 2022). Limitations: Only the web page was read. The monograph and assessment-report PDFs were not opened, so the wording of the monograph is NOT verified. Read: abstract
n/a 2026 PubChem: epigallocatechin gallate (CID 65064), formula C22H18O11 n/a · Source	Database record n/a	n/a	n/a	Compound record confirmed through the PubChem API on 2026-10-25. Methods, limits and funding Outcomes: Compound record confirmed through the PubChem API on 2026-10-25. Limitations: Database record only. Read: full-text
n/a 2026 PubChem: caffeine (CID 2519), formula C8H10N4O2 n/a · Source	Database record n/a	n/a	n/a	Compound record confirmed through the PubChem API on 2026-10-25. Methods, limits and funding Outcomes: Compound record confirmed through the PubChem API on 2026-10-25. Limitations: Database record only. Read: full-text
n/a 2026 PubChem: L-theanine (CID 439378), formula C7H14N2O3 n/a · Source	Database record n/a	n/a	n/a	Compound record confirmed through the PubChem API on 2026-10-25. Methods, limits and funding Outcomes: Compound record confirmed through the PubChem API on 2026-10-25. Limitations: Database record only. Read: full-text
n/a 2026 GBIF Backbone Taxonomy: Camellia sinensis (L.) Kuntze (usage key 3189635), retrieved 2026-10-25 n/a · Source	Database record n/a	n/a	n/a	Accepted species, family Theaceae, order Ericales, genus Camellia. Synonyms listed by the API include Camellia bohea (L.) Sweet, Camellia chinensis (Sims) Kuntze and Camellia cantonensis Lour. Methods, limits and funding Outcomes: Accepted species, family Theaceae, order Ericales, genus Camellia. Synonyms listed by the API include Camellia bohea (L.) Sweet, Camellia chinensis (Sims) Kuntze and Camellia cantonensis Lour. Limitations: Taxonomic database record via the GBIF API. Read: full-text

What we do not know yet

What the evidence supports: large Japanese cohorts link heavy green tea drinking with lower death rates (an association); low-certainty small effects on cholesterol and blood pressure; no clear effect on weight, cancer or blood sugar.
No study read names sencha itself; all human evidence is for green tea in general, and cohort questions do not say which type of green tea was drunk.
No long-term trial of green tea as a drink (not extract) with heart attack, stroke or death as outcomes.
No measured lead, cadmium, arsenic or pesticide values for sencha were found; fluoride and aluminium studies do not name Japanese teas.
No independent source read gives the caffeine in sencha. The EMA monograph and LiverTox full text were not opened; the Health Canada caffeine page did not load.

How new research is added

New studies are found by a saved PubMed search and are placed in a review queue. A person reads each one before it changes any evidence rating or safety wording. New publications never change ratings automatically.

Lab markers

What changed in blood or saliva tests during trials. A changed number is not the same as feeling or being healthier, and we give no "normal ranges".

Metabolic 3

▼

LDL cholesterol

Lowered in trials

The cholesterol carried in the blood that is linked with higher heart disease risk.

Low certainty

Results and what it means

Why it was measured

To see whether green tea changes blood fats.

Statistical vs. clinical meaning

Small and inconsistent; a lab number, not a heart outcome.

Safety implication

None from the numbers; see the Safety tab for extract risks.

Study	Result	People	Product
³²	LDL -2.19 mg/dL (95% CI -3.16 to -1.21)	Adults in 14 trials	Green tea drinks or extracts
¹¹	No significant change in LDL	798 people in 14 trials	Green or black tea, 4 to 24 weeks

^{32 11 7}

●

Body weight

Unchanged in trials

Weight in kilograms.

Low certainty

Results and what it means

Why it was measured

To see whether green tea helps with weight loss.

Statistical vs. clinical meaning

No meaningful change outside Japan.

Safety implication

None.

Study	Result	People	Product
¹³	-0.04 kg (95% CI -0.5 to 0.4) outside Japan; -0.2 to -3.5 kg in Japanese trials, not pooled	Overweight adults, 12 to 13 weeks	Green tea preparations

¹³

●

HbA1c

Unchanged in trials

A blood test that shows average blood sugar over about three months.

Evidence against

Results and what it means

Why it was measured

To see whether green tea helps people with type 2 diabetes.

Statistical vs. clinical meaning

No effect found.

Safety implication

None.

Study	Result	People	Product
³	No significant effect on HbA1c, fasting glucose, insulin or HOMA-IR	14 trials in type 2 diabetes	Green tea supplementation

Other 3

▼

Systolic blood pressure

Lowered in trials

The top number in a blood pressure reading.

Low certainty

Results and what it means

Why it was measured

To see whether green tea changes blood pressure.

Statistical vs. clinical meaning

Very small and varied.

Safety implication

None from the numbers.

Study	Result	People	Product
²⁶	-1.08 mmHg (95% CI -1.98 to -0.18)	36 trials in adults	Green tea supplementation
¹¹	No significant change	798 people in 14 trials	Green or black tea, 4 to 24 weeks

^{26 11 7}

▼

Death from any cause

Lowered in trials

The risk of dying from any cause during follow-up.

Low certainty

Results and what it means

Why it was measured

To see whether heavy green tea drinkers live longer.

Statistical vs. clinical meaning

Observational association only.

Safety implication

None.

Study	Result	People	Product
¹	HR 0.90 (0.87 to 0.94) men; 0.82 (0.74 to 0.90) women, 5+ cups a day versus under 1	313,381 Japanese adults	Self-reported green tea drinking
¹⁶	HR 0.88 (0.79 to 0.98) men; 0.77 (0.67 to 0.89) women, 5+ cups a day versus under 1	40,530 Japanese adults (Ohsaki cohort), up to 11 years	Self-reported green tea drinking

^{1 16}

▲

Attention and memory tests

Raised in trials

Scores on computer or paper tests of attention and working memory.

Low certainty

Results and what it means

Why it was measured

To see whether green tea affects thinking.

Statistical vs. clinical meaning

Possible small effect.

Safety implication

None.

Study	Result	People	Product
¹⁹	Reviewers report better memory and attention with caffeine and L-theanine together; no numbers in the abstract	21 mixed studies	Green tea, extract, L-theanine, EGCG

¹⁹

Safety

What studies and official sources say about side effects, medicines and who should check first. Each point shows what kind of evidence it comes from.

Main points to know 8

A cup of tea and a green tea extract capsule are not the same thing. NCCIH reports no safety concerns for green tea drunk as a beverage by adults, apart from its caffeine. Liver injury is uncommon but has been reported, mostly with concentrated extract in tablets or capsules. EFSA judged traditionally prepared green tea infusions generally safe at the intakes seen in Europe, and found that high-dose EGCG supplements raised liver enzymes in trials. Do not carry safety or benefit results from one form to the other. Authoritative guidance ^{35 5 9}
Rare liver injury, mostly with extract. LiverTox says green tea extract, and more rarely large amounts of green tea, have been linked to clinically apparent liver injury, including liver failure needing transplant or ending in death. EFSA noted rare cases after infusions too, probably an individual reaction. A case report describes severe hepatitis from concentrated extract capsules that cleared after stopping them. Anyone with liver disease, or who has had liver trouble from a supplement, should ask a clinician before any extract. Case report ^{22 5 25}
Caffeine. Green tea contains caffeine. The FDA lists 37 mg in a 12 fl oz drink and says about 400 mg a day is not generally linked with harm in most adults, with wide differences in sensitivity. Too much can cause fast heartbeat, palpitations, high blood pressure, poor sleep, anxiety, jitters, upset stomach, nausea and headache. Authoritative guidance ³⁴
Pregnancy, breastfeeding and young children. The NHS says not to have more than 200 mg of caffeine a day in pregnancy and counts about 75 mg in a cup of black or green tea. NCCIH says to keep caffeine moderate in pregnancy and to ask your provider. LactMed reports fussiness, jitteriness and poor sleep in infants only with extremely high maternal caffeine, and says tea given directly to infants can interfere with iron absorption and cause anemia. The FDA quotes the Dietary Guidelines that caffeinated drinks should be avoided for children younger than age 2. Authoritative guidance ^{36 35 21 34}
Iron. Polyphenols in tea cut iron absorption from a meal in a radio-iron study, but that study did not test green tea. A 2024 case report describes severe iron-deficiency anemia in a woman after about three months of moderate green tea. If you have low iron or anemia, ask a clinician about tea around meals. Human study ^{10 8}
Medicines. NCCIH says high doses of green tea lowered blood levels of the heart medicine nadolol, green tea extract lowered levels of atorvastatin, and an NCCIH-funded study showed an interaction with raloxifene. One 1999 case report links very large amounts of green tea with weaker warfarin effect. Ask your pharmacist if you take any regular medicine. Authoritative guidance ^{35 28}
Very hot drinks. IARC classed drinking very hot beverages as probably carcinogenic to humans (Group 2A) for oesophageal cancer and said it is the temperature, not the drink, that appears responsible. This applies to hot tea as to any other very hot drink; letting a cup cool is a sensible step. Authoritative guidance ³³
Fluoride, aluminium and radioactivity testing. Studies of tea in general found fluoride and aluminium in infusions and a Polish study found the highest fluoride hazard values in older, low-weight women drinking green tea (all still under the safety threshold). Japanese green tea has also been tested for radiocesium since the 2011 Fukushima accident: Health Canada's laboratory found trace amounts in Japanese green tea products and saw no health concern at those levels. No lead, cadmium or pesticide figures for sencha were found. Food analysis ^{20 24 4 23}

Side effects 7

Effect	How often	Severity and recovery	Evidence
Caffeine effects (fast heartbeat, jitters, poor sleep, upset stomach) Listed by the FDA as signs of too much caffeine from any source.	Depends on how much caffeine you take and how sensitive you are; no rate in the sources read	mild to moderate Reversible when caffeine is cut back	Authoritative guidance ³⁴
Nausea, constipation, stomach discomfort and higher blood pressure (extract) NCCIH lists these for green tea extract supplements.	No rate in the sources read	mild Reversible after stopping (not stated)	Authoritative guidance ³⁵
Gut problems, raised liver enzymes, insomnia, raised blood pressure, skin reactions (extract) Cochrane lists these as adverse effects of green tea extract in trials.	Not given in the abstract	mild to moderate Not given	Systematic review ⁶
Liver injury (mostly extract; rarely tea) High-dose extract raised liver enzymes in trials (EFSA, abstract).	Uncommon; no rate found	severe Mostly recovery after stopping; some cases need transplant or are fatal	Case report ^{35 22 25 5}
Lower iron absorption; anemia in a vulnerable person Green tea was not tested in the radio-iron study.	One case report	moderate to severe Improved after changing tea habits	Case report ^{10 8}
Fluoride intake from tea Green tea averaged 1.37 mg/L in a scoping review, below black and brick tea; a Polish study found hazard values below the threshold but highest in older low-weight women drinking green tea.	Depends on tea type, brewing time and local water	not stated not stated	Food analysis ^{12 20 27}
Trace radiocesium in some Japanese teas after 2011 Based on testing; the authors of the Health Canada study found no health concern.	Trace amounts in tested products; 13 tea-based drinks over the limit in 2012	not a health concern at the levels found, per the authors not applicable	Food analysis ^{4 23}

Liver

Liver injury linked to green tea is rare and mostly linked to concentrated extract capsules or tablets. LiverTox says extract, and more rarely very large amounts of tea, have been implicated in acute liver injury, including liver failure needing transplant or death. EFSA found raised liver enzymes with high-dose EGCG supplements in trials and noted rare liver injury after infusions, most probably an unusual individual reaction. A systematic review of 159 human studies found liver events came from concentrated, catechin-rich preparations taken in large single doses, not from brewed tea or extracts used in drinks or food. NCCIH says people with a specific immune-related gene variant seem especially susceptible, and a secondary analysis of a one-year extract trial found liver enzyme rises differed by gene variant. ^{22 5 9 25 2 35}

How often. No rate in tea drinkers or extract users could be found in the sources read.

Monitoring. No monitoring advice was read from an agency. The Safety tab tells readers to stop extract and seek care if liver warning signs appear.

p24862489.

This is a safety connection. It is not evidence that Sencha supports liver health.

Medicines and supplements 6

With	Why it matters	Importance	Evidence	What to do
Warfarin prescription	The case authors suggested vitamin K in the tea could counter warfarin; vitamin K was not measured.	One 1999 case report: INR fell from 3.79 to 1.37 after about a week of half a gallon to a gallon of green tea a day, and rose to 2.55 after stopping. It cannot prove cause and the amount was very large.	Case report Very low certainty ²⁸	Tell your prescriber about any big change in tea habits so your INR can be checked.
Nadolol (beta-blocker) prescription	Not described in the source read.	NCCIH says green tea at high doses reduced blood levels of nadolol and so its effectiveness.	Authoritative guidance Low certainty ³⁵	Ask your pharmacist if you take nadolol.
Atorvastatin (cholesterol medicine) prescription	Not described in the source read.	NCCIH says green tea extract can reduce blood levels of atorvastatin. This is about the extract.	Authoritative guidance Low certainty ³⁵	Ask your pharmacist before taking green tea extract with a statin.
Raloxifene (bone medicine) prescription	Not described in the source read.	NCCIH says a study it funded showed an interaction between green tea and raloxifene. Details were not given.	Authoritative guidance Low certainty ³⁵	Ask your pharmacist.
Iron supplements and iron-poor diets supplement	Tea polyphenols reduce iron absorption in general.	A radio-iron study showed black tea and herb teas cut iron absorption; green tea was not tested, and one case report links moderate green tea with severe anemia.	Human study Low certainty ^{10 8}	If you have low iron, ask a clinician about drinking tea away from meals. Whether that works was not tested in the sources read.
Other sources of caffeine food	Caffeine adds up across coffee, other teas, energy drinks and some supplements.	The FDA says its 400 mg figure is for all caffeine in a day.	Authoritative guidance Moderate certainty ^{34 36}	Count all caffeine sources, especially in pregnancy.

Who should check first 6

Situation	Advice	Evidence
Pregnancy	Green tea is not banned in pregnancy, but it counts toward the daily caffeine limit. No source read covers green tea extract capsules in pregnancy, so ask a clinician before using them.	Authoritative guidance ^{36 35}
Breastfeeding	LactMed reports infant fussiness and poor sleep only with extremely high maternal caffeine. No studies of green tea extract in breastfeeding were found.	Authoritative guidance ²¹
Infants and young children	Do not give tea to infants. LactMed says it can interfere with iron absorption and cause anemia. Avoid caffeinated drinks for children under 2 (FDA, quoting the Dietary Guidelines).	Authoritative guidance ^{21 34}
Liver disease or past liver injury from a supplement	Ask a clinician before using green tea extract capsules or tablets, because of the liver injury reports. The sources read do not give a rule for brewed tea in liver disease.	Precaution from liver reports ^{22 5}
Low iron or anemia	Ask a clinician. Tea can lower iron absorption.	Human study ^{10 8}
Taking warfarin, nadolol, a statin or raloxifene	Ask your pharmacist or prescriber before changing how much green tea or extract you take.	Authoritative guidance ^{28 35}

Overdose, product quality and regulators

Summary. Brewed green tea has no safety concerns reported for adults (NCCIH). The main toxicity concern is the liver, linked to concentrated catechin-rich extract taken in large single doses.

Animal. The Hu systematic review says lab studies show the liver as target organ, strongly tied to dosing conditions such as a large single dose by gavage and fasting, and to total catechin and EGCG content.

Human doses studied. EFSA found that high-dose EGCG taken as a food supplement raised liver enzymes in trials (the threshold is in the opinion). The Minnesota Green Tea Trial gave a high-dose extract for 12 months.

High dose or long term signals. Liver enzyme rises with long high-dose extract use; differences by gene variant in one secondary analysis.

Overdose response. Not described in the sources read.

Genotoxicity. Not read.

Toxic or hazardous parts. Leaf is the part used; stems are also in tea (LactMed). No source read compared other parts.

Sources read measured fluoride, aluminium and radiocesium in tea. None gave lead, cadmium, arsenic or pesticide figures for sencha, so those are unknown here, not shown safe.

Fluoride. Tea plants take up fluoride. A scoping review of 88 studies gave average levels of 1.37 mg/L for green tea, below black and brick tea; longer brewing released more. A Polish study of 98 leaf teas (27 green) found all hazard values for fluoride below the safety threshold, with the highest values in elderly low-weight women drinking green tea. No Japanese tea types were named. ^{12 20 27}

Aluminium. In 35 commercial black and green teas sold in Slovenia, infusions held 0.51 to 8.90 mg/L of aluminium (fluoride 0.34 to 4.79 mg/L). The authors say daily drinking of larger quantities of teas high in fluoride and aluminium could potentially be a health risk. Japanese tea types were not named. ²⁴

Radioactivity after the 2011 Fukushima accident. Health Canada's radiation laboratory found trace radiocesium in Japanese green tea products and about 64% of it came out into the brewed drink; the estimated yearly dose from the most contaminated samples was far below natural radiation and the authors saw no health concern. Japan's own testing of more than 2.5 million foodstuff samples found 13 tea-based soft drink samples above the legal limit in 2012, and more than 99% of monitored foods were low in recent years. ^{4 23}

Heavy metals and pesticides. Lead, cadmium, arsenic and pesticide residue figures for sencha were not found in the sources read. Not described is not proof of none.

Supplement quality. LactMed notes that dietary supplements are not pre-approved by the FDA and labelled and actual ingredients can differ. In the case report, lab analysis of the capsules found no contaminants but a very high EGCG level. ^{21 25}

Body	Action	Date
NCCIH (NIH) (United States)	Says no safety concerns have been reported for green tea as a beverage in adults; lists extract side effects, rare liver injury, medicine interactions and a caffeine caution in pregnancy. Notes the FDA has approved a specific green tea extract ointment as a prescription drug for genital warts (a topical drug, not a drink or supplement). source	2025-02
EFSA (European Union)	Opinion on safety of green tea catechins: infusions prepared the traditional way are in general considered safe at EU intakes; rare liver injury after infusions; high-dose EGCG supplements raised liver enzymes. source	2018-04
EMA / HMPC (European Union)	Has a final EU herbal monograph and assessment report for Camellia sinensis non fermentatum folium (green tea); EMA page lists the therapeutic area as "Fatigue and weakness". source	2014-04-29 (monograph); 2022-09-26 (assessment addendum)
NICHD LactMed (United States)	Notes caffeine-related infant fussiness only at extremely high maternal intake; tea directly to infants can cause anemia; no oral extract data in breastfeeding. source	2006
NHS (United Kingdom)	Pregnancy: no more than 200 mg of caffeine a day; about 75 mg in a cup of black or green tea. source	2026-06-15
US FDA (United States)	Caffeine consumer update: green tea 37 mg per 12 fl oz; 400 mg a day not generally associated with harm in most adults; lists signs of too much caffeine. source	2024-08-28
IARC (WHO) (International)	Very hot beverages probably carcinogenic to humans (Group 2A); temperature, not the drink, appears responsible. source	2016-06-15

When to get medical help

Yellow skin or eyes, dark urine, pale stools, strong tiredness, itching or pain in the upper right belly while using green tea extract: stop it and get medical care now.
Chest pain, a racing or irregular heartbeat, fainting: call emergency services.
Black stools, unusual bruising or bleeding if you take warfarin: contact your prescriber or emergency services.
Very pale skin, breathlessness or marked tiredness in someone who drinks a lot of tea and has low iron: see a clinician.

Stop using the product and contact a clinician or emergency service. In the US, Poison Control is 1-800-222-1222.

General information only, not medical advice. Ask a clinician or pharmacist before use, especially with medicines, in pregnancy or with a health condition. See the Natural Remedy Safety guide.

Frequently asked questions

What is sencha?

Sencha is a Japanese green tea made from the leaves of the tea plant, Camellia sinensis. The fresh leaves are steamed, which keeps them green. Sencha, gyokuro and matcha are all Japanese green teas. The drink contains caffeine, the amino acid theanine and catechins.

^{15 31 41}

Is sencha the same as green tea extract?

No. A cup of tea is a weak water extract. Capsules and tablets are concentrated catechins and have been linked to rare serious liver injury. NCCIH reports no safety concerns for the drink in adults. Do not carry safety or benefit results from one to the other.

^{35 5 9}

Do Japanese people who drink green tea live longer?

In the Ohsaki study of 40,530 adults, heavier green tea drinkers had lower all-cause and cardiovascular death, and pooled data from eight Japanese cohorts showed a similar pattern. These are associations, drinkers may differ in other habits, and NCCIH says the heart link is seen in Asian but not Western groups. Neither study names sencha.

^{16 1 35}

Does it lower cholesterol or blood pressure?

Maybe slightly. A 2011 pooled analysis found small falls in total and LDL cholesterol, and a 2025 review of 36 trials found about 1 mmHg lower blood pressure, with big differences between trials. A 2020 review of short tea trials found no effect, and most trials mix drinks and extracts. Evidence is low.

^{32 26 11 7}

Does it help you lose weight?

Not much. A Cochrane review of 12 to 13 week trials found almost no weight change outside Japan (-0.04 kg on average). Japanese trials varied and could not be pooled.

¹³

Does it prevent cancer?

This has not been shown. A Cochrane review of 142 studies found limited, inconsistent, low-certainty evidence, and the Ohsaki cohort found no lower cancer death in tea drinkers.

^{6 16 35}

Does it help focus, memory or stress?

A review of 21 mostly small studies reported better attention and memory and less anxiety, mainly from caffeine and L-theanine together. One tiny study of 22 young men, with tea company authors, found a higher flow score but no change in accuracy. A lab analysis suggests sencha has a calming ingredient mix, but no people were tested. Certainty is low to very low.

^{19 18 30 14}

Can it hurt the liver?

The drink rarely does. NCCIH reports no safety concerns for the beverage in adults, and liver injury is mostly linked to extract capsules and tablets. EFSA noted rare cases after infusions, likely an individual reaction. LiverTox lists liver failure and transplant for extracts. Stop any extract and get medical care if you notice yellow skin or eyes or dark urine.

^{35 5 22 25 9}

Is it safe in pregnancy, breastfeeding or for children?

Sencha has caffeine, so it counts toward your daily limit. The NHS says to have no more than 200 mg of caffeine a day in pregnancy and counts about 75 mg in a cup of black or green tea. LactMed reports infant fussiness only at extremely high maternal caffeine. Do not give tea to infants, and the FDA quotes guidance to avoid caffeinated drinks for children under 2. No source read covers extract capsules in pregnancy, so ask a clinician.

^{36 21 34 35}

Does it interact with medicines such as warfarin?

NCCIH says high doses of green tea lowered blood levels of nadolol and the extract lowered atorvastatin, and that a study showed an interaction with raloxifene. One 1999 case report links very large amounts of green tea with weaker warfarin effect. Ask your pharmacist or prescriber, and tell them about any big change in tea habits.

^{35 28}

Is there fluoride, aluminium or radioactivity in Japanese tea?

Tea in general contains fluoride and aluminium; studies in Slovenia and Poland found them in infusions, with Polish hazard values below the safety threshold overall but highest in older low-weight women drinking green tea. Health Canada found trace radioactive cesium in Japanese green tea products after the 2011 Fukushima accident and saw no health concern at those levels. Neither the fluoride nor aluminium studies name Japanese teas.

^{24 20 4 23}

Does tea affect iron, and is very hot tea a problem?

Tea polyphenols lowered iron absorption from a meal in a lab study (green tea was not tested), and a 2024 case report links moderate green tea with severe iron-deficiency anemia. IARC classed very hot beverages as probably carcinogenic to the oesophagus; it is the temperature, not the tea, so let a cup cool.

^{10 8 33}

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Editorial transparency

Written by: AlternativeMed editorial team. Research compiled with AI assistance, then checked against PubMed records.
Medical review: None. This page has not been reviewed by a physician or pharmacist.
First published: 2026-10-25
Last substantive update: 2026-10-25
How we research: We searched PubMed and read the abstracts of about 30 sources, read the NCCIH and NHS pages in full, carried over the FDA, EMA and IARC records from our green tea profile, checked the plant name in GBIF, and looked for LiverTox and LactMed (summary records read; the full LiverTox page was not opened). Only abstracts were read for papers. Certainty ratings are the compiler's own reading. Industry links are flagged where we saw them (a tea company in one trial; a supplement company behind one safety review). No study is cited that we could not verify.
How we rate evidence: See "How we rate evidence" in the Evidence tab.
Independence: No product is promoted on this page. No affiliate links are shown. This page is information, not a recommendation to drink or take anything.

Sources 41

Each source was opened and checked. Where we read only the abstract, it says so. The small numbers in the text point here.

Abe SK, Saito E, Sawada N, et al. Green tea consumption and mortality in Japanese men and women: a pooled analysis of eight population-based cohort studies in Japan. European Journal of Epidemiology. 2019. PMID 31392470. DOI 10.1007/s10654-019-00545-y. (abstract)
Acosta L, Byham-Gray L, Kurzer M, et al. Hepatotoxicity with High-Dose Green Tea Extract: Effect of Catechol-O-Methyltransferase and Uridine 5-Diphospho-glucuronosyltransferase 1A4 Genotypes. Journal of Dietary Supplements. 2023. PMID 36178169. DOI 10.1080/19390211.2022.2128501. (abstract)
Asbaghi O, Fouladvand F, Gonzalez MJ, et al. Effect of green tea on glycemic control in patients with type 2 diabetes mellitus: A systematic review and meta-analysis. Diabetes & Metabolic Syndrome. 2021. PMID 33285391. DOI 10.1016/j.dsx.2020.11.004. (abstract)
Cook MC, Stukel MJ, Zhang W, et al. The determination of Fukushima-derived cesium-134 and cesium-137 in Japanese green tea samples and their distribution subsequent to simulated beverage preparation. Journal of Environmental Radioactivity. 2016. PMID 26714059. DOI 10.1016/j.jenvrad.2015.12.010. (abstract)
EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS), Younes M, Aggett P, et al. Scientific opinion on the safety of green tea catechins. EFSA Journal. 2018. PMID 32625874. DOI 10.2903/j.efsa.2018.5239. (abstract)
Filippini T, Malavolti M, Borrelli F, et al. Green tea (Camellia sinensis) for the prevention of cancer. Cochrane Database of Systematic Reviews. 2020. PMID 32118296. DOI 10.1002/14651858.CD005004.pub3. (abstract)
Hartley L, Flowers N, Holmes J, et al. Green and black tea for the primary prevention of cardiovascular disease. Cochrane Database of Systematic Reviews. 2013. PMID 23780706. DOI 10.1002/14651858.CD009934.pub2. (abstract)
He Y, Chen J. Severe iron-deficiency anemia after short-term moderate consumption of green tea in woman: A rare case report. Heliyon. 2024. PMID 39263133. DOI 10.1016/j.heliyon.2024.e36666. (abstract)
Hu J, Webster D, Cao J, et al. The safety of green tea and green tea extract consumption in adults - Results of a systematic review. Regulatory Toxicology and Pharmacology. 2018. PMID 29580974. DOI 10.1016/j.yrtph.2018.03.019. (abstract)
Hurrell RF, Reddy M, Cook JD. Inhibition of non-haem iron absorption in man by polyphenolic-containing beverages. British Journal of Nutrition. 1999. PMID 10999016. (abstract)
Igho-Osagie E, Cara K, Wang D, et al. Short-Term Tea Consumption Is Not Associated with a Reduction in Blood Lipids or Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Journal of Nutrition. 2020. PMID 33188386. DOI 10.1093/jn/nxaa295. (abstract)
Jayasingha H, Amarasooriya G, Rajapaksha N, et al. Fluoride in tea: accumulation, dietary exposure, and future strategies for risk mitigation in food safety; a scoping review. Critical Reviews in Food Science and Nutrition. 2025. PMID 40504749. DOI 10.1080/10408398.2025.2516756. (abstract)
Jurgens TM, Whelan AM, Killian L, et al. Green tea for weight loss and weight maintenance in overweight or obese adults. Cochrane Database of Systematic Reviews. 2012. PMID 23235664. DOI 10.1002/14651858.CD008650.pub2. (abstract)
Kakutani S, Watanabe H, Murayama N. Green Tea Intake and Risks for Dementia, Alzheimer's Disease, Mild Cognitive Impairment, and Cognitive Impairment: A Systematic Review. Nutrients. 2019. PMID 31137655. DOI 10.3390/nu11051165. (abstract)
Kawahara Y, Tanaka J, Takayama K, et al. Chromosome-Scale Genome Assembly and Characterization of Top-Quality Japanese Green Tea Cultivar 'Seimei'. Plant and Cell Physiology. 2024. PMID 38807462. DOI 10.1093/pcp/pcae060. (abstract)
Kuriyama S, Shimazu T, Ohmori K, et al. Green tea consumption and mortality due to cardiovascular disease, cancer, and all causes in Japan: the Ohsaki study. JAMA. 2006. PMID 16968850. DOI 10.1001/jama.296.10.1255. (abstract)
Kuriyama S, Hozawa A, Ohmori K, et al. Green tea consumption and cognitive function: a cross-sectional study from the Tsurugaya Project 1. American Journal of Clinical Nutrition. 2006. PMID 16469995. DOI 10.1093/ajcn/83.2.355. (abstract)
Kurosaka C, Miyake S, Kobayashi M, et al. Green tea consumption rapidly enhances cognitive performance and flow state during mental tasks in healthy young adults. PLoS One. 2025. PMID 40638646. DOI 10.1371/journal.pone.0328394. (abstract)
Mancini E, Beglinger C, Drewe J, et al. Green tea effects on cognition, mood and human brain function: A systematic review. Phytomedicine. 2017. PMID 28899506. DOI 10.1016/j.phymed.2017.07.008. (abstract)
Małyszek A, Zawiślak I, Kulus M, et al. Assessment of Fluoride Intake Risk via Infusions of Commercial Leaf Teas Available in Poland Using the Target Hazard Quotient Index Approach. Foods. 2025. PMID 40941060. DOI 10.3390/foods14172944. (abstract)
NICHD / NLM. Drugs and Lactation Database (LactMed): Green Tea. LactMed (NCBI Bookshelf). 2006. PMID 30000907. (abstract)
NIDDK. LiverTox: Green Tea (Clinical and Research Information on Drug-Induced Liver Injury). LiverTox (NCBI Bookshelf). 2012. PMID 31643260. (abstract)
Nakamura K, Chiba S, Kiuchi T, et al. Comprehensive analysis of a decade of cumulative radiocesium testing data for foodstuffs throughout Japan after the 2011 Fukushima Daiichi Nuclear Power Plant accident. PLoS One. 2022. PMID 36129916. DOI 10.1371/journal.pone.0274070. (abstract)
Pavlovič A, Tavčar G, Ponikvar-Svet M. Fluoride and Aluminium in Tea (Camellia sinensis L.)-Tea Quality Indicators and Risk Factors for Consumers. Molecules. 2023. PMID 37687225. DOI 10.3390/molecules28176396. (abstract)
Pillukat MH, Bester C, Hensel A, et al. Concentrated green tea extract induces severe acute hepatitis in a 63-year-old woman - a case report with pharmaceutical analysis. Journal of Ethnopharmacology. 2014. PMID 24862489. DOI 10.1016/j.jep.2014.05.015. (abstract)
Rezaei M, Akhavan N, Fathi F, et al. Effect of green tea supplementation on blood pressure in adults: a GRADE-assessed systematic review and dose-response meta-analysis of randomised controlled trials. Blood Pressure. 2025. PMID 40497293. DOI 10.1080/08037051.2025.2517122. (abstract)
Rodriguez I, Burgos A, Rubio C, et al. Human exposure to fluoride from tea (Camellia sinensis) in a volcanic region - Canary Islands, Spain. Environmental Science and Pollution Research. 2020. PMID 32740848. DOI 10.1007/s11356-020-10319-9. (abstract)
Taylor JR, Wilt VM. Probable antagonism of warfarin by green tea. Annals of Pharmacotherapy. 1999. PMID 10332534. DOI 10.1345/aph.18238. (abstract)
Tomata Y, Kakizaki M, Nakaya N, et al. Green tea consumption and the risk of incident functional disability in elderly Japanese: the Ohsaki Cohort 2006 Study. American Journal of Clinical Nutrition. 2012. PMID 22277550. DOI 10.3945/ajcn.111.023200. (abstract)
Unno K, Ikka T, Yamashita H, et al. Stress-Relieving Effects of Japanese Green Tea: Evaluation Using the Molar Ratio of Caffeine and Epigallocatechin Gallate to Theanine and Arginine as an Indicator. Foods. 2025. PMID 39796392. DOI 10.3390/foods14010103. (abstract)
Unno K, Kameoka Y, Nakamura Y. Compositional Diversity and Functional Interactions of Bioactive Compounds in Japanese Green Tea: Focus on Matcha, Sencha, and Gyokuro. Molecules. 2026. PMID 42654013. DOI 10.3390/molecules31162934. (abstract)
Zheng XX, Xu YL, Li SH, et al. Green tea intake lowers fasting serum total and LDL cholesterol in adults: a meta-analysis of 14 randomized controlled trials. American Journal of Clinical Nutrition. 2011. PMID 21715508. DOI 10.3945/ajcn.110.010926. (abstract)
n/a. IARC (WHO): Press release no. 244, coffee, mate and very hot beverages (15 June 2016). n/a. 2016. (full-text)
n/a. FDA: Spilling the Beans: How Much Caffeine Is Too Much? (content current as of 28 Aug 2024). n/a. 2024. (full-text)
n/a. NCCIH (NIH): Green Tea: Usefulness and Safety (last updated February 2025). n/a. 2025. (full-text)
n/a. NHS (UK): Foods to avoid in pregnancy (page last reviewed 15 June 2026). n/a. 2026. (full-text)
n/a. EMA: Camelliae sinensis non fermentatum folium (green tea), herbal medicinal product page. n/a. 2026. (abstract)
n/a. PubChem: epigallocatechin gallate (CID 65064), formula C22H18O11. n/a. 2026. (full-text)
n/a. PubChem: caffeine (CID 2519), formula C8H10N4O2. n/a. 2026. (full-text)
n/a. PubChem: L-theanine (CID 439378), formula C7H14N2O3. n/a. 2026. (full-text)
n/a. GBIF Backbone Taxonomy: Camellia sinensis (L.) Kuntze (usage key 3189635), retrieved 2026-10-25. n/a. 2026. (full-text)

Where to buy

Check the label first. Whatever you buy, look for these:

The herb is the first or only ingredient
Organic or lab-tested if that matters to you
Loose leaf or tea bags, and how long they have been stored
If you take medicines or are pregnant, ask a pharmacist about the herb first

Talk to a pharmacist or doctor before you start any supplement, especially if you take medicines. See the Safety tab for interactions.

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Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.