Functional Foods · Drink
Coffee
Coffea arabica; Coffea canephora · also called Brewed coffee, arabica, robusta
Coffee is a drink made from roasted coffee seeds. Plain brewed coffee has almost no calories and about 95 mg of caffeine a cup. Large reviews link about three to four cups a day with lower risk of early death, heart disease and type 2 diabetes, but these are observational links, not proof of cause. The main cautions are sleep, blood pressure, pregnancy, reflux, cholesterol with unfiltered coffee, and some medicines.
General information, not medical advice. Last substantive update · Not medically reviewed. A named clinician has not signed off on this page. How this page is made
About Coffee
Coffee is a drink made from roasted coffee seeds. Plain black coffee has almost no calories, and a cup has about 95 mg of caffeine. It is a drink, not a proven remedy: the long-term findings are observational links, and the main cautions are about caffeine.
What it is
Coffee is made by brewing the roasted seeds of two species, Coffea arabica (arabica) and Coffea canephora (robusta). GBIF lists both as accepted names in the family Rubiaceae. This page is about coffee as a drink. Decaf coffee has its own page, and caffeine pills and green coffee bean extract are different products.
USDA data for brewed coffee made with tap water, per 100 g: 1 kcal, 0.12 g protein, 0.02 g fat, 0 g carbohydrate, 0 g sugars, 49 mg potassium, 3 mg magnesium, 0.076 mg riboflavin and 40 mg caffeine. For a 237 g cup (8 fl oz) that works out to about 2 kcal, 116 mg potassium, 0.18 mg riboflavin and about 95 mg of caffeine. FDA lists 113 to 247 mg of caffeine in 12 fl oz of regular brewed coffee, so cups differ a lot.
What the research shows
Almost all long-term findings are observational: researchers watched what coffee drinkers and non-drinkers did over time. Coffee drinkers can differ from non-drinkers in smoking, diet and other habits, so a link is not proof of cause. An umbrella review of 201 meta-analyses found the lowest risk of all-cause mortality (RR 0.83), cardiovascular mortality (RR 0.81) and cardiovascular disease (RR 0.85) at three to four cups a day versus none. Its authors say robust randomised trials are needed. A cohort meta-analysis found about 13% lower all-cause mortality at 3 cups a day, with similar links for decaf, and a meta-analysis of 28 cohort studies found lower type 2 diabetes risk with more cups (RR 0.67 at 6 cups a day).
Trials point in a more mixed direction. A meta-analysis of 12 trials found coffee raised total cholesterol, LDL and triglycerides, more with unfiltered coffee. A meta-analysis of 10 trials found no significant change in blood pressure, while an umbrella review reports caffeine raises it. A small 8-week trial found no change in blood sugar measures. In 2026 the DECAF trial found less atrial fibrillation recurrence with coffee than with abstinence in 200 people after cardioversion, but it was one open-label trial in a specific group.
Observational studies also link coffee with lower liver cancer risk (OR 0.50 in 16 studies) and, in an umbrella review, with a lower risk of Parkinson's disease. IARC (2016) says coffee drinking is not classifiable as to its cancer risk.
Coffee versus other caffeine products
The findings here are for coffee as a drink. Caffeine pills, energy drinks, green coffee bean extract and decaf coffee are different products, and some reviews (sleep, blood pressure) are about caffeine from several sources. Decaf showed similar links with deaths and diabetes in cohort studies. Milk, sugar, cream and syrups were not studied here; check the label for what they add.
At a glance
Traditional uses history, not proof
- Drunk as a daily drink in many places
- Long use as a drink is not proof that it treats any condition
Studied for research
- Deaths from any cause, low certainty (observational)
- Heart and blood vessel disease, low certainty (observational)
- Type 2 diabetes risk, low certainty (observational; one small trial did not change blood sugar)
- Blood pressure, mixed
- Blood cholesterol, low certainty of a rise, mainly with unfiltered coffee
- Liver cancer risk, low certainty (observational)
- Heart rhythm after cardioversion, low certainty (one trial)
- Sleep, moderate certainty that caffeine disturbs sleep
Main compounds
- Caffeine
- Riboflavin (vitamin B2) in small amounts
- Potassium in small amounts
Common forms
- Plain brewed coffee made with tap water (USDA values read)
- Filtered and unfiltered coffee (compared in cholesterol trials)
- Decaffeinated coffee has its own page
- Espresso, instant, cold brew and coffee with milk, sugar or syrup (nutrient values not read)
- Caffeine pills, powders and green coffee bean extract are different products and are not covered
Research links: 2017 BMJ umbrella review: coffee and health outcomes · 2014 review: coffee and type 2 diabetes (28 studies) · 2026 trial: coffee and atrial fibrillation (DECAF) · Research Library · Genes & Biomarkers Library
What it is and its history
- Accepted scientific name
- Coffea arabica L.; Coffea canephora Pierre ex A.Froehner
- Naming authority
- L. (arabica); Pierre ex A.Froehner (canephora), both ACCEPTED, exact match in GBIF; coffee as a drink is made from the roasted seeds of these two species
- Common names
- Coffee (English); Brewed coffee (English); Arabica (English); Robusta (Coffea canephora) (English); Cafe (Spanish)
- Family or group
- Rubiaceae (the madder or coffee family), as given by GBIF. Coffee as a drink is a processed product: roasted seeds, ground and brewed in water.
- Classification
- Plantae > Tracheophyta > Magnoliopsida > Gentianales > Rubiaceae > Coffea > Coffea arabica; Coffea canephora
- Native range
- Not verified from a source read.
- Habitat
- Not verified from a source read.
- What it looks like
- Roots: Not verified.; Stems: Not verified.; Leaves: Not verified.; Flowers: Not verified.; Fruit: Brewed from roasted seeds; USDA gives household portions of 1 fl oz (29.6 g), 6 fl oz (178 g) and 1 cup of 8 fl oz (237 g).
- Cultivation
- Not verified from a source read.
- Harvest and processing
- Roasting, grinding and brewing details were not read from a source. USDA's item is brewed coffee prepared with tap water.
- Look-alikes and adulterants
- Name: Decaffeinated coffee; Note: Has its own page; FDA says decaf typically has 2 to 15 mg of caffeine in 8 fl oz.; Name: Green coffee bean extract and caffeine supplements; Note: Concentrated products, not the drink, with their own pages.; Name: Tea, cocoa and energy drinks; Note: Other caffeine sources with different compounds and amounts.
- Sustainability and conservation
- Not assessed.
Photographs
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 |
|---|---|---|---|---|
| Caffeine PubChem 2519 | methylxanthine (purine alkaloid) | Seed (roasted) USDA: 40 mg per 100 g brewed coffee (about 95 mg in a 237 g cup); FDA: 113 to 247 mg in 12 fl oz of regular brewed non-specialty coffee | Stimulates the nervous system, raises blood pressure, increases stomach acid release and is a diuretic (MedlinePlus). 21 22 15 19 | Human data |
| Riboflavin (vitamin B2) PubChem 493570 | vitamin | Seed (roasted, brewed) USDA: 0.076 mg per 100 g brewed coffee (about 0.18 mg in a 237 g cup) | A nutrient fact; no trial of coffee for riboflavin status was read. 22 21 | Nutrient database |
| Potassium | mineral | Brewed drink USDA: 49 mg per 100 g (about 116 mg in a 237 g cup) | A nutrient fact. 22 | Nutrient database |
Mechanisms, receptors and pathways
| Target or pathway | Gene or receptor | What was found | Level |
|---|---|---|---|
| Central nervous system stimulation by caffeine | Not specified in the sources read | MedlinePlus says caffeine stimulates the central nervous system, which can make you feel more awake. EFSA says that in moderate doses caffeine increases alertness and reduces sleepiness. 19 14 | Authoritative guidance |
| Stomach acid, diuresis, calcium absorption and blood pressure | Not specified in the sources read | MedlinePlus says caffeine increases stomach acid release, is a diuretic, may interfere with calcium absorption and increases blood pressure. 19 | Authoritative guidance |
Absorption, metabolism and elimination
- Absorption
- MedlinePlus says caffeine reaches its peak level in the blood within one hour of eating or drinking it.
- Distribution
- MedlinePlus says caffeine passes through the placenta and a small amount passes to a breastfed baby.
- Metabolism
- Not found in the sources read, except that FDA and EFSA say people differ widely in how fast they clear caffeine.
- Elimination
- MedlinePlus says effects may continue for four to six hours.
- Bioavailability
- Not established in the sources read.
Isolated compounds versus whole extracts
The findings here are for coffee as a drink. Caffeine pills and powders, energy drinks, green coffee bean extract and decaf coffee are different products. The sleep and blood pressure findings in some reviews are for caffeine from several sources. Decaf coffee showed similar inverse links with deaths and diabetes in cohort studies. Unfiltered coffee raised cholesterol more than filtered coffee in trials.
Nutritional composition
Nutrition from USDA FoodData Central item 171890, brewed coffee prepared with tap water (SR Legacy, April 2018 release), read 2026-10-26 from the saved USDA copy in the project. Per 100 g: 1 kcal, 99.39 g water, 0.12 g protein, 0.02 g fat, 0 g carbohydrate, 0 g sugars, 0 g fibre, 49 mg potassium, 2 mg sodium, 3 mg magnesium, 0.076 mg riboflavin, 0.191 mg niacin and 40 mg caffeine. A 237 g cup (1 cup of 8 fl oz) has about 2 kcal, 116 mg potassium, 0.18 mg riboflavin and about 95 mg of caffeine (simple arithmetic from the per-100 g values). Plain brewed coffee only: espresso, instant, cold brew and coffee with milk, sugar or syrup were not read.
1 high certainty1 moderate certainty1 mixed findings9 low certainty
What was looked at
The 12 benefits and uses checked for Coffee, each with how strong the evidence is. Tap one to open it.
- Deaths from any cause (observational)Low certainty
- Heart and blood vessel disease (observational)Low certainty
- Type 2 diabetes risk (observational)Low certainty
- Blood pressureMixed findings
- Blood cholesterol and fats (a rise, mainly with unfiltered coffee)Low certainty
- Liver cancer risk (observational)Low certainty
- Cancer risk overall (observational)Low certainty
- Parkinson's disease risk (observational)Low certainty
- Heart rhythm after cardioversion (atrial fibrillation)Low certainty
- Acid reflux (GERD) (slightly more reflux in coffee drinkers)Low certainty
- Sleep (caffeine disturbs sleep)Moderate certainty
- What is in a cup (nutrient content)High certainty
Lab markers tracked in the studies
LDL cholesterolTriglyceridesSystolic blood pressureGlucose tolerance and insulin sensitivityTotal sleep timeRecurrence of atrial fibrillation or flutter
What is Coffee good for?
The main studied uses and how strong the human evidence is for each. Most results are observational links for coffee as a drink; the sleep result is for caffeine in general.
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.
Deaths from any cause (observational)
Low certaintyIn large reviews of cohort studies, people who drank about three to four cups of coffee a day had a lower risk of death from any cause than people who drank none. This is a link, not proof that coffee is the cause.
2 studiesBrewed coffee as drunk, caffeinated and decaffeinated, in cohort stud…
Studies, doses and limits
What the trials found
An umbrella review of 201 meta-analyses of observational studies found the lowest risk of all-cause mortality at three to four cups a day versus none (RR 0.83). A separate dose-response meta-analysis of 21 cohort articles (10,103,115 people, 240,303 deaths) found about 13% lower risk at 3 cups a day (RR 0.87), with similar inverse links for caffeinated and decaffeinated coffee.
Results
A consistent lower risk of death in cohort studies, strongest at moderate intakes. Observational studies cannot show that coffee is the cause: coffee drinkers can differ from non-drinkers in smoking, diet and other habits.
Effect sizes as reported
RR 0.83 (95% CI 0.79 to 0.88) at three to four cups a day versus none (umbrella review); RR 0.87 (0.84 to 0.89) at 3 cups a day (cohort meta-analysis).
Why this rating
Low because the evidence is observational and cannot rule out other habits of coffee drinkers. The two reviews agree in direction and are large. No trial tested coffee for longer life.
Form and dose studied
Brewed coffee as drunk, caffeinated and decaffeinated, in cohort studies. Amounts differ between studies.
Who was studied
Adults in many countries; the BMJ review excluded studies of genetic variants for coffee metabolism.
Limits
Links, not cause. The BMJ review's authors say robust randomised trials are needed to know whether the links are causal. Smoking and other habits can mix with the results.
Why researchers looked
Coffee is one of the most widely drunk drinks, so researchers have looked at whether coffee drinkers live longer.
Traditional use
Coffee is drunk daily in many places. Long use as a drink is not proof that it treats any condition.
Proposed mechanism Unknown
Not shown. The reviews measured links between coffee drinking and outcomes, not how coffee might act.
A proposed mechanism does not show that the effect happens in people.
See the Safety tab, especially pregnancy and caffeine.
Heart and blood vessel disease (observational)
Low certaintyIn pooled cohort studies, coffee drinkers had lower risk of cardiovascular disease and cardiovascular death than non-drinkers, with the lowest risk at three to four cups a day. Trials of caffeine show a small rise in blood pressure, so the picture is mixed.
2 studiesBrewed coffee as drunk. Different coffee types were not separated in …
Studies, doses and limits
What the trials found
In the BMJ umbrella review, at three to four cups a day versus none, cardiovascular mortality was lower (RR 0.81) and so was cardiovascular disease (RR 0.85). The Annual Review of Nutrition umbrella review reported a probable decreased risk of cardiovascular disease and mortality in observational studies.
Results
A lower risk in observational data at moderate intakes. Observational studies cannot show that coffee is the cause: coffee drinkers can differ from non-drinkers in smoking, diet and other habits.
Effect sizes as reported
Cardiovascular mortality RR 0.81 (0.72 to 0.90); cardiovascular disease RR 0.85 (0.80 to 0.90), three to four cups a day versus none.
Why this rating
Low: observational. The same reviews report that trials show rises in serum lipids and in blood pressure with caffeine, so short-term trial effects point in a less favourable direction.
Form and dose studied
Brewed coffee as drunk. Different coffee types were not separated in the abstracts.
Who was studied
Adults.
Limits
Observational; trial results on blood pressure and cholesterol are mixed (see those entries).
Why researchers looked
Coffee affects blood pressure and blood fats in the short term, so researchers asked what it does over years.
Traditional use
Coffee is drunk daily in many places. Long use as a drink is not proof that it treats any condition.
Proposed mechanism Unknown
Not shown in these reviews.
A proposed mechanism does not show that the effect happens in people.
People with heart rhythm problems or high blood pressure should ask their clinician.
Type 2 diabetes risk (observational)
Low certaintyMore cups of coffee a day went with a lower risk of developing type 2 diabetes in pooled cohort studies. In an 8-week trial of 5 cups a day, blood sugar measures did not change. Decaf showed a similar link.
2 studiesCohorts: caffeinated and decaffeinated coffee, 1 to 6 cups a day. Tri…
Studies, doses and limits
What the trials found
A meta-analysis of 28 prospective studies (1,109,272 people, 45,335 cases) found RR 0.92, 0.85, 0.79, 0.75, 0.71 and 0.67 for 1 to 6 cups a day versus none. Per extra cup a day, RR was 0.91 for caffeinated and 0.94 for decaffeinated coffee. In a randomised trial of 45 healthy overweight adults, 5 cups a day of instant coffee for 8 weeks gave no significant change in glucose tolerance, insulin sensitivity or insulin secretion.
Results
A dose-response link in cohorts. The one trial did not change glucose measures in 8 weeks.
Effect sizes as reported
Cohorts: RR 0.67 (95% CI 0.61 to 0.74) at 6 cups a day. Trial: no significant difference in glucose measures.
Why this rating
Low: observational for the main finding; the one trial read was tiny (45 people), short, and in healthy people, and did not move blood sugar measures.
Form and dose studied
Cohorts: caffeinated and decaffeinated coffee, 1 to 6 cups a day. Trial: instant coffee, 5 cups a day for 8 weeks.
Who was studied
Adults. The trial enrolled healthy overweight volunteers who were regular coffee drinkers.
Limits
No trial of coffee preventing diabetes was read. The cohorts cannot rule out other habits.
Why researchers looked
Coffee drinkers in cohort studies developed diabetes less often, so researchers asked whether coffee changes blood sugar.
Traditional use
Coffee is drunk daily in many places. Long use as a drink is not proof that it treats any condition.
Proposed mechanism Human data
Not shown. The 8-week trial saw changes in some blood markers (adiponectin, interleukin-6, fetuin-A) but the authors do not claim a proven pathway.
A proposed mechanism does not show that the effect happens in people.
Sugar and cream added to coffee are not covered by these studies.
Blood pressure
Mixed findingsPooled trials of coffee found no significant change in blood pressure. A different umbrella review reports that caffeine raises it. People with high blood pressure should ask their clinician.
3 studiesCoffee as drunk (Steffen); caffeine (Grosso, acute outcomes).
Studies, doses and limits
What the trials found
A meta-analysis of 10 randomised trials found no significant change in systolic (-0.55 mmHg) or diastolic (-0.45 mmHg) blood pressure with more coffee, and 5 cohort studies found no significant link with developing hypertension (RR 1.03). The authors rated the evidence low-quality and made no recommendation for or against coffee. The Annual Review of Nutrition umbrella review reports caffeine linked with a rise in blood pressure in meta-analyses of trials.
Results
Mixed: no significant change for coffee in one meta-analysis; a rise for caffeine in another review.
Effect sizes as reported
Systolic -0.55 mmHg (95% CI -2.46 to 1.36), diastolic -0.45 mmHg (-1.52 to 0.61); hypertension RR 1.03 (0.98 to 1.08).
Why this rating
Mixed: coffee and caffeine trials point in different directions, the coffee meta-analysis is called low quality by its authors.
Form and dose studied
Coffee as drunk (Steffen); caffeine (Grosso, acute outcomes).
Who was studied
Adults.
Limits
Short trials; caffeine and coffee are not the same exposure.
Why researchers looked
Caffeine is known to raise blood pressure for a short time, so researchers asked about long-term coffee drinking.
Traditional use
Coffee is drunk daily in many places. Long use as a drink is not proof that it treats any condition.
Proposed mechanism Authoritative guidance
Caffeine raises blood pressure acutely (MedlinePlus). A lasting effect of coffee was not shown.
A proposed mechanism does not show that the effect happens in people.
See the Safety tab: people with high blood pressure are advised to ask a clinician.
Blood cholesterol and fats (a rise, mainly with unfiltered coffee)
Low certaintyIn trials, drinking coffee for about 45 days raised total cholesterol, LDL ('bad') cholesterol and triglycerides on average. The rise was larger with unfiltered coffee.
2 studiesFiltered and unfiltered coffee, caffeinated and decaffeinated; averag…
Studies, doses and limits
What the trials found
A meta-analysis of 12 randomised trials (1,017 people, Western countries) found that drinking coffee for 45 days on average raised total cholesterol by 8.1 mg/dl, LDL cholesterol by 5.4 mg/dl and triglycerides by 12.6 mg/dl. The rise in total cholesterol was greater with unfiltered and caffeinated coffee, and people with hyperlipidemia were more sensitive. The Annual Review of Nutrition umbrella review also reports a rise in serum lipids, affected by significant heterogeneity.
Results
A small average rise in blood fats in short trials; larger with unfiltered coffee.
Effect sizes as reported
Total cholesterol +8.1 mg/dl (95% CI 4.5 to 11.6); LDL +5.4 mg/dl (1.4 to 9.5); triglycerides +12.6 mg/dl.
Why this rating
Low: randomised trials, but short, only in Western countries, with no formal rating from the authors and noted heterogeneity in the umbrella review.
Form and dose studied
Filtered and unfiltered coffee, caffeinated and decaffeinated; average 45 days.
Who was studied
Adults, including people with high blood fats.
Limits
Short trials. This is an effect in the unfavourable direction, listed here because it is one of the best-tested effects of coffee.
Why researchers looked
Researchers asked whether coffee changes blood fats because they are a heart risk marker.
Traditional use
Coffee is drunk daily in many places. Long use as a drink is not proof that it treats any condition.
Proposed mechanism Unknown
Not described in the abstract read. The authors point to unfiltered coffee as the larger source of the rise.
A proposed mechanism does not show that the effect happens in people.
People with high cholesterol can ask their clinician or dietitian about filtered versus unfiltered coffee.
Liver cancer risk (observational)
Low certaintyIn pooled observational studies, people who drank the most coffee had about half the risk of liver cancer of non-drinkers. IARC also notes reduced liver cancer risk in many studies. This is a link, not a proven protection.
2 studiesCoffee as drunk.
Studies, doses and limits
What the trials found
A meta-analysis of 9 case-control and 7 cohort studies found OR 0.50 for high coffee drinkers versus none or almost never (0.50 in case-control, 0.48 in cohort studies; 0.38 in men; 0.60, not significant, in women). IARC (2016) says reduced risk was seen for cancers of the liver and uterine endometrium.
Results
A consistent inverse link in observational studies, with a small number of studies in the analysis.
Effect sizes as reported
OR 0.50 (95% CI 0.42 to 0.59).
Why this rating
Low: observational, only 16 studies; the authors say more prospective studies are needed. Results differed with and without adjustment for liver disease history.
Form and dose studied
Coffee as drunk.
Who was studied
Adults in Asian and European studies.
Limits
A link, not cause. It does not mean coffee treats liver disease.
Why researchers looked
Coffee has been studied against liver disease in many cohorts.
Traditional use
Coffee is drunk daily in many places. Long use as a drink is not proof that it treats any condition.
Proposed mechanism Unknown
Not shown.
A proposed mechanism does not show that the effect happens in people.
Not a recommendation to drink coffee for the liver.
Cancer risk overall (observational)
Low certaintyHigh versus low coffee drinking went with 18% lower risk of cancer overall in the BMJ umbrella review, and IARC says coffee drinking is not classifiable as a cause of cancer.
3 studiesCoffee as drunk. Very hot drinks are a separate question (see Safety).
Studies, doses and limits
What the trials found
The BMJ umbrella review found high versus low coffee intake went with 18% lower risk of incident cancer (RR 0.82) and a lower risk of several specific cancers. The Annual Review of Nutrition review reports a probable decreased risk of breast, colorectal, colon, endometrial and prostate cancers in observational studies. IARC (2016), after reviewing more than 1000 studies, classified coffee drinking as not classifiable as to carcinogenicity (Group 3), up from its earlier 2B rating, and saw no carcinogenic effect for pancreas, female breast and prostate cancers.
Results
No sign that coffee causes cancer in the reviews read; observational links to lower risk of some cancers.
Effect sizes as reported
Incident cancer RR 0.82 (95% CI 0.74 to 0.89), high versus low.
Why this rating
Low: observational. IARC calls the evidence for a cancer effect inadequate for coffee drinking overall.
Form and dose studied
Coffee as drunk. Very hot drinks are a separate question (see Safety).
Who was studied
Adults.
Limits
Links, not cause; the abstracts do not give separate numbers for each cancer.
Why researchers looked
Coffee was once listed as possibly carcinogenic, so large reviews re-checked the evidence.
Traditional use
Coffee is drunk daily in many places. Long use as a drink is not proof that it treats any condition.
Proposed mechanism Unknown
Not shown.
A proposed mechanism does not show that the effect happens in people.
Very hot drinks and oesophageal cancer: see the Safety tab.
Parkinson's disease risk (observational)
Low certaintyAn umbrella review reports a probable lower risk of Parkinson's disease with coffee, and with caffeine, in observational studies.
1 studiesCoffee and caffeine, as reported in meta-analyses.
Studies, doses and limits
What the trials found
The Annual Review of Nutrition umbrella review reports coffee associated with a probable decreased risk of Parkinson's disease, and caffeine as well, in meta-analyses of observational studies. No numbers are given in the abstract.
Results
A probable lower risk in observational studies, with no numbers read.
Effect sizes as reported
No numbers in the abstract.
Why this rating
Low: observational, and only the umbrella review's abstract was read; no trial was read.
Form and dose studied
Coffee and caffeine, as reported in meta-analyses.
Who was studied
Adults.
Limits
Only the abstract of one umbrella review was read for this; no numbers, no trial. It does not show coffee prevents or treats Parkinson's disease.
Why researchers looked
Observational studies have found fewer cases of Parkinson's disease among coffee drinkers.
Traditional use
Coffee is drunk daily in many places. Long use as a drink is not proof that it treats any condition.
Proposed mechanism Unknown
Not described in the abstract.
A proposed mechanism does not show that the effect happens in people.
None specific.
Heart rhythm after cardioversion (atrial fibrillation)
Low certaintyIn one randomised trial of 200 coffee drinkers with a heart rhythm problem after cardioversion, those who kept drinking coffee had less recurrence than those who stopped coffee and caffeine. It was one trial, and the people knew which group they were in.
1 studiesCaffeinated coffee, about 1 cup a day on average; abstinence group av…
Studies, doses and limits
What the trials found
In the DECAF trial (200 adults, mean age 69, persistent atrial fibrillation or flutter, 5 hospitals), people were randomised to regular caffeinated coffee (about 7 cups a week) or to abstain from coffee and caffeine for 6 months. Recurrence was 47% with coffee and 64% with abstinence (HR 0.61). There was no significant difference in adverse events.
Results
Fewer recurrences with coffee than with abstinence in this one trial.
Effect sizes as reported
HR 0.61 (95% CI 0.42 to 0.89); 47% versus 64% recurrence.
Why this rating
Low: a single trial, open-label, in a very specific group of heart patients. It does not show coffee prevents heart rhythm problems in people without them, and it conflicts with the older common advice.
Form and dose studied
Caffeinated coffee, about 1 cup a day on average; abstinence group avoided all caffeine.
Who was studied
Adults with persistent AF or atrial flutter after cardioversion who already drank coffee.
Limits
One trial; open-label; the author conflicts listed in PubMed are medical device and drug companies, not a coffee company.
Why researchers looked
Many people with atrial fibrillation are told to avoid caffeine, but this had not been tested in a trial.
Traditional use
Coffee is drunk daily in many places. Long use as a drink is not proof that it treats any condition.
Proposed mechanism Unknown
Not shown.
A proposed mechanism does not show that the effect happens in people.
People with heart rhythm problems should follow their cardiologist's advice.
Acid reflux (GERD) (slightly more reflux in coffee drinkers)
Low certaintyIn a 2026 meta-analysis, acid reflux was slightly more common in coffee drinkers than non-drinkers. There was no link with Barrett's esophagus. The authors say the practical meaning is unclear.
2 studiesCoffee use versus non-use.
Studies, doses and limits
What the trials found
A meta-analysis of 40 studies (122,074 people) found GERD in 34.9% of coffee users and 30.7% of non-users (OR 1.18). There was no significant link with Barrett's esophagus (OR 1.13). The differences between studies were very high (I2 about 89%).
Results
A small link with more reflux; clinical meaning unclear.
Effect sizes as reported
GERD OR 1.18 (95% CI 1.03 to 1.36); Barrett's esophagus OR 1.13 (0.79 to 1.61).
Why this rating
Low: observational with very high differences between studies. The authors call the size of the effect of unclear clinical significance.
Form and dose studied
Coffee use versus non-use.
Who was studied
Adults.
Limits
Observational; coffee drinkers and non-drinkers may differ in other ways.
Why researchers looked
People with reflux are often told to cut back on coffee, but earlier studies disagreed.
Traditional use
Coffee is drunk daily in many places. Long use as a drink is not proof that it treats any condition.
Proposed mechanism Authoritative guidance
MedlinePlus says caffeine increases the release of acid in the stomach, sometimes causing an upset stomach or heartburn.
A proposed mechanism does not show that the effect happens in people.
People with reflux or ulcers are advised by MedlinePlus to ask a clinician about caffeine.
Sleep (caffeine disturbs sleep)
Moderate certaintyA pooled analysis of 24 studies found caffeine reduced total sleep time by about 45 minutes, and made it take longer to fall asleep and easier to wake at night. Most studies were of caffeine in general, not coffee alone.
3 studiesCaffeine of several kinds; a coffee of 107 mg per 250 mL was used in …
Studies, doses and limits
What the trials found
Across 24 studies, caffeine reduced total sleep time by 45 min and sleep efficiency by 7%, increased time to fall asleep by 9 min and waking after sleep onset by 12 min, and reduced deep sleep by 11.4 min. EFSA says single 100 mg doses may affect sleep duration and patterns in some adults, particularly close to bedtime.
Results
Caffeine worsens night-time sleep measures. Timing matters.
Effect sizes as reported
Total sleep time -45 min; sleep efficiency -7%; sleep onset +9 min; waking +12 min; deep sleep -11.4 min.
Why this rating
Moderate: a meta-analysis of 24 studies with clear effects; the abstract gives no confidence intervals and covers caffeine from several sources (including pre-workout products), so it is indirect for a cup of coffee.
Form and dose studied
Caffeine of several kinds; a coffee of 107 mg per 250 mL was used in the authors' timing estimate.
Who was studied
Mostly adults.
Limits
Mixed caffeine sources; individual sensitivity varies.
Why researchers looked
Caffeine blocks tiredness, so researchers measured what it does to sleep.
Traditional use
Coffee is drunk daily in many places. Long use as a drink is not proof that it treats any condition.
Proposed mechanism Authoritative guidance
Caffeine stimulates the central nervous system (MedlinePlus).
A proposed mechanism does not show that the effect happens in people.
See the Safety tab on caffeine.
What is in a cup (nutrient content)
High certaintyBlack brewed coffee has about 2 calories per cup and almost no fat, sugar or protein. A cup has a little potassium and riboflavin, and about 95 mg of caffeine.
3 studiesPlain brewed coffee from USDA tables. Espresso, instant, cold brew, a…
Studies, doses and limits
What the trials found
USDA lists brewed coffee (prepared with tap water) at 1 kcal, 0.12 g protein, 0.02 g fat, 0 g carbohydrate, 0 g sugars, 49 mg potassium, 3 mg magnesium, 0.076 mg riboflavin and 40 mg caffeine per 100 g. For a 237 g cup that is about 2 kcal, 116 mg potassium, 0.18 mg riboflavin and about 95 mg caffeine. FDA lists 113 to 247 mg caffeine in 12 fluid ounces of regular brewed non-specialty coffee, and MedlinePlus lists 95 to 200 mg in 8 ounces.
Results
A nearly calorie-free drink with caffeine; small amounts of a few nutrients.
Effect sizes as reported
Per 237 g cup: about 2 kcal; 116 mg potassium; 0.18 mg riboflavin; about 95 mg caffeine (USDA, arithmetic from per-100 g values).
Why this rating
High that the drink contains these amounts (USDA data for plain brewed coffee). The amounts are small, and caffeine varies widely by brew and cup size.
Form and dose studied
Plain brewed coffee from USDA tables. Espresso, instant, cold brew, and coffee with milk, sugar or syrup were not read.
Who was studied
General diet.
Limits
A nutrient fact, not a health trial. Added milk, sugar, cream and syrups change calories, sugar and fat.
Why researchers looked
People often ask whether plain coffee counts for nutrients.
Traditional use
Coffee is drunk daily in many places. Long use as a drink is not proof that it treats any condition.
Proposed mechanism Nutrient database
These are nutrient amounts in the drink, from USDA tables.
A proposed mechanism does not show that the effect happens in people.
See the Safety tab for caffeine.
Connections to the rest of health
How Coffee 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
A. Wellness goals
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Longevity | Low certainty | Deaths from any cause (observational): In large reviews of cohort studies, people who drank about three to four cups of coffee a day had a lower risk of death from any cause than people who drank none. This is a link, not proof that coffee is the cause. | 8 6 | |
| Healthy Aging | Low certainty | Deaths from any cause (observational): In large reviews of cohort studies, people who drank about three to four cups of coffee a day had a lower risk of death from any cause than people who drank none. This is a link, not proof that coffee is the cause. | 8 6 | |
| Heart Health | Low certainty | Heart and blood vessel disease (observational): In pooled cohort studies, coffee drinkers had lower risk of cardiovascular disease and cardiovascular death than non-drinkers, with the lowest risk at three to four cups a day. Trials of caffeine show a small rise in blood pressure, so the picture is mixed. | 8 5 | |
| Blood Sugar Balance | Low certainty | Type 2 diabetes risk (observational): More cups of coffee a day went with a lower risk of developing type 2 diabetes in pooled cohort studies. In an 8-week trial of 5 cups a day, blood sugar measures did not change. Decaf showed a similar link. | 3 11 | |
| Blood Pressure Support | Mixed findings | Blood pressure: Pooled trials of coffee found no significant change in blood pressure. A different umbrella review reports that caffeine raises it. People with high blood pressure should ask their clinician. | 10 5 19 | |
| Cholesterol Balance | Adverse effect or risk | Low certainty | Blood cholesterol and fats (a rise, mainly with unfiltered coffee): In trials, drinking coffee for about 45 days raised total cholesterol, LDL ('bad') cholesterol and triglycerides on average. The rise was larger with unfiltered coffee. | 2 5 |
| Heart Health | Adverse effect or risk | Low certainty | Blood cholesterol and fats (a rise, mainly with unfiltered coffee): In trials, drinking coffee for about 45 days raised total cholesterol, LDL ('bad') cholesterol and triglycerides on average. The rise was larger with unfiltered coffee. | 2 5 |
| Liver Support | Low certainty | Liver cancer risk (observational): In pooled observational studies, people who drank the most coffee had about half the risk of liver cancer of non-drinkers. IARC also notes reduced liver cancer risk in many studies. This is a link, not a proven protection. | 9 18 | |
| Cellular Protection | Low certainty | Cancer risk overall (observational): High versus low coffee drinking went with 18% lower risk of cancer overall in the BMJ umbrella review, and IARC says coffee drinking is not classifiable as a cause of cancer. | 8 5 18 | |
| Preventive Wellness | Low certainty | Cancer risk overall (observational): High versus low coffee drinking went with 18% lower risk of cancer overall in the BMJ umbrella review, and IARC says coffee drinking is not classifiable as a cause of cancer. | 8 5 18 | |
| Brain Health | Low certainty | Parkinson's disease risk (observational): An umbrella review reports a probable lower risk of Parkinson's disease with coffee, and with caffeine, in observational studies. | 5 | |
| Heart Health | Low certainty | Heart rhythm after cardioversion (atrial fibrillation): In one randomised trial of 200 coffee drinkers with a heart rhythm problem after cardioversion, those who kept drinking coffee had less recurrence than those who stopped coffee and caffeine. It was one trial, and the people knew which group they were in. | 12 | |
| Digestive Health | Adverse effect or risk | Low certainty | Acid reflux (GERD) (slightly more reflux in coffee drinkers): In a 2026 meta-analysis, acid reflux was slightly more common in coffee drinkers than non-drinkers. There was no link with Barrett's esophagus. The authors say the practical meaning is unclear. | 7 19 |
| Sleep Quality | Adverse effect or risk | Moderate certainty | Sleep (caffeine disturbs sleep): A pooled analysis of 24 studies found caffeine reduced total sleep time by about 45 minutes, and made it take longer to fall asleep and easier to wake at night. Most studies were of caffeine in general, not coffee alone. | 4 14 19 |
| Better Sleep | Adverse effect or risk | Moderate certainty | Sleep (caffeine disturbs sleep): A pooled analysis of 24 studies found caffeine reduced total sleep time by about 45 minutes, and made it take longer to fall asleep and easier to wake at night. Most studies were of caffeine in general, not coffee alone. | 4 14 19 |
| Balanced Nutrition | High certainty | What is in a cup (nutrient content): Black brewed coffee has about 2 calories per cup and almost no fat, sugar or protein. A cup has a little potassium and riboflavin, and about 95 mg of caffeine. | 22 15 19 |
B. Body systems
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Whole Body | Biological association | Low certainty | Studied for: Deaths from any cause (observational) | 8 6 |
| Cardiovascular System | Biological association | Low certainty | Studied for: Heart and blood vessel disease (observational) Studied for: Blood pressure | 8 5 10 19 2 12 |
| Blood Sugar Support | Biological association | Low certainty | Studied for: Type 2 diabetes risk (observational) | 3 11 |
| Hepatic System | Biological association | Low certainty | Studied for: Liver cancer risk (observational) | 9 18 |
| Cellular | Biological association | Low certainty | Studied for: Cancer risk overall (observational) | 8 5 18 |
| Nervous System | Biological association | Low certainty | Studied for: Parkinson's disease risk (observational) | 5 |
| Digestive System | Biological association | Low certainty | Studied for: Acid reflux (GERD) (slightly more reflux in coffee drinkers) | 7 19 |
| Sleep Recovery | Biological association | Moderate certainty | Studied for: Sleep (caffeine disturbs sleep) | 4 14 19 |
| Nutrition | Biological association | High certainty | Studied for: What is in a cup (nutrient content) | 22 15 19 |
E. Health conditions
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Poor sleep | Adverse effect or risk | Documented risk | A pooled analysis of 24 studies found caffeine reduced total sleep time by about 45 minutes. Preparation or compound: Caffeine in coffee |
4 14 |
| High blood pressure | Adverse effect or risk | Preliminary or mixed | An umbrella review reports a rise in blood pressure with caffeine in trials; a coffee-only meta-analysis found no significant change. Preparation or compound: Caffeine in coffee |
5 10 |
| Acid reflux (GERD) | Adverse effect or risk | Preliminary or mixed | GERD was slightly more common in coffee users (OR 1.18); clinical meaning unclear. Preparation or compound: Coffee as drunk |
7 |
| Type 2 diabetes | Preliminary or mixed | More cups a day went with lower diabetes risk in 28 cohort studies; one small 8-week trial found no change in glucose measures. Preparation or compound: Coffee as drunk |
3 11 | |
| High cholesterol | Adverse effect or risk | Documented risk | Coffee raised total and LDL cholesterol in trials, more with unfiltered coffee. Preparation or compound: Unfiltered coffee |
2 |
| Atrial fibrillation | Preliminary | One open-label trial found less recurrence with coffee than abstinence after cardioversion. Preparation or compound: Caffeinated coffee |
12 |
I. Biomarkers
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| LDL cholesterol | Biological association | Low certainty | Measured in trials: raised. A lab change is not the same as a health benefit. | 2 |
| Triglycerides | Biological association | Low certainty | Measured in trials: raised. A lab change is not the same as a health benefit. | 2 |
| Systolic blood pressure | Biological association | Mixed findings | Measured in trials: no significant change. A lab change is not the same as a health benefit. | 10 5 |
| Glucose tolerance and insulin sensitivity | Biological association | Low certainty | Measured in trials: no significant change. A lab change is not the same as a health benefit. | 11 |
| Total sleep time | Biological association | Moderate certainty | Measured in trials: lowered. A lab change is not the same as a health benefit. | 4 |
| Recurrence of atrial fibrillation or flutter | Biological association | Low certainty | Measured in trials: lowered. A lab change is not the same as a health benefit. | 12 |
K. Biological pathways
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Caffeine | Preliminary mechanism | Authoritative guidance | The main active compound; official limits (FDA, EFSA, NHS) are set on caffeine. | 15 14 21 |
| Riboflavin | Preliminary mechanism | Nutrient database | Plain brewed coffee has a small amount of riboflavin. | 22 |
L. Active compounds
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Caffeine | Biological association | Human | Stimulates the nervous system, raises blood pressure, increases stomach acid release and is a diuretic (MedlinePlus). Preparation or compound: Seed (roasted) |
21 22 15 19 |
| Riboflavin (vitamin B2) | Biological association | Nutrient database | A nutrient fact; no trial of coffee for riboflavin status was read. Preparation or compound: Seed (roasted, brewed) |
22 21 |
| Potassium | Biological association | Nutrient database | A nutrient fact. Preparation or compound: Brewed drink |
22 |
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 26, 2026).
The evidence
The research centre for Coffee. Every record here was checked against PubMed or the publisher's page; we never list a study we have not verified.
Evidence by outcome
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 started from our existing coffee summary, re-checked nutrition against saved USDA FoodData Central data, read the agency pages (FDA, EFSA, NHS, ACOG, MedlinePlus, IARC press release) and re-read PubMed abstracts for reviews, trials and cohort analyses. Only abstracts were read for studies. Items we could not verify are flagged in the research gaps.
Study library: every study we checked 22
| Study | Design | People | Product, dose, length | Result |
|---|---|---|---|---|
| Brito Nunes 2023 Mendelian randomization study of maternal coffee consumption and its influence on birthweight, stillbirth, miscarriage, gestational age and pre-term birth. Int J Epidemiol · PMID 35679582 · DOI |
Mendelian randomization human (genetic data) |
Genetic data on coffee consumption (N = 91,462) linked to pregnancy outcome data; the one-sample analysis used up to 194,196 UK Biobank women and up to 6,845 mothers in a UK birth cohort | Coffee (genetic liability to drink more coffee) |
Both analyses showed no change in the risk of sporadic miscarriage, stillbirth or pre-term birth, and no effect on gestational age, connected to coffee consumption. Both showed an association between more coffee and higher birthweight, but the size of the effect was inconsistent. The authors suggest coffee in pregnancy might not itself cause stillbirth, sporadic miscarriage, pre-term birth, shorter gestation or lower birthweight. No change in risk (numbers not given in the abstract) (Not given in the abstract) Methods, limits and fundingOutcomes: Miscarriage, stillbirth, pre-term birth, gestational age, birthweight Limitations: A genetic method, not a trial of drinking coffee; it rests on assumptions about the genetic markers, and the authors say randomised trial data are lacking. Funding and conflicts: Funding and competing interests are not given in the abstract. Read: abstract |
| Cai 2012 The effect of coffee consumption on serum lipids: a meta-analysis of randomized controlled trials. Eur J Clin Nutr · PMID 22713771 · DOI |
Systematic review meta analysis |
1017 12 randomised trials from Western countries with 1,017 people |
Coffee (filtered and unfiltered, caffeinated and decaffeinated) Coffee drink Varied by study; a dose-response link was found On average 45 days · vs Control without coffee |
Drinking coffee for 45 days on average was linked with increases of 8.1 mg/dl in total cholesterol, 5.4 mg/dl in LDL cholesterol and 12.6 mg/dl in triglycerides. The total cholesterol rise was greater in trials of unfiltered coffee and caffeinated coffee. People with hyperlipidemia were more sensitive. The authors found a positive dose-response link. Total cholesterol +8.1 mg/dl; LDL +5.4 mg/dl; triglycerides +12.6 mg/dl (Total cholesterol 4.5 to 11.6; LDL 1.4 to 9.5; triglycerides as printed in the abstract '3.5, 12.6' (upper bound looks like a typo)) Methods, limits and fundingOutcomes: Total cholesterol, LDL cholesterol, triglycerides Limitations: Short trials in Western countries only; mixed coffee types; the triglyceride interval is printed oddly in the abstract. Funding and conflicts: Funding and competing interests are not given in the abstract. Read: abstract |
| Ding 2014 Caffeinated and decaffeinated coffee consumption and risk of type 2 diabetes: a systematic review and a dose-response meta-analysis. Diabetes Care · PMID 24459154 · DOI |
Systematic review meta analysis |
1109272 28 prospective studies, 1,109,272 participants, 45,335 cases of type 2 diabetes; follow-up 10 months to 20 years |
Coffee, caffeinated and decaffeinated Coffee drink 1 to 6 cups a day compared with no or rare coffee Follow-up 10 months to 20 years · vs No or rare coffee |
More coffee went with lower diabetes risk in a dose-response way. Compared with no or rare coffee, RR was 0.92, 0.85, 0.79, 0.75, 0.71 and 0.67 for 1, 2, 3, 4, 5 and 6 cups a day. For each extra cup a day, RR was 0.91 for caffeinated coffee and 0.94 for decaffeinated coffee (P for difference = 0.17). RR 0.92 (1 cup) to 0.67 (6 cups) a day; per extra cup: caffeinated 0.91, decaffeinated 0.94 (1 cup 0.90 to 0.94; 6 cups 0.61 to 0.74; caffeinated per cup 0.89 to 0.94; decaffeinated per cup 0.91 to 0.98) Methods, limits and fundingOutcomes: Risk of type 2 diabetes Limitations: Observational (prospective cohort) studies: a link, not proof that coffee prevents diabetes. Funding and conflicts: The abstract record lists NIH extramural research support; no coffee industry funding is stated. Read: abstract |
| Gardiner 2023 The effect of caffeine on subsequent sleep: A systematic review and meta-analysis. Sleep Med Rev · PMID 36870101 · DOI |
Systematic review meta analysis |
24 studies of caffeine and night-time sleep | Caffeine (coffee and other sources, including pre-workout supplements) Caffeine Varied by study; a coffee of 107 mg per 250 mL was used in the authors' timing estimate · vs No caffeine |
Caffeine reduced total sleep time by 45 minutes and sleep efficiency by 7%, and increased the time to fall asleep by 9 minutes and waking after sleep onset by 12 minutes. Light sleep (N1) increased and deep sleep (N3 and N4) decreased by 11.4 minutes. The authors give caffeine timing estimates before bedtime. Total sleep time -45 min; sleep efficiency -7%; sleep onset +9 min; waking after sleep onset +12 min; deep sleep -11.4 min (Not given in the abstract) Methods, limits and fundingOutcomes: Total sleep time, sleep efficiency, time to fall asleep, waking after sleep onset, sleep stages Limitations: Covers caffeine from several sources, not only coffee. Confidence intervals are not given in the abstract. Funding and conflicts: Authors declare no conflicts of interest. Read: abstract |
| Grosso 2017 Coffee, Caffeine, and Health Outcomes: An Umbrella Review. Annu Rev Nutr · PMID 28826374 · DOI |
Umbrella review |
112 meta-analyses of observational studies (59 outcomes) of coffee, 20 of caffeine (14 outcomes), and 9 meta-analyses of randomised trials (12 acute outcomes) | Coffee and caffeine Coffee drink and caffeine Not given in the abstract · vs Little or no coffee, or caffeine |
In observational studies, coffee was linked with a probable decreased risk of breast, colorectal, colon, endometrial and prostate cancers, cardiovascular disease and mortality, Parkinson's disease and type 2 diabetes. Caffeine was linked with a probable decreased risk of Parkinson's disease and type 2 diabetes and an increased risk of pregnancy loss. In the meta-analyses of randomised trials, coffee was linked with a rise in serum lipids (affected by significant heterogeneity) and caffeine with a rise in blood pressure. The authors conclude coffee can be part of a healthful diet. No numbers in the abstract (Not given in the abstract) Methods, limits and fundingOutcomes: Cancers, cardiovascular disease and mortality, Parkinson's disease, type 2 diabetes, pregnancy loss, serum lipids, blood pressure Limitations: Mostly observational. The trial findings are short-term acute outcomes. The abstract gives no numbers and no funding statement. Funding and conflicts: Funding and competing interests are not given in the abstract. Read: abstract |
| Li 2019 Caffeinated and decaffeinated coffee consumption and risk of all-cause mortality: a dose-response meta-analysis of cohort studies. J Hum Nutr Diet · PMID 30786114 · DOI |
Systematic review meta analysis |
10103115 21 cohort study articles with 10,103,115 participants and 240,303 deaths |
Coffee, caffeinated and decaffeinated Coffee drink At 3 cups a day versus no or rare coffee · vs No or rare coffee |
A non-linear link between coffee and all-cause mortality. At 3 cups a day, compared with no or rare coffee, the risk of death from any cause might be 13% lower (RR 0.87). The authors report similar inverse links for caffeinated and decaffeinated coffee. RR 0.87 at 3 cups a day (0.84 to 0.89) Methods, limits and fundingOutcomes: All-cause mortality Limitations: Cohort studies only, so the link may reflect other habits of coffee drinkers; the abstract does not give separate numbers for caffeinated and decaffeinated coffee. Funding and conflicts: Funding and competing interests are not given in the abstract. Read: abstract |
| Muftah 2026 Association of Coffee Intake With Risk of Gastroesophageal Reflux Disease and Complications: A Systematic Review and Meta-Analysis. Clin Transl Gastroenterol · PMID 41677121 · DOI |
Systematic review meta analysis |
122074 40 studies with 122,074 people (85,400 coffee drinkers and 36,674 non-drinkers) |
Coffee (use versus non-use) Coffee drink Coffee drinkers versus non-drinkers · vs Non-drinkers |
GERD was more common among coffee users than non-users (34.9% versus 30.7%; OR 1.18; I2 = 89.38%). There was no significant link between coffee and Barrett's esophagus (OR 1.13). No sign of publication bias. The authors call the size of the effect of unclear clinical significance and say routine coffee avoidance for GERD needs further evaluation. GERD OR 1.18; Barrett's esophagus OR 1.13 (not significant) (GERD 1.03 to 1.36; Barrett's esophagus 0.79 to 1.61) Methods, limits and fundingOutcomes: Gastroesophageal reflux disease (GERD) and Barrett's esophagus Limitations: Observational studies with very high differences between studies (I2 about 89% for GERD). Funding and conflicts: Authors report no competing interests; one author is supported by an NIH/NIDDK training award. Read: abstract |
| Poole 2017 Coffee consumption and health: umbrella review of meta-analyses of multiple health outcomes. BMJ · PMID 29167102 · DOI |
Umbrella review |
Adults in 201 meta-analyses of observational studies (67 outcomes) and 17 meta-analyses of interventional studies (9 outcomes) | Coffee (all types, as drunk) Coffee drink High versus low, any versus none, and one extra cup a day; the lowest risk was at three to four cups a day versus none · vs Little or no coffee |
Coffee was more often linked with benefit than harm. At three to four cups a day versus none the lowest risks were: all-cause mortality RR 0.83, cardiovascular mortality RR 0.81, cardiovascular disease RR 0.85. High versus low intake went with 18% lower risk of incident cancer (RR 0.82). Harmful associations were largely cancelled out by adjusting for smoking, except in pregnancy: high versus low or no intake went with low birth weight (OR 1.31), preterm birth in the first (OR 1.22) and second (OR 1.12) trimester, and pregnancy loss (OR 1.46). There was also an association between coffee and fracture in women but not in men (direction not given in the abstract). All-cause mortality RR 0.83; cardiovascular mortality RR 0.81; cardiovascular disease RR 0.85; incident cancer RR 0.82 (high vs low); pregnancy loss OR 1.46 (All-cause mortality 0.79 to 0.88; cardiovascular mortality 0.72 to 0.90; cardiovascular disease 0.80 to 0.90; cancer 0.74 to 0.89; low birth weight 1.03 to 1.67; first-trimester preterm 1.00 to 1.49; second-trimester preterm 1.02 to 1.22; pregnancy loss 1.06 to 1.99) Methods, limits and fundingOutcomes: All-cause mortality, cardiovascular disease, cancer, neurological, metabolic and liver conditions, pregnancy outcomes, fracture Limitations: Most included meta-analyses were of observational studies, so the results show links, not cause; the authors say robust randomised trials are needed. An erratum was published in 2018 (BMJ 360:k194); only the abstract text was read here. Funding and conflicts: Authors report no support from any organisation for the submitted work; several report pharmaceutical company fees outside the work. No coffee industry funding is declared in the abstract record. Read: abstract |
| Sang 2013 Consumption of coffee associated with reduced risk of liver cancer: a meta-analysis. BMC Gastroenterol · PMID 23433483 · DOI |
Systematic review meta analysis |
9 case-control studies and 7 cohort studies (searched up to May 2012) | Coffee Coffee drink High versus no or almost never drinkers · vs No or almost never drinkers |
The summary odds ratio for high versus no or almost never coffee drinkers was 0.50. It was 0.50 for case-control studies and 0.48 for cohort studies, 0.38 in men and 0.60 in women (not significant in women). The authors suggest an inverse association and say, because of the small number of studies, further prospective studies are needed. OR 0.50 (high vs none) (0.42 to 0.59 overall; men 0.25 to 0.56; women 0.33 to 1.10) Methods, limits and fundingOutcomes: Liver cancer Limitations: Observational; only 16 studies; results differed with and without adjustment for a history of liver disease (OR 0.39 versus 0.54), so people with liver disease may change how much coffee they drink. Funding and conflicts: Funding and competing interests are not given in the abstract (PubMed lists non-US government research support). Read: abstract |
| Steffen 2012 The effect of coffee consumption on blood pressure and the development of hypertension: a systematic review and meta-analysis. J Hypertens · PMID 23032138 · DOI |
Systematic review meta analysis |
15 studies: 10 randomised trials and 5 cohort studies, each at least 1 week long | Coffee Coffee drink More coffee versus less or none At least 1 week · vs Less or no coffee |
In the randomised trials, the pooled change was -0.55 mmHg for systolic and -0.45 mmHg for diastolic blood pressure, neither significant. In the cohort studies, the pooled risk ratio for developing hypertension was 1.03 (not significant). The authors call the evidence low quality, show no significant effect of coffee on blood pressure or hypertension, and say no recommendation can be made for or against coffee. Systolic -0.55 mmHg; diastolic -0.45 mmHg; hypertension RR 1.03 (all not significant) (Systolic -2.46 to 1.36; diastolic -1.52 to 0.61; hypertension 0.98 to 1.08) Methods, limits and fundingOutcomes: Blood pressure and development of hypertension Limitations: Low-quality evidence; short trials; the question of caffeine-only and acute effects is different. Funding and conflicts: Funding and competing interests are not given in the abstract. Read: abstract |
| Wedick 2011 Effects of caffeinated and decaffeinated coffee on biological risk factors for type 2 diabetes: a randomized controlled trial. Nutr J · PMID 21914162 · DOI |
Randomised controlled trial |
45 45 healthy overweight volunteers, average age 40, average BMI 29.5, non-smokers and regular coffee drinkers |
Instant coffee, caffeinated or decaffeinated Coffee drink 5 cups (177 mL each) a day 8 weeks · vs No coffee (water) |
Compared with no coffee, caffeinated coffee increased adiponectin (difference in change 1.4 ug/mL) and interleukin-6 (difference 60%), and decaffeinated coffee decreased fetuin-A (difference -20%). For glucose tolerance, insulin sensitivity and insulin secretion, no significant differences were found between groups. Adiponectin +1.4 ug/mL (caffeinated); interleukin-6 +60% (caffeinated); fetuin-A -20% (decaffeinated); no difference in glucose measures (Adiponectin 0.2 to 2.7; interleukin-6 8 to 138%; fetuin-A -35 to -1%) Methods, limits and fundingOutcomes: Glucose tolerance, insulin sensitivity, insulin secretion, adiponectin, interleukin-6, fetuin-A Limitations: Very small (45 people), 8 weeks, instant coffee, healthy overweight adults; the authors' benefit reading rests on marker changes, not on diabetes outcomes. Funding and conflicts: PubMed lists NIH and non-US government research support; competing interests are not given in the abstract. Registration: NCT00305097 Read: abstract |
| Wong 2026 Caffeinated Coffee Consumption or Abstinence to Reduce Atrial Fibrillation: The DECAF Randomized Clinical Trial. JAMA · PMID 41206802 · DOI |
Randomised controlled trial |
200 200 coffee-drinking adults (mean age 69, 71% male) with persistent atrial fibrillation (AF), or atrial flutter with a history of AF, planned for electrical cardioversion, at 5 hospitals in the US, Canada and Australia |
Caffeinated coffee Coffee drink At least 1 cup a day encouraged; actual intake 7 cups a week (IQR 6 to 11) 6 months · vs Abstain from coffee and caffeine (0 cups a week, IQR 0 to 2) |
Recurrence was lower with coffee (47%) than with abstinence (64%), a 39% lower hazard (HR 0.61; P = .01). The benefit was comparable for AF recurrence alone. There was no significant difference in adverse events. HR 0.61 for recurrence (0.42 to 0.89) Methods, limits and fundingOutcomes: Recurrence of AF or atrial flutter over 6 months Limitations: Open-label (people knew their group), 200 people, in a very specific group of heart patients after cardioversion; one trial. It does not show that coffee prevents heart rhythm problems in people without them. Funding and conflicts: Authors list research and consulting funding from medical device and drug companies; none is from a coffee company in the abstract record. Trial funding is not stated in the abstract. Registration: NCT05121519 Read: abstract |
| s-acog-462 ACOG Committee Opinion 462: Moderate Caffeine Consumption During Pregnancy · Source |
Professional guideline n/a |
Methods, limits and fundingRead: full-text | ||
| s-efsa-caffeine EFSA: Caffeine (Scientific Opinion on the safety of caffeine, published 27 May 2015) · Source |
Regulator n/a |
Methods, limits and fundingRead: full-text | ||
| s-fda-caffeine US FDA: Spilling the Beans: How Much Caffeine is Too Much? · Source |
Health agency n/a |
Methods, limits and fundingRead: full-text | ||
| s-gbif-coffea-arabica GBIF Backbone: Coffea arabica L. (usageKey 2895345) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-gbif-coffea-canephora GBIF Backbone: Coffea canephora Pierre ex A.Froehner (usageKey 2895528) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-iarc-pr244 IARC press release no. 244: IARC Monographs evaluate drinking coffee, mate, and very hot beverages (15 June 2016) · Source |
Regulator n/a |
Methods, limits and fundingRead: full-text | ||
| s-medlineplus-caffeine MedlinePlus (US National Library of Medicine): Caffeine · Source |
Health agency n/a |
Methods, limits and fundingRead: full-text | ||
| s-nhs-foods-pregnancy NHS (UK): Foods to avoid in pregnancy · Source |
Health agency n/a |
Methods, limits and fundingRead: full-text | ||
| s-pubchem-caffeine PubChem: caffeine (CID 2519) and riboflavin (CID 493570) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-usda-fdc-171890 USDA FoodData Central 171890: Beverages, coffee, brewed, prepared with tap water (SR Legacy, April 2018) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text |
What we do not know yet
- No trial tested adding coffee for longer life, fewer heart attacks, fewer cancers or lower diabetes risk; those findings are observational.
- The cholesterol trials were short and Western, and the blood pressure trial analysis is rated low quality by its authors.
- The atrial fibrillation finding comes from one open-label trial and has not been repeated in the sources read.
- No source read named specific medicines that interact with caffeine; acrylamide, mould toxins and pesticide residues, coffee allergy, kidney disease and iron absorption were not researched.
- Espresso, instant, cold brew and coffee with milk or sugar nutrient values, and the history and growing of coffee, were not read.
How new research is added
New studies are found by a saved PubMed search and placed in a review queue before the page changes.
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 2
LDL cholesterol
Raised in trials
The 'bad' cholesterol carried in the blood. Higher levels are linked to more heart disease.
Low certaintyResults and what it means
Why it was measured
It is the usual blood marker used in diet trials for heart risk.
Statistical vs. clinical meaning
A small average rise in short trials; larger with unfiltered coffee.
Safety implication
Relevant for people with high cholesterol.
| Study | Result | People | Product |
|---|---|---|---|
| 2 | LDL +5.4 mg/dl (95% CI 1.4 to 9.5) | 1,017 people in 12 randomised trials in Western countries | Coffee, average 45 days |
Triglycerides
Raised in trials
A type of fat in the blood.
Low certaintyResults and what it means
Why it was measured
Raised levels are a heart risk marker.
Statistical vs. clinical meaning
A small average rise in short trials.
Safety implication
None specific.
| Study | Result | People | Product |
|---|---|---|---|
| 2 | Triglycerides +12.6 mg/dl (the abstract prints the interval as '3.5, 12.6') | 12 randomised trials | Coffee, average 45 days |
Other 4
Systolic blood pressure
No significant change in trials
The top number in a blood pressure reading.
Mixed findingsResults and what it means
Why it was measured
High blood pressure is a major heart risk.
Statistical vs. clinical meaning
No significant change for coffee, but an umbrella review reports a rise with caffeine.
Safety implication
People with high blood pressure should ask their clinician.
| Study | Result | People | Product |
|---|---|---|---|
| 10 | Systolic -0.55 mmHg (95% CI -2.46 to 1.36), not significant | 10 randomised trials, each at least 1 week | Coffee versus less or no coffee |
Glucose tolerance and insulin sensitivity
No significant change in trials
How well the body handles a sugar load and responds to insulin.
Low certaintyResults and what it means
Why it was measured
These are early markers for type 2 diabetes risk.
Statistical vs. clinical meaning
One small trial; it did not move these measures.
Safety implication
None specific.
| Study | Result | People | Product |
|---|---|---|---|
| 11 | No significant differences in glucose tolerance, insulin sensitivity or insulin secretion between coffee and water groups | 45 healthy overweight adults | 5 cups a day of instant coffee, caffeinated or decaffeinated, 8 weeks |
Total sleep time
Lowered in trials
The number of minutes slept at night.
Moderate certaintyResults and what it means
Why it was measured
It is the most direct measure of whether caffeine costs sleep.
Statistical vs. clinical meaning
Clear average losses in sleep with caffeine; individual sensitivity varies.
Safety implication
Relevant for anyone who has trouble sleeping.
| Study | Result | People | Product |
|---|---|---|---|
| 4 | Total sleep time -45 minutes; sleep efficiency -7%; time to fall asleep +9 minutes; waking after sleep onset +12 minutes | 24 studies of caffeine and night-time sleep | Caffeine from several sources, including coffee, versus none |
Recurrence of atrial fibrillation or flutter
Lowered in trials
Return of an irregular heart rhythm after a procedure to restore normal rhythm.
Low certaintyResults and what it means
Why it was measured
It is the main outcome of the DECAF trial.
Statistical vs. clinical meaning
One open-label trial.
Safety implication
Heart patients should follow their cardiologist.
| Study | Result | People | Product |
|---|---|---|---|
| 12 | Recurrence 47% with coffee versus 64% with abstinence (HR 0.61, 95% CI 0.42 to 0.89) | 200 coffee-drinking adults after cardioversion | Regular caffeinated coffee versus abstinence, 6 months |
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 10
- Pregnancy: evidence conflicts and official limits are on caffeine. Observational studies link high coffee intake in pregnancy with low birth weight, preterm birth and pregnancy loss (BMJ umbrella review). A genetics-based study found no change in miscarriage, stillbirth or preterm birth and suggests coffee might not itself cause these outcomes; it is not a trial. The NHS says no more than 200 mg of caffeine a day in pregnancy, EFSA says intakes up to 200 mg a day do not raise safety concerns for the foetus, and ACOG says moderate intake below 200 mg a day does not appear to be a major contributing factor in miscarriage or preterm birth. FDA advises talking to a health care provider if pregnant or trying to become pregnant. Ask your midwife or doctor. Mixed 8 1 20 14 13 15
- Caffeine affects sleep, nerves and heart rate in some people. FDA cites 400 mg of caffeine a day as an amount not generally associated with negative effects for most adults, and says sensitivity and how fast the body clears caffeine vary widely. MedlinePlus lists restlessness, shakiness, insomnia, headaches, dizziness, fast heart rate, dehydration, anxiety and dependency as problems with too much caffeine. A pooled analysis of 24 studies found caffeine cut total sleep time by about 45 minutes. A cup of coffee has about 95 mg of caffeine (USDA) and FDA lists 113 to 247 mg in 12 fluid ounces of regular brewed coffee. Authoritative guidance 15 19 4 22
- High blood pressure or heart rhythm problems: ask your clinician. MedlinePlus says caffeine increases blood pressure and advises people with arrhythmia or high blood pressure to check with a health care provider about limiting caffeine. An umbrella review reports caffeine linked with a rise in blood pressure in trials, while a meta-analysis of 10 coffee trials found no significant change. One 2026 trial in 200 coffee drinkers with atrial fibrillation after cardioversion found less recurrence with coffee than with abstinence, which goes against older advice; it was a single open-label trial. Mixed 19 5 10 12
- Some medicines may interact with caffeine. MedlinePlus says to check with a health care provider about interactions between caffeine and medicines or supplements, including stimulants, certain antibiotics, asthma medicines and heart medicines. It does not name specific medicines. FDA says caffeine that occurs naturally in coffee is handled by the body the same as added caffeine, so count all sources. Ask your pharmacist. Authoritative guidance 19 15
- Cholesterol: unfiltered coffee raised blood fats in trials. A meta-analysis of 12 randomised trials found that drinking coffee for about 45 days raised total cholesterol by 8.1 mg/dl, LDL cholesterol by 5.4 mg/dl and triglycerides by 12.6 mg/dl on average. The total cholesterol rise was greater with unfiltered coffee. If you have high cholesterol, ask your clinician or dietitian. Randomised trials meta analysis 2
- Reflux, stomach upset and ulcers. A 2026 meta-analysis found GERD slightly more common in coffee users (OR 1.18) but of unclear clinical meaning, and no link with Barrett's esophagus. MedlinePlus says caffeine increases stomach acid, sometimes causing an upset stomach or heartburn, and advises people with GERD or ulcers to check with a health care provider. Observational 7 19
- Very hot drinks, not coffee itself, are linked with oesophageal cancer. IARC (2016) classified coffee drinking as not classifiable as to carcinogenicity (Group 3) and drinking very hot beverages as probably carcinogenic to humans (Group 2A) for oesophageal cancer. IARC's director said it is the temperature, rather than the drinks themselves, that appears responsible. Authoritative guidance 18
- Children and teens. FDA says medical experts advise against energy drinks for children and teens, and that the Dietary Guidelines for Americans say drinks containing caffeine should be avoided for children younger than 2. MedlinePlus says children can be especially sensitive to caffeine. EFSA applies its single-dose figure for adults to children and adolescents. Ask a paediatrician before giving coffee to a child. Authoritative guidance 15 19 14
- Bones: a link in women, direction not given in the abstract. The BMJ umbrella review found an association between coffee drinking and fracture in women but not in men, and suggested women at increased fracture risk possibly be excluded from future coffee trials. The abstract does not state the direction. MedlinePlus says caffeine may interfere with the absorption of calcium. Ask your clinician if you have osteoporosis or a high fracture risk. Observational 8 19
- Stopping suddenly after regular use. MedlinePlus says people who regularly consume caffeine and then stop suddenly may have withdrawal: headaches, drowsiness, irritability, nausea and trouble concentrating, usually gone after a couple of days. Authoritative guidance 19
Side effects 6
| Effect | How often | Severity and recovery | Evidence |
|---|---|---|---|
| Restlessness, shakiness, insomnia, headaches, dizziness, fast heart rate, anxiety and dehydration with too much caffeine MedlinePlus lists these for caffeine in general; sensitivity varies by person. | No frequency given | mild to moderate Not described. | Authoritative guidance 19 |
| Shorter and lighter sleep Caffeine from several sources, not coffee alone. | Total sleep time -45 min, sleep efficiency -7% on average (24 studies) | mild Not described. | Meta-analysis 4 |
| Slightly more acid reflux (GERD) Clinical meaning unclear, per the authors. | 34.9% in coffee users versus 30.7% in non-users (OR 1.18) | mild Not described. | Observational 7 |
| Higher total cholesterol, LDL and triglycerides Larger with unfiltered coffee. | Average rises of 8.1, 5.4 and 12.6 mg/dl after about 45 days | mild Not described. | Randomised trials meta analysis 2 |
| Rise in blood pressure (caffeine) A coffee-only meta-analysis found no significant change; the findings are mixed. | Not given | mild to moderate Not described. | Meta analyses of trials 5 19 |
| Withdrawal symptoms (headache, drowsiness, irritability, nausea, trouble concentrating) after stopping regular use | Not given | mild Usually gone after a couple of days. | Authoritative guidance 19 |
Liver
No liver injury from drinking coffee was found in the sources read. A liver-safety source such as LiverTox was not searched. Observational studies link coffee with a lower risk of liver cancer; that is not a safety finding for people who already have liver disease. 9
How often. No frequency was found.
Monitoring. No agency monitoring advice was found.
This is a safety connection. It is not evidence that Coffee supports liver health.
Medicines and supplements 4
| With | Why it matters | Importance | Evidence | What to do |
|---|---|---|---|---|
| Stimulant medicines, certain antibiotics, asthma medicines and heart medicines prescription | MedlinePlus names these classes as possible interaction groups with caffeine but gives no mechanism or specific medicine. | Not specified. Only the general advice to check with a health care provider was read. | Authoritative guidance Low certainty 19 | Ask your pharmacist or prescriber whether coffee or caffeine matters for your medicines. |
| Other caffeine sources (energy drinks, tea, cola, caffeine pills, some supplements and medicines) food-and-supplement | Caffeine from different sources adds up; FDA says the body handles natural and added caffeine the same way. | Effects from several sources can add up, so limits apply to the total. | Authoritative guidance Moderate certainty 15 14 | Count caffeine from all sources. |
| Medicines for blood pressure or heart rhythm prescription | Caffeine can raise blood pressure and heart rate, which in theory could work against these medicines. | No source read tied coffee to a specific interaction with these medicines. This is a general caution, not a documented interaction. | Theoretical Not enough evidence 19 | Tell your clinician how much coffee you drink. |
| Calcium and bone medicines supplement | MedlinePlus says caffeine may interfere with the absorption of calcium. | Not quantified in the source read. | Authoritative guidance Very low certainty 19 8 | Ask your clinician if you have low bone density. |
Who should check first 7
| Situation | Advice | Evidence |
|---|---|---|
| Pregnancy or trying to become pregnant | Official limits are set on caffeine, not coffee: 200 mg a day (NHS, EFSA; ACOG says moderate intake below 200 mg a day does not appear to be a major factor in miscarriage or preterm birth). FDA advises talking to a health care provider. Ask your midwife or doctor. | Authoritative guidance 20 14 13 15 |
| Breastfeeding | FDA recommends talking to a health care provider about limiting caffeine. MedlinePlus says a small amount of caffeine you consume passes to your baby. EFSA's 200 mg figure is for pregnant and lactating women. | Authoritative guidance 15 19 14 |
| Heart rhythm problems or high blood pressure | MedlinePlus advises checking with a health care provider about limiting caffeine. Follow your cardiologist's advice; one 2026 trial found less atrial fibrillation recurrence with coffee, but it was a single open-label trial. | Authoritative guidance 19 12 |
| Sleep problems, anxiety, migraines or other chronic headaches | MedlinePlus advises checking with a health care provider about limiting or avoiding caffeine. | Authoritative guidance 19 |
| Reflux or ulcers | MedlinePlus advises checking with a health care provider. The 2026 meta-analysis found slightly more reflux in coffee users. | Authoritative guidance 19 7 |
| Children and teens | FDA, citing the Dietary Guidelines, says caffeinated drinks should be avoided for children younger than 2, and medical experts advise against energy drinks for children and teens. Ask a paediatrician. | Authoritative guidance 15 |
| High cholesterol | Trials found coffee raised cholesterol, more with unfiltered coffee. Ask your clinician. | Randomised trials meta analysis 2 |
Overdose, product quality and regulators
Summary. No toxicity from coffee as an ordinary drink was found in the sources read. The safety points are caffeine, pregnancy, sleep, blood pressure and medicines. FDA says large amounts of caffeine may pose a danger to health.
Animal. Not reviewed.
High dose or long term signals. FDA and MedlinePlus list the effects of too much caffeine (see Adverse effects). EFSA's figures: up to 400 mg a day for healthy adults, single doses of 100 mg may affect sleep close to bedtime.
Overdose response. Not found.
Genotoxicity. Not researched.
Acrylamide from roasting, mould toxins and pesticide residues in coffee were not researched. The two quality points read are brew method (unfiltered coffee raised cholesterol in trials) and drink temperature (very hot drinks).
Brew method. The cholesterol rise in trials was greater with unfiltered coffee. 2
Very hot drinks. IARC: very hot beverages are probably carcinogenic to humans for oesophageal cancer (Group 2A); the temperature appears to be responsible. 18
Caffeine content varies. FDA lists 113 to 247 mg of caffeine in 12 fluid ounces of regular brewed non-specialty coffee; amounts differ by product and cup size, and restaurants are not required to list caffeine. 15
| Body | Action | Date |
|---|---|---|
| US FDA (United States) | Spilling the Beans: 400 mg of caffeine a day cited as an amount not generally associated with negative effects for most adults (about two to three 12 fl oz cups of coffee); regular brewed non-specialty coffee 113 to 247 mg per 12 fl oz; decaf typically 2 to 15 mg per 8 fl oz; people who are pregnant, trying to become pregnant or breastfeeding should talk to a health care provider. source | 2024-08-28 |
| EFSA (European Food Safety Authority) (European Union) | Scientific Opinion on the safety of caffeine: up to 400 mg a day throughout the day does not raise safety concerns for healthy adults, except pregnant women; up to 200 mg a day does not raise safety concerns for the foetus; single doses of 100 mg may affect sleep, particularly close to bedtime. source | 2015-05-27 |
| NHS (UK) (United Kingdom) | Foods to avoid in pregnancy: no more than 200 mg of caffeine a day; too much caffeine has been linked to a higher chance of miscarriage and stillbirth. source | 2026-06-15 |
| ACOG (American College of Obstetricians and Gynecologists) (United States) | Committee Opinion 462: moderate caffeine consumption (less than 200 mg per day) does not appear to be a major contributing factor in miscarriage or preterm birth; the relationship to growth restriction remains undetermined. source | 2010-08 |
| IARC (WHO) (International) | Monographs Volume 116: coffee drinking not classifiable as to carcinogenicity (Group 3); very hot beverages probably carcinogenic to humans (Group 2A) for oesophageal cancer. source | 2016-06-15 |
| MedlinePlus (US National Library of Medicine) (United States) | Caffeine: up to 400 mg a day is not harmful for most people; who should limit caffeine; possible medicine interactions; withdrawal. source | 2021-09-08 |
When to get medical help
- Chest pain, fainting, or a very fast or irregular heartbeat after coffee or other caffeine: seek urgent medical help (call 911 or your local emergency number if severe)
- Severe agitation, confusion or repeated vomiting after a large amount of caffeine from drinks, pills or powders: seek urgent medical help
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 coffee?
Is coffee good for you?
Large reviews link moderate coffee drinking with lower risk of early death, heart disease and type 2 diabetes, but these are observational links and cannot show coffee is the cause. Trials show a rise in cholesterol with unfiltered coffee, and caffeine affects sleep. Whether coffee suits you depends on your health.
Does coffee help you live longer?
Is decaf as good as regular coffee?
Does coffee raise blood pressure?
Does coffee raise cholesterol?
It can. In 12 trials, coffee for about 45 days raised total cholesterol by 8.1 mg/dl and LDL by 5.4 mg/dl on average, more with unfiltered coffee.
Does coffee lower the risk of type 2 diabetes?
Is coffee safe in pregnancy?
Evidence conflicts. Observational studies link high intake with adverse outcomes, while a genetics-based study found no change in miscarriage, stillbirth or preterm birth. The NHS and EFSA give 200 mg of caffeine a day, and ACOG says moderate intake below 200 mg a day does not appear to be a major factor in miscarriage or preterm birth. Ask your midwife or doctor.
Does coffee cause acid reflux?
Does coffee affect sleep?
Can coffee interact with medicines?
Does coffee cause cancer?
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Editorial transparency
- Written by
- AlternativeMed editorial team. Research compiled with AI assistance, then checked against the sources listed.
- Medical review
- None. This page has not been reviewed by a physician or pharmacist.
- First published
- 2026-10-26
- Last substantive update
- 2026-10-26
- How we research
- We started from our existing coffee summary, re-checked nutrition against saved USDA FoodData Central data, read the agency pages (FDA, EFSA, NHS, ACOG, MedlinePlus, IARC press release) and re-read PubMed abstracts for reviews, trials and cohort analyses. Only abstracts were read for studies. Items we could not verify are flagged in the research gaps.
- 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. No study abstract read states coffee industry funding; funding is not stated in several abstracts.
Sources 22
Each source was opened and checked. Where we read only the abstract, it says so. The small numbers in the text point here.
- Brito Nunes C, Huang P, Wang G, Lundberg M, D'Urso S, Wootton RE, Borges MC, Lawlor DA, Warrington NM, Evans DM, Hwang LD, Moen GH. Mendelian randomization study of maternal coffee consumption and its influence on birthweight, stillbirth, miscarriage, gestational age and pre-term birth.. Int J Epidemiol. 2023. PMID 35679582. DOI 10.1093/ije/dyac121. (abstract)
- Cai L, Ma D, Zhang Y, Liu Z, Wang P. The effect of coffee consumption on serum lipids: a meta-analysis of randomized controlled trials.. Eur J Clin Nutr. 2012. PMID 22713771. DOI 10.1038/ejcn.2012.68. (abstract)
- Ding M, Bhupathiraju SN, Chen M, van Dam RM, Hu FB. Caffeinated and decaffeinated coffee consumption and risk of type 2 diabetes: a systematic review and a dose-response meta-analysis.. Diabetes Care. 2014. PMID 24459154. DOI 10.2337/dc13-1203. (abstract)
- Gardiner C, Weakley J, Burke LM, Roach GD, Sargent C, Maniar N, Townshend A, Halson SL. The effect of caffeine on subsequent sleep: A systematic review and meta-analysis.. Sleep Med Rev. 2023. PMID 36870101. DOI 10.1016/j.smrv.2023.101764. (abstract)
- Grosso G, Godos J, Galvano F, Giovannucci EL. Coffee, Caffeine, and Health Outcomes: An Umbrella Review.. Annu Rev Nutr. 2017. PMID 28826374. DOI 10.1146/annurev-nutr-071816-064941. (abstract)
- Li Q, Liu Y, Sun X, Yin Z, Li H, Cheng C, Liu L, Zhang R, Liu F, Zhou Q, Wang C, Li L, Wang B, Zhao Y, Zhang M, Hu D. Caffeinated and decaffeinated coffee consumption and risk of all-cause mortality: a dose-response meta-analysis of cohort studies.. J Hum Nutr Diet. 2019. PMID 30786114. DOI 10.1111/jhn.12633. (abstract)
- Muftah M, McCarty TR, Hartnett D, Flanagan R, Hiramoto B, Chan WW. Association of Coffee Intake With Risk of Gastroesophageal Reflux Disease and Complications: A Systematic Review and Meta-Analysis.. Clin Transl Gastroenterol. 2026. PMID 41677121. DOI 10.14309/ctg.0000000000000996. (abstract)
- Poole R, Kennedy OJ, Roderick P, Fallowfield JA, Hayes PC, Parkes J. Coffee consumption and health: umbrella review of meta-analyses of multiple health outcomes.. BMJ. 2017. PMID 29167102. DOI 10.1136/bmj.j5024. (abstract)
- Sang LX, Chang B, Li XH, Jiang M. Consumption of coffee associated with reduced risk of liver cancer: a meta-analysis.. BMC Gastroenterol. 2013. PMID 23433483. DOI 10.1186/1471-230X-13-34. (abstract)
- Steffen M, Kuhle C, Hensrud D, Erwin PJ, Murad MH. The effect of coffee consumption on blood pressure and the development of hypertension: a systematic review and meta-analysis.. J Hypertens. 2012. PMID 23032138. DOI 10.1097/HJH.0b013e3283588d73. (abstract)
- Wedick NM, Brennan AM, Sun Q, Hu FB, Mantzoros CS, van Dam RM. Effects of caffeinated and decaffeinated coffee on biological risk factors for type 2 diabetes: a randomized controlled trial.. Nutr J. 2011. PMID 21914162. DOI 10.1186/1475-2891-10-93. (abstract)
- Wong CX, Cheung CC, Montenegro G, Oo HH, Peña IJ, Tang JJ, Tu SJ, Wall G, Dewland TA, Moss JD, Gerstenfeld EP, Tseng ZH, Hsia HH, Lee RJ, Olgin JE, Vedantham V, Scheinman MM, Lee C, Sanders P, Marcus GM. Caffeinated Coffee Consumption or Abstinence to Reduce Atrial Fibrillation: The DECAF Randomized Clinical Trial.. JAMA. 2026. PMID 41206802. DOI 10.1001/jama.2025.21056. (abstract)
- . ACOG Committee Opinion 462: Moderate Caffeine Consumption During Pregnancy. . . (full-text)
- . EFSA: Caffeine (Scientific Opinion on the safety of caffeine, published 27 May 2015). . . (full-text)
- . US FDA: Spilling the Beans: How Much Caffeine is Too Much?. . . (full-text)
- . GBIF Backbone: Coffea arabica L. (usageKey 2895345). . . (full-text)
- . GBIF Backbone: Coffea canephora Pierre ex A.Froehner (usageKey 2895528). . . (full-text)
- . IARC press release no. 244: IARC Monographs evaluate drinking coffee, mate, and very hot beverages (15 June 2016). . . (full-text)
- . MedlinePlus (US National Library of Medicine): Caffeine. . . (full-text)
- . NHS (UK): Foods to avoid in pregnancy. . . (full-text)
- . PubChem: caffeine (CID 2519) and riboflavin (CID 493570). . . (full-text)
- . USDA FoodData Central 171890: Beverages, coffee, brewed, prepared with tap water (SR Legacy, April 2018). . . (full-text)
