Vitamins & Supplements · Supplement formula

Greens Powders: What They Contain and What They Do Not Replace

Powdered greens and superfood blends · also called Greens powder, green superfood powder, powdered greens, polvo de verduras, superalimentos en polvo

A greens powder is a dried mix of plants and sometimes algae, seaweed, extracts, probiotics, fibre and added vitamins, sold to stir into water. Very few trials test a finished powder, and none we read compared one with eating vegetables. The main cautions are vitamin K for people on warfarin, iodine from kelp, contaminants in algae ingredients, and labels that hide how much of each ingredient is inside.

General information, not medical advice. Last substantive update October 26, 2026 · Not medically reviewed. A named clinician has not signed off on this page. How this page is made

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About Greens Powders: What They Contain and What They Do Not Replace

A greens powder is a mix, and the label tells you what is in your product. No study we read shows that a scoop gives the same benefits as the vegetables public health advice is about. The main cautions are vitamin K and warfarin, iodine from seaweed, contaminants in algae, and hidden amounts in blends.

What greens powders are

Greens powders are dried plant material, sometimes with algae, seaweed, extracts, probiotics, fibre and added vitamins and minerals, ground into a powder to mix into water or a drink. They also come as capsules, tablets and ready-made drinks.

They are sold to people who want to add vegetables to their day, and for gut comfort, energy and immunity. Contents differ widely from one product to the next.

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What is usually inside

Common ingredient groups are dried leafy vegetables, grasses and grains such as wheatgrass and barley grass, spirulina and chlorella, kelp and other seaweed, green tea extract, added probiotics, fibre, and vitamins and minerals.

Each group has its own page and its own cautions: leafy vegetables bring vitamin K, seaweed can bring iodine, green tea extract has a rare liver warning, and algae have been found with contaminants. Powders may also be blended with mushrooms or protein.

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Reading the label

US labels list ingredients in a Supplement Facts panel. If a product uses a proprietary blend, the label must give the blend's total weight and list its ingredients in order of weight, but not the amount of each. A long list can therefore hide very small amounts of any one item.

Serving size matters too: a panel describes one serving, and the % Daily Value shows how much of a nutrient one serving adds compared with the reference amount. Gummies, capsules and powders list their serving differently. Check for algae, kelp and green tea extract, and for added vitamins you may already take.

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Powders versus vegetables

The NHS says a portion of fruit or vegetables is 80 g, and its 5 A Day advice rests on a World Health Organization minimum of 400 g a day. It says different fruit and vegetables bring different mixes of fibre, vitamins, minerals and other nutrients, and lists fresh, frozen, canned, dried or juiced produce. It does not mention powders.

No study we read tested whether a powder counts as a portion or matches whole vegetables. Amounts of nutrients in powders and in vegetable portions were not read from USDA or NIH sources, so none are stated here.

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What the research shows

Only one trial of a finished powder was found: 30 healthy adults, 4 weeks, with authors linked to the maker. It found no harm to digestion or blood tests and no clear benefit. A 6-month trial of fruit, vegetable and berry capsules in 34 older adults was open-label and gave early signals for homocysteine and blood pressure, which the authors call hypothesis-generating.

We found no trials of greens powders for energy, weight, detox or immunity. Results for single ingredients, such as spirulina and blood pressure, belong to those ingredients and are not added up as if the blend were tested.

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At a glance

Traditional uses history, not proof

Sold as a convenient way to add vegetables to the day
Marketed for energy, gut comfort, detox and immunity; these are marketing claims, not findings

Studied for research

Standing in for fruit and vegetables, insufficient evidence
Heart-related blood markers (juice powder capsules), very low certainty
Digestive comfort and gut bacteria, insufficient evidence
Colds (fruit and vegetable capsules), low certainty
Algae ingredients and blood pressure, low certainty
Energy, detox, weight and immunity claims, insufficient evidence

Main compounds

Dried leafy vegetables (vitamin K)
Grasses such as wheatgrass and barley grass
Spirulina and chlorella
Kelp and other seaweed (iodine)
Green tea extract
Added probiotics, fibre, vitamins and minerals

Common forms

Powder in a tub or sachet
Capsules or tablets
Ready-to-drink or liquid shots
Blends with mushrooms or protein

Research links: 2017 review: fruit and vegetable intake and risk of heart disease, cancer and death (95 studies) · 2024 trial: a multi-ingredient powder versus placebo (30 adults) · 2026 trial: fruit, vegetable and berry capsules in older adults · 2017 lab study: cyanotoxins in algae supplements · 2016 review: dietary vitamin K and anticoagulants · Research Library · Genes & Biomarkers Library

What it is and its history

Accepted scientific name: Greens powders (powdered greens and superfood powder blends)
Common names: Greens powder (English); Green superfood powder (English); Powdered greens (English); Vegetable powder blend (English); Polvo de verduras (Spanish); Superalimentos en polvo (Spanish)
Family or group: Supplement formula: a powder blend. Common ingredient groups are dried leafy vegetables, grasses and grains, algae, seaweed, green tea extract, added probiotics and fibre, and added vitamins and minerals.
Harvest and processing: Made by drying and grinding plant or algae material and mixing it, sometimes with extracts, probiotics, fibre and added vitamins or minerals. The process steps and what is lost in drying were not read from a source.
Look-alikes and adulterants: Name: Multivitamins; Note: Vitamin and mineral tablets or capsules; they have their own page.; Name: Mushroom blends; Note: Powders of fungi, sometimes mixed with greens; they have their own page.; Name: Plant protein powders; Note: Protein-focused powders; they have their own page.; Name: Fruit and vegetable juice powder capsules; Note: The product type tested in the cold and heart-marker trials on this page; not the same as a greens powder.; Name: Fiber supplements; Note: Single-fibre products; they have their own page.
Sustainability and conservation: Not assessed.

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
Vitamin K (phylloquinone) from leafy vegetables	vitamin	Leaves Not read from a source for powders.	Needed for blood clotting; the NHS lists green leafy vegetables such as broccoli and spinach as sources and says high-vitamin-K foods can affect warfarin. ^{22 23 15}	Human data
Spirulina and chlorella (microalgae)	algae	Whole dried algae Not read from a source.	Studied alone for blood pressure; lab surveys found contaminants in some products. ^{8 13 12}	Human data
Kelp and other seaweed	seaweed	Whole dried seaweed Iodine content of powders was not read from a source.	A source of iodine; a case report links kelp tablets to transient hyperthyroidism. ^{3 21}	Human case report
Wheatgrass and other young grasses	grass	Young shoots Not read from a source.	Review says it contains chlorophyll, vitamins, minerals, flavonoids, phenolic compounds and polysaccharides; no direct gut studies found. ¹	Review
Green tea extract	plant extract	Leaf extract Not read from a source for powders.	Liver injury is uncommon but reported with extracts; can lower atorvastatin levels (NCCIH). ^{18 7}	Human guidance
Added probiotics	live microbes	Not read from a source.	In the 4-week powder trial, two probiotic species rose in stool tests and likely came from the product. ⁵	Human data

Mechanisms, receptors and pathways

Target or pathway	Gene or receptor	What was found	Level
Vitamin K and clotting	Not specified in the sources read	The NHS says vitamin K is needed for blood clotting and that foods high in vitamin K can affect how warfarin works. A 2016 review found conflicting evidence and no firm rule for diet changes. ^{22 23 15}	Human data
Algae soaking up contaminants	Not specified in the sources read	A 2025 study says spirulina and chlorella have a high biosorption capacity, which raises concerns that they accumulate contaminants from the water they grow in. ¹³	Laboratory
Cyanotoxin damage in the liver	Serine/threonine protein phosphatases (per review)	A 2026 review says major cyanotoxins disrupt protein phosphatase signaling, mitochondria and redox balance in the liver, causing oxidative stress and inflammation. This is mostly lab evidence and the exposure from supplements is unclear. ⁹	Laboratory
Green tea extract and drug levels	Not specified in the sources read	NCCIH says green tea extract can reduce blood levels of atorvastatin. The mechanism is not stated in the page read. ¹⁸	Human data
Gut bacteria	Not specified in the sources read	After 4 weeks of a multi-ingredient powder, stool tests showed more of two probiotic species and some other bacteria changes; the authors think the probiotic species came from the product. ⁵	Human data

Absorption, metabolism and elimination

Absorption: Not found for greens powders.
Distribution: Not found.
Metabolism: Not found.
Elimination: Not found.
Bioavailability: Whether nutrients in a dried powder are absorbed like those in whole vegetables was not shown in the sources read.

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Isolated compounds versus whole extracts

A powder is a dried, ground, processed product, often mixed with extracts and additives. The NHS says different fruit and vegetables bring different mixes of fibre, vitamins, minerals and other nutrients, and its 5 A Day advice counts fresh, frozen, canned, dried or juiced produce by the 80 g portion. It does not mention powders. No study read compared a powder with the same vegetables, so whether the powder keeps the same fibre and plant compounds is unknown.

Nutritional composition

No USDA or NIH food amounts were read for this page, so no per-portion amounts are stated. The NHS names green leafy vegetables such as broccoli and spinach as vitamin K sources.

7benefits and uses looked at

26studies and sources checked

Low certaintybest evidence rating found

3lab markers tracked in trials

2 low certainty1 very low certainty4 not enough evidence

What was looked at

The 7 benefits and uses checked for Greens Powders: What They Contain and What They Do Not Replace, each with how strong the evidence is. Tap one to open it.

Standing in for whole fruit and vegetablesNot enough evidence
Blood pressure, homocysteine and cholesterol (fruit and vegetable juice powder concentrates)Very low certainty
Digestive comfort and gut bacteriaNot enough evidence
Colds (fruit and vegetable capsules)Low certainty
Spirulina and chlorella ingredients and blood pressureLow certainty
Wheatgrass and gut healthNot enough evidence
Energy, detox, weight and immunity claims for greens powdersNot enough evidence

Lab markers tracked in the studies

Homocysteine and blood pressureDigestive quality of life scoreDays with cold symptoms

What is Greens Powders: What They Contain and What They Do Not Replace good for?

The studied uses and how strong the human evidence is for each. Most results come from one or two small trials, and several come from juice powder concentrates or single algae ingredients, not from greens powders.

Standing in for whole fruit and vegetablesNot enough evidenceNo trial we read compared a greens powder with eating vegetables, so there is no evidence that a scoop gives the same benefits. The strong evidence is for whole fruit and vegetables eaten as food. A 2017 pooled analysis of 95 studies linked eating more of them to lower risks of heart disease and early death, but that kind of study shows a link, not a cause. Blood pressure, homocysteine and cholesterol (fruit and vegetable juice powder concentrates)Very low certaintyThe closest trials are of fruit, vegetable and berry juice powder concentrates in capsules, not of greens powders. A 2019 review of such trials leaned positive for cholesterol, homocysteine and blood pressure. A 2026 six-month trial in 34 older adults was open-label and small, and its authors call the results hypothesis-generating. Digestive comfort and gut bacteriaNot enough evidenceOne 4-week trial in 30 healthy adults tested a commercial multi-ingredient powder against placebo. The powder did not make digestion worse, and bowel habits and stool form did not differ. A hint of better digestive quality of life (p = 0.058) was not statistically significant. Stool tests showed more of two probiotic species that likely came from the product itself. Colds (fruit and vegetable capsules)Low certaintyOne 2011 trial in 529 healthcare workers found about 2 fewer days of moderate or severe cold symptoms over 6 months with fruit and vegetable capsules than with placebo. Total days with any cold symptoms did not differ. It tested one product that is not a greens powder, and it has not been repeated in the sources we read. Spirulina and chlorella ingredients and blood pressureLow certaintySpirulina and chlorella are common ingredients in greens powders. A 2025 pooled analysis of trials found chlorella had no effect on blood pressure or blood fats. Spirulina was linked with a very small fall in diastolic blood pressure that the authors call of uncertain clinical significance. These were trials of the algae alone, not of any blend. Wheatgrass and gut healthNot enough evidenceA 2026 review of wheatgrass found no human or animal studies that directly tested its effect on gut bacteria. Its claims rest on lab and compound studies, so benefits for the gut are unproven. Energy, detox, weight and immunity claims for greens powdersNot enough evidenceGreens powders are marketed for energy, detox, weight loss, immunity and skin. We found no randomised trial of a finished greens powder on these outcomes. The two trials of finished multi-ingredient powders we read measured digestive tolerance and safety markers, not energy or weight.

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.

Standing in for whole fruit and vegetables

Not enough evidence

No trial we read compared a greens powder with eating vegetables, so there is no evidence that a scoop gives the same benefits. The strong evidence is for whole fruit and vegetables eaten as food. A 2017 pooled analysis of 95 studies linked eating more of them to lower risks of heart disease and early death, but that kind of study shows a link, not a cause.

3 studiesWhole fruit and vegetables eaten as food in the analysis. Powders wer…

Studies, doses and limits

What the trials found

The 2017 analysis pooled prospective studies of whole fruit and vegetables eaten as food. Per 200 g a day, the summary relative risk was 0.92 for cardiovascular disease and 0.90 for death from any cause. Risk kept falling up to about 800 g a day. We found no trial or cohort that tested a powder in place of produce.

Results

Whole fruit and vegetables: a link with lower risk in observational studies. Greens powders: nothing tested against food.

Effect sizes as reported

Per 200 g a day of whole fruit and vegetables: cardiovascular disease RR 0.92 (95% CI 0.90 to 0.95); all-cause mortality RR 0.90 (95% CI 0.87 to 0.93); total cancer RR 0.97 (95% CI 0.95 to 0.99).

Why this rating

Insufficient for powders because no study compared a powder with produce. The link for whole produce comes from observational studies, which cannot prove cause, and the analysis itself found large differences between studies for death from any cause (I-squared 83%).

Form and dose studied

Whole fruit and vegetables eaten as food in the analysis. Powders were not studied.

Who was studied

Adults in prospective cohort studies from many countries.

Limits

Observational. People who eat more produce may also differ in other healthy habits. Says nothing about dried powders.

Why researchers looked

Many people eat fewer fruit and vegetables than public health advice suggests, and greens powders are sold as an easy way to fill the gap.

Traditional use

Public advice such as the NHS 5 A Day is about whole fruit and vegetables: one portion is 80 g, and the advice rests on a World Health Organization minimum of 400 g a day. The NHS says different fruit and vegetables bring different mixes of fibre, vitamins, minerals and other nutrients, and lists fresh, frozen, canned, dried or juiced produce as counting. It does not mention powders.

Proposed mechanism Not established

Not established. No study read explains why whole produce is linked with better health, or whether a dried powder keeps the same mix of fibre and other substances.

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

See the Safety tab for vitamin K, iodine, contamination and label cautions that apply to powders but not to eating vegetables.

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Blood pressure, homocysteine and cholesterol (fruit and vegetable juice powder concentrates)

Very low certainty

The closest trials are of fruit, vegetable and berry juice powder concentrates in capsules, not of greens powders. A 2019 review of such trials leaned positive for cholesterol, homocysteine and blood pressure. A 2026 six-month trial in 34 older adults was open-label and small, and its authors call the results hypothesis-generating.

2 studiesCapsules of one commercial fruit, vegetable and berry juice powder co…

Studies, doses and limits

What the trials found

The 2019 systematic review looked at total cholesterol, LDL cholesterol, homocysteine, systolic blood pressure and body mass index and reported a positive and significant role for concentrates on selected markers (numbers are not in the abstract). In the 2026 trial, 18 people took six capsules a day and 16 were controls for 6 months. Homocysteine stayed stable in the capsule group but rose in the control group. After adjusting for baseline values, age and weight, differences held for homocysteine and diastolic blood pressure, but not for systolic blood pressure or a marker of protein damage.

Results

Small, early signals on blood markers. Not shown to prevent heart disease.

Effect sizes as reported

2026 trial interaction p-values: homocysteine p = 0.002, diastolic blood pressure p = 0.011, systolic blood pressure p = 0.036 before adjustment (no longer significant after adjustment). The 2019 review gave no numbers in its abstract.

Why this rating

Very low because the best recent trial is small, open-label (people knew what they took), reports an early time point, and has authors linked to the product's maker. The review pools trials of several concentrates and its abstract gives no sizes.

Form and dose studied

Capsules of one commercial fruit, vegetable and berry juice powder concentrate (six a day in the 2026 trial). Amounts are in the studies table. This is not a greens powder.

Who was studied

Generally healthy older adults (2026 trial); adults in the trials pooled by the 2019 review.

Limits

Small numbers, open-label design, company-affiliated authors, blood markers rather than heart attacks or strokes, and results for one product that do not carry over to other powders.

Why researchers looked

Fruit and vegetable intake is linked with heart health, so researchers asked whether concentrated juice powders move heart-related blood markers.

Traditional use

Fruit and vegetable juice powders are sold as a way to add produce to the diet. They are a different product from leafy greens powders, grass powders or algae.

Proposed mechanism Not established

Not established. The trial authors measured markers of oxidative stress but did not show how a concentrate acts.

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

The 2026 trial reported no safety-relevant deteriorations in liver, kidney, thyroid, fat or sugar markers over 6 months.

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Digestive comfort and gut bacteria

Not enough evidence

One 4-week trial in 30 healthy adults tested a commercial multi-ingredient powder against placebo. The powder did not make digestion worse, and bowel habits and stool form did not differ. A hint of better digestive quality of life (p = 0.058) was not statistically significant. Stool tests showed more of two probiotic species that likely came from the product itself.

1 studiesOne commercial powder, taken daily for 4 weeks. Product contents and …

Studies, doses and limits

What the trials found

15 men and 15 women were randomised to the powder or placebo for 4 weeks. Neither group worsened on the digestive quality of life questionnaire, bowel frequency or stool form scales. Digestive quality of life score rose 62.5% with the powder versus a 50% reduction with placebo, but p = 0.058, which does not meet the usual cut-off. Blood tests (blood count, chemistry, fats) did not change significantly.

Results

No harm shown over 4 weeks; no clear benefit shown. Gut-bacteria changes included the product's own probiotic species.

Effect sizes as reported

Digestive quality of life +62.5% versus -50% with placebo (p = 0.058, d = 0.73); not statistically significant.

Why this rating

Insufficient because it is one small, short trial, the main digestive result was not significant, and two authors are employees of the product's company while others have received funding from supplement companies.

Form and dose studied

One commercial powder, taken daily for 4 weeks. Product contents and amounts are in the studies table.

Who was studied

Healthy men and women (15 each).

Limits

Only 30 people, 4 weeks, one product. Healthy people, so it says nothing about people with gut problems. Results do not carry to other powders.

Why researchers looked

Powders often add probiotics, fibre and plant material, so researchers asked whether they change gut bacteria or how people feel.

Traditional use

Greens powders are sold for gut health and regularity. These claims come from marketing; this is one early study.

Proposed mechanism Authors interpretation

Not established. The authors suggest the extra probiotic species probably came from the product's own probiotic ingredients.

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

No clinical safety markers changed significantly in this trial.

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Colds (fruit and vegetable capsules)

Low certainty

One 2011 trial in 529 healthcare workers found about 2 fewer days of moderate or severe cold symptoms over 6 months with fruit and vegetable capsules than with placebo. Total days with any cold symptoms did not differ. It tested one product that is not a greens powder, and it has not been repeated in the sources we read.

1 studiesFour capsules a day of one commercial fruit and vegetable juice powde…

Studies, doses and limits

What the trials found

Healthcare workers (mostly nursing staff, 80% women, mean age about 40) took four capsules a day or matching placebo for 8 months, with symptoms counted over 6 months by diary. Days with moderate or severe symptoms: 7.6 with the supplement and 9.5 with placebo (p = 0.023). Days with any symptoms: 29.4 versus 30.7 (p = 0.616).

Results

A modest fall in the more severe cold days, no change in total cold days. One trial.

Effect sizes as reported

Moderate or severe cold days 7.6 (95% CI 6.5 to 8.8) versus 9.5 (8.4 to 10.6), p = 0.023; any symptom days 29.4 versus 30.7, p = 0.616.

Why this rating

Low because it is a single placebo-controlled trial of one product in one group, with a mixed result (the main outcome differed, the total days did not), and it is old (2011).

Form and dose studied

Four capsules a day of one commercial fruit and vegetable juice powder product for 8 months. Not a greens powder.

Who was studied

Healthcare professionals aged 18 to 65 at one university hospital in Berlin.

Limits

One product, one workplace group with high exposure to patients, results may not carry to other people or powders. The abstract does not state who funded it.

Why researchers looked

Researchers asked whether the nutrients and plant compounds in concentrated produce help the body resist colds.

Traditional use

Immune claims are common in marketing for greens and produce powders.

Proposed mechanism Not established

Not established.

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

The abstract does not report side effects.

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Spirulina and chlorella ingredients and blood pressure

Low certainty

Spirulina and chlorella are common ingredients in greens powders. A 2025 pooled analysis of trials found chlorella had no effect on blood pressure or blood fats. Spirulina was linked with a very small fall in diastolic blood pressure that the authors call of uncertain clinical significance. These were trials of the algae alone, not of any blend.

1 studiesSpirulina or chlorella supplements alone; amounts varied by trial.

Studies, doses and limits

What the trials found

The 2025 analysis found 12 studies of chlorella and 9 of spirulina. For spirulina, diastolic blood pressure changed by -0.42 (95% CI -0.81 to -0.02, p = 0.04; units not given in the abstract). Blood fat measures did not change significantly. Chlorella had a neutral effect.

Results

Spirulina: tiny change in diastolic pressure. Chlorella: no effect. Neither result tests a finished greens powder.

Effect sizes as reported

Spirulina diastolic BP -0.42 (95% CI -0.81 to -0.02), p = 0.04; total cholesterol -0.17 (95% CI -0.39 to 0.06), p = 0.15.

Why this rating

Low because the effect is tiny, trials are small and varied, and two authors work for a seaweed company. It is also an ingredient result, so it cannot be added to a blend's result.

Form and dose studied

Spirulina or chlorella supplements alone; amounts varied by trial.

Who was studied

Adults in 12 chlorella and 9 spirulina trials (about 100 to 300 people per outcome).

Limits

Small effect, uncertain clinical meaning, mixed study designs. See the Safety tab for contamination concerns with algae supplements.

Why researchers looked

Algae contain protein, minerals and plant pigments, so researchers tested them on heart risk factors.

Traditional use

Spirulina and chlorella are eaten or sold as dietary supplements in many countries.

Proposed mechanism Not established

Not established.

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

Algae products have been found with cyanotoxins and metals in lab tests; see the Safety tab.

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Wheatgrass and gut health

Not enough evidence

A 2026 review of wheatgrass found no human or animal studies that directly tested its effect on gut bacteria. Its claims rest on lab and compound studies, so benefits for the gut are unproven.

1 studiesNot applicable.

Studies, doses and limits

What the trials found

The review searched databases up to June 2025 and found no intervention studies, in people or animals, that directly looked at wheatgrass and gut bacteria.

Results

No direct evidence.

Effect sizes as reported

No effect sizes; no direct studies found.

Why this rating

Insufficient because the review found no direct studies of the outcome.

Limits

A narrative review, not a trial; its claims about gut inflammation come from lab and indirect work.

Why researchers looked

Wheatgrass and other young grasses contain chlorophyll, vitamins, minerals and plant compounds, so they are often added to greens powders.

Traditional use

Wheatgrass is a popular juice and powder ingredient. This page does not describe any traditional use.

Proposed mechanism Hypothesis

Proposed only. The review says wheatgrass compounds may act as prebiotics, antioxidants or immune modulators, based on mechanism and compound studies.

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

Not assessed in the review's abstract.

Energy, detox, weight and immunity claims for greens powders

Not enough evidence

Greens powders are marketed for energy, detox, weight loss, immunity and skin. We found no randomised trial of a finished greens powder on these outcomes. The two trials of finished multi-ingredient powders we read measured digestive tolerance and safety markers, not energy or weight.

3 studiesNot applicable.

Studies, doses and limits

What the trials found

PubMed searches on 2026-10-26 found no such trials. The one 4-week powder trial and the 6-month capsule trial looked at safety and digestive or heart markers.

Results

No evidence found.

Why this rating

Insufficient because no trial of the claimed outcomes was found in our searches. A search can miss studies, so this means none found, not none exist.

Limits

Based on our own searches of PubMed only.

Why researchers looked

These are common marketing claims, so we checked whether trials exist.

Traditional use

Marketing claims only.

Proposed mechanism Not established

Not established.

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

See the Safety tab.

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Connections to the rest of health

How Greens Powders: What They Contain and What They Do Not Replace 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	Evidence status	Context	Studies
Balanced Nutrition	Not enough evidence	Standing in for whole fruit and vegetables: No trial we read compared a greens powder with eating vegetables, so there is no evidence that a scoop gives the same benefits. The strong evidence is for whole fruit and vegetables eaten as food. A 2017 pooled analysis of 95 studies linked eating more of them to lower risks of heart disease and early death, but that kind of study shows a link, not a cause.	^{2 20 25}
Preventive Wellness	Not enough evidence	Standing in for whole fruit and vegetables: No trial we read compared a greens powder with eating vegetables, so there is no evidence that a scoop gives the same benefits. The strong evidence is for whole fruit and vegetables eaten as food. A 2017 pooled analysis of 95 studies linked eating more of them to lower risks of heart disease and early death, but that kind of study shows a link, not a cause.	^{2 20 25}
Heart Health	Very low certainty	Blood pressure, homocysteine and cholesterol (fruit and vegetable juice powder concentrates): The closest trials are of fruit, vegetable and berry juice powder concentrates in capsules, not of greens powders. A 2019 review of such trials leaned positive for cholesterol, homocysteine and blood pressure. A 2026 six-month trial in 34 older adults was open-label and small, and its authors call the results hypothesis-generating.	^{6 16}
Blood Pressure Support	Very low certainty	Blood pressure, homocysteine and cholesterol (fruit and vegetable juice powder concentrates): The closest trials are of fruit, vegetable and berry juice powder concentrates in capsules, not of greens powders. A 2019 review of such trials leaned positive for cholesterol, homocysteine and blood pressure. A 2026 six-month trial in 34 older adults was open-label and small, and its authors call the results hypothesis-generating.	^{6 16}
Digestive Health	Not enough evidence	Digestive comfort and gut bacteria: One 4-week trial in 30 healthy adults tested a commercial multi-ingredient powder against placebo. The powder did not make digestion worse, and bowel habits and stool form did not differ. A hint of better digestive quality of life (p = 0.058) was not statistically significant. Stool tests showed more of two probiotic species that likely came from the product itself.	⁵
Gut Health	Not enough evidence	Digestive comfort and gut bacteria: One 4-week trial in 30 healthy adults tested a commercial multi-ingredient powder against placebo. The powder did not make digestion worse, and bowel habits and stool form did not differ. A hint of better digestive quality of life (p = 0.058) was not statistically significant. Stool tests showed more of two probiotic species that likely came from the product itself.	⁵
Immune Support	Low certainty	Colds (fruit and vegetable capsules): One 2011 trial in 529 healthcare workers found about 2 fewer days of moderate or severe cold symptoms over 6 months with fruit and vegetable capsules than with placebo. Total days with any cold symptoms did not differ. It tested one product that is not a greens powder, and it has not been repeated in the sources we read.	¹¹
Blood Pressure Support	Low certainty	Spirulina and chlorella ingredients and blood pressure: Spirulina and chlorella are common ingredients in greens powders. A 2025 pooled analysis of trials found chlorella had no effect on blood pressure or blood fats. Spirulina was linked with a very small fall in diastolic blood pressure that the authors call of uncertain clinical significance. These were trials of the algae alone, not of any blend.	⁸
Heart Health	Low certainty	Spirulina and chlorella ingredients and blood pressure: Spirulina and chlorella are common ingredients in greens powders. A 2025 pooled analysis of trials found chlorella had no effect on blood pressure or blood fats. Spirulina was linked with a very small fall in diastolic blood pressure that the authors call of uncertain clinical significance. These were trials of the algae alone, not of any blend.	⁸
Gut Health	Not enough evidence	Wheatgrass and gut health: A 2026 review of wheatgrass found no human or animal studies that directly tested its effect on gut bacteria. Its claims rest on lab and compound studies, so benefits for the gut are unproven.	¹
Digestive Support	Not enough evidence	Wheatgrass and gut health: A 2026 review of wheatgrass found no human or animal studies that directly tested its effect on gut bacteria. Its claims rest on lab and compound studies, so benefits for the gut are unproven.	¹
Energy Boost	Not enough evidence	Energy, detox, weight and immunity claims for greens powders: Greens powders are marketed for energy, detox, weight loss, immunity and skin. We found no randomised trial of a finished greens powder on these outcomes. The two trials of finished multi-ingredient powders we read measured digestive tolerance and safety markers, not energy or weight.	^{25 5 16}
Weight Management	Not enough evidence	Energy, detox, weight and immunity claims for greens powders: Greens powders are marketed for energy, detox, weight loss, immunity and skin. We found no randomised trial of a finished greens powder on these outcomes. The two trials of finished multi-ingredient powders we read measured digestive tolerance and safety markers, not energy or weight.	^{25 5 16}
Immune Support	Not enough evidence	Energy, detox, weight and immunity claims for greens powders: Greens powders are marketed for energy, detox, weight loss, immunity and skin. We found no randomised trial of a finished greens powder on these outcomes. The two trials of finished multi-ingredient powders we read measured digestive tolerance and safety markers, not energy or weight.	^{25 5 16}

B. Body systems

Connected to	Kind of connection	Evidence status	Context	Studies
Nutrition	Biological association	Not enough evidence	Studied for: Standing in for whole fruit and vegetables	^{2 20 25}
Whole Body	Biological association	Not enough evidence	Studied for: Standing in for whole fruit and vegetables Studied for: Energy, detox, weight and immunity claims for greens powders	^{2 20 25 5 16}
Cardiovascular System	Biological association	Very low certainty	Studied for: Blood pressure, homocysteine and cholesterol (fruit and vegetable juice powder concentrates) Studied for: Spirulina and chlorella ingredients and blood pressure	^{6 16 8}
Blood	Biological association	Very low certainty	Studied for: Blood pressure, homocysteine and cholesterol (fruit and vegetable juice powder concentrates)	^{6 16}
Digestive System	Biological association	Not enough evidence	Studied for: Digestive comfort and gut bacteria Studied for: Wheatgrass and gut health	^{5 1}
Gut Health	Biological association	Not enough evidence	Studied for: Digestive comfort and gut bacteria	⁵
Immune System	Biological association	Low certainty	Studied for: Colds (fruit and vegetable capsules)	¹¹
Respiratory System	Biological association	Low certainty	Studied for: Colds (fruit and vegetable capsules)	¹¹

C. Body parts and organs

Connected to	Kind of connection	Evidence status	Context	Studies
Thyroid	Adverse effect or risk	Case report	Kelp tablets were followed by transient hyperthyroidism in one case report; the NHS says high iodine over long periods could change thyroid function. Kelp tablets were followed by a temporary overactive thyroid in one case report. Preparation or compound: Kelp or other seaweed in a powder	^{3 21}
Liver	Adverse effect or risk	Documented risk	Liver injury is uncommon but reported, mainly with green tea extracts in tablet or capsule form. Preparation or compound: Green tea extract and multi-ingredient supplements	^{18 7}

I. Biomarkers

Connected to	Kind of connection	Evidence status	Context	Studies
Homocysteine and blood pressure	Biological association	Very low certainty	Measured in trials: homocysteine stayed stable versus a rise in controls; diastolic pressure lower after adjustment. A lab change is not the same as a health benefit.	¹⁶
Digestive quality of life score	Biological association	Not enough evidence	Measured in trials: no worse; trend upward, not significant. A lab change is not the same as a health benefit.	⁵
Days with cold symptoms	Biological association	Low certainty	Measured in trials: fewer moderate or severe days; total days unchanged. A lab change is not the same as a health benefit.	¹¹

K. Biological pathways

Connected to	Kind of connection	Evidence status	Context	Studies
Vitamin K	Preliminary mechanism	Human	Leafy greens supply it; relevant to people taking warfarin.	^{22 23}
Iodine	Preliminary mechanism	Human case report	Kelp and seaweed can add iodine.	^{21 3}

L. Active compounds

Connected to	Kind of connection	Evidence status	Context	Studies
Vitamin K (phylloquinone) from leafy vegetables	Biological association	Human	Needed for blood clotting; the NHS lists green leafy vegetables such as broccoli and spinach as sources and says high-vitamin-K foods can affect warfarin. Preparation or compound: Leaves	^{22 23 15}
Spirulina and chlorella (microalgae)	Biological association	Human	Studied alone for blood pressure; lab surveys found contaminants in some products. Preparation or compound: Whole dried algae	^{8 13 12}
Kelp and other seaweed	Biological association	Human case report	A source of iodine; a case report links kelp tablets to transient hyperthyroidism. Preparation or compound: Whole dried seaweed	^{3 21}
Wheatgrass and other young grasses	Biological association	Review	Review says it contains chlorophyll, vitamins, minerals, flavonoids, phenolic compounds and polysaccharides; no direct gut studies found. Preparation or compound: Young shoots	¹
Green tea extract	Biological association	Human guidance	Liver injury is uncommon but reported with extracts; can lower atorvastatin levels (NCCIH). Preparation or compound: Leaf extract	^{18 7}
Added probiotics	Biological association	Human	In the 4-week powder trial, two probiotic species rose in stool tests and likely came from the product.	⁵

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).

Evidence at a glance: what the research found for 7 outcomes

2Low certainty

1Very low certainty

4Not enough evidence

Each outcome below is one thing researchers measured. Certainty is how far the evidence can be trusted, not how well it works. The full studies are on the next tab.

Standing in for whole fruit and vegetables 3 studies Not enough evidence Blood pressure, homocysteine and cholesterol (fruit and vegetable juice powder concentrates) 2 studies Very low certainty Digestive comfort and gut bacteria 1 study Not enough evidence Colds (fruit and vegetable capsules) 1 study Low certainty Spirulina and chlorella ingredients and blood pressure 1 study Low certainty Wheatgrass and gut health 1 study Not enough evidence Energy, detox, weight and immunity claims for greens powders 3 studies Not enough evidence

The evidence

The research centre for Greens Powders: What They Contain and What They Do Not Replace. 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 greens powder summary, then re-read PubMed abstracts for every review, trial, case report and lab study cited, and read the NHS, NCCIH and FDA pages named. Only abstracts were read for papers. NIH Office of Dietary Supplements pages could not be read and are marked unverified.

Study library: every study we checked 26

Design Research type Year from Search

Study	Design	People	Product, dose, length	Result
Alva 2026 From Chlorophyll to Micro Biome: Wheatgrass's Role in Gut Health-A Comprehensive Review. Int J Prev Med · PMID 42921282 · DOI	Narrative review	Literature on wheatgrass and gut health, searched to June 2025	Wheatgrass (Triticum aestivum) Juice or powder, varied	No human or animal intervention studies directly testing wheatgrass on gut microbiome composition were found; mechanism and compound studies suggest possible effects. No effect sizes (Not applicable) Methods, limits and funding Outcomes: Gut microbiome composition, gut inflammation, mucosal integrity Limitations: Narrative review; direct evidence is limited. Funding and conflicts: The authors declare no conflicts of interest. Read: abstract
Aune 2017 Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality-a systematic review and dose-response meta-analysis of prospective studies. Int J Epidemiol · PMID 28338764 · DOI	Systematic review meta analysis	95 prospective studies (142 publications) of fruit and vegetable intake and cardiovascular disease, cancer and death	Whole fruit and vegetables eaten as food Food (not a supplement) Per 200 g a day in the analysis Follow-up varied by study · vs Lower versus higher intake	Higher intake was linked with lower risk of cardiovascular disease, cancer and early death. Risk fell up to about 800 g a day (600 g for cancer). Per 200 g a day: cardiovascular disease RR 0.92; total cancer RR 0.97; all-cause mortality RR 0.90 (CVD 0.90 to 0.95; cancer 0.95 to 0.99; all-cause 0.87 to 0.93 (I-squared 83% for all-cause)) Methods, limits and funding Outcomes: Coronary heart disease, stroke, cardiovascular disease, total cancer, all-cause mortality Limitations: Observational; shows links, not cause. Whole food, not powders. Funding and conflicts: No conflict statement in the record read. Read: abstract
Gherbon 2019 Transient Hyperthyroidism following the ingestion of complementary medications containing kelp seaweed: A case-report. Medicine (Baltimore) · PMID 31517826 · DOI	Case report	1 A 70-year-old woman with obesity and high blood pressure, no previous thyroid disease	Slimming tablets containing kelp Tablets Not given About 3 months before symptoms	Transient hyperthyroidism 3 months after taking kelp tablets; normal thyroid function returned after stopping them and 3 months of antithyroid medicine. Not applicable (Not applicable) Methods, limits and funding Outcomes: Heart rate, thyroid function Limitations: A single case; the amount of kelp or iodine in the tablets was not given in the abstract. Funding and conflicts: The authors have no conflicts of interest to disclose. Read: abstract
Kejžar 2020 Characterization of Algae Dietary Supplements Using Antioxidative Potential, Elemental Composition, and Stable Isotopes Approach. Front Nutr · PMID 33614692 · DOI	Laboratory analysis n/a	Algae products from the Slovenian market: kelps, Spirulina, Chlorella and Aphanizomenon flos-aquae	Algae dietary supplements (lab analysis) Retail products · vs Maximum allowed values	Levels of arsenic, cadmium, mercury and lead were below the maximum allowed values. The authors say Spirulina and Chlorella need analyses with more samples. Not given in the abstract (Not applicable) Methods, limits and funding Outcomes: Elemental composition, antioxidant potential, stable isotopes Limitations: One country's market; small number of samples. Funding and conflicts: The authors declare no commercial or financial conflicts. Read: abstract
La Monica 2024 The effects of AG1® supplementation on the gut microbiome of healthy adults: a randomized, double-blind, placebo-controlled clinical trial. J Int Soc Sports Nutr · PMID 39352252 · DOI	Randomised controlled trial	30 15 healthy men and 15 healthy women	Commercial multi-ingredient greens powder (named in the paper's title) Powder, mixed into a drink Daily; amount per day not given in the abstract 4 weeks · vs Placebo	No negative effect on digestive quality of life or stool habits. Two probiotic species were enriched, likely from the product. Clinical safety markers did not change significantly. Digestive quality of life score rose 62.5% versus a 50% fall with placebo (p = 0.058). DQLQ +62.5% vs -50%, p = 0.058, d = 0.73 (Not given in the abstract) Methods, limits and funding Outcomes: Gut bacteria (stool sequencing), digestive quality of life, bowel frequency, stool form, blood tests Limitations: Small, short, healthy volunteers, one product. The main digestive outcome was not significant. Funding and conflicts: Two authors are employees of the product's company (Athletic Greens International). Two others report funding, honoraria or consulting fees from supplement companies. The statement says the funders had no role in collecting or analysing the data. Treat as industry-linked. Registration: NCT06181214 Read: abstract
Lorenzoni 2019 Fruit and Vegetable Concentrate Supplementation and Cardiovascular Health: A Systematic Review from a Public Health Perspective. J Clin Med · PMID 31717327 · DOI	Systematic review	Trials of fruit and vegetable concentrate supplements (number of trials not given in the abstract)	Fruit and vegetable concentrates Powder or capsule (forms varied) Varied by trial Varied · vs Placebo or control	The authors report a positive and significant role for concentrate supplements on selected risk markers and then modelled possible public health effects. Numbers not given in the abstract (Not given in the abstract) Methods, limits and funding Outcomes: Total cholesterol, LDL, homocysteine, systolic blood pressure, body mass index Limitations: Abstract gives no trial count, sizes or trial quality. Includes a simulation model, which is not evidence from people. Concentrates are not greens powders. Funding and conflicts: The authors declare no conflict of interest. Read: abstract
Navarro 2017 Liver injury from herbal and dietary supplements. Hepatology · PMID 27677775 · DOI	Narrative review	Expert symposium review of liver injury from herbal and dietary supplements	Herbal and dietary supplements Various	Herbal and dietary supplements account for about 20% of drug-induced liver injury cases in the US. The main implicated agents are anabolic steroids, green tea extract and multi-ingredient nutritional supplements; for multi-ingredient products the responsible component is usually unknown. About 20% of cases (Not applicable) Methods, limits and funding Outcomes: Liver injury cases and implicated products Limitations: Expert review of a symposium, not a systematic review. Funding and conflicts: The record read gave no conflict statement; support is listed from US public research funders. Read: abstract
Pinto-Leite 2025 The Role of Chlorella and Spirulina as Adjuvants of Cardiovascular Risk Factor Control: A Systematic Review and Meta-Analysis of Randomised Controlled Trials. Nutrients · PMID 40289965 · DOI	Systematic review meta analysis	12 trials of chlorella and 9 of spirulina on cardiovascular risk factors (168 to 279 and 101 to 299 people per outcome)	Chlorella and spirulina supplements Oral, forms varied Varied by trial Varied · vs Placebo or control	Chlorella: neutral effect on blood pressure and blood fats. Spirulina: small fall in diastolic blood pressure; no significant change in blood fats. Spirulina diastolic BP -0.42 (units not in abstract), p = 0.04 (-0.81 to -0.02 (diastolic BP); total cholesterol -0.39 to 0.06) Methods, limits and funding Outcomes: Blood pressure, blood fats, glucose, weight Limitations: Small effect of uncertain clinical significance; small, varied trials. Funding and conflicts: Two authors are employed by Sea4Us (a company); the remaining authors declare none. Read: abstract
Rajput 2026 Health risks of cyanotoxin contamination in dietary supplements: Mechanistic insights into organ-specific toxicity. Food Chem Toxicol · PMID 42874982 · DOI	Narrative review human and lab	Review of cyanotoxins in Arthrospira (spirulina), Aphanizomenon flos-aquae and Chlorella supplements	Cyanobacteria and microalgae supplements Retail products	Calls cyanotoxin contamination an emerging public health concern and says gaps remain on chronic low-dose exposure, absorption from supplements and long-term human effects. Much of the toxicity evidence is mechanistic. No effect sizes (Not applicable) Methods, limits and funding Outcomes: Cyanotoxin occurrence and organ-specific toxicity Limitations: Review; human data on supplements are limited. Funding and conflicts: The authors declare no competing interests. Read: abstract
Rhoades 2023 Microbiota and Cyanotoxin Content of Retail Spirulina Supplements and Spirulina Supplemented Foods. Microorganisms · PMID 37317149 · DOI	Laboratory analysis n/a	5 retail spirulina products (2 supplements, 3 foods)	Spirulina products (lab analysis) Retail products · vs Recommended daily limits	Potentially pathogenic bacteria, including Bacillus cereus and Klebsiella pneumoniae, were detected. Microcystins were found in all products at levels that could lead to exceeding recommended daily limits. The authors link the problems to open-pond production. Microcystins in 5 of 5 products (Not applicable) Methods, limits and funding Outcomes: Bacteria (culture and sequencing) and cyanotoxins by ELISA Limitations: Only 5 products; ELISA tests can differ from other methods. Funding and conflicts: The authors declare no conflict of interest. Read: abstract
Roll 2011 Reduction of common cold symptoms by encapsulated juice powder concentrate of fruits and vegetables: a randomised, double-blind, placebo-controlled trial. Br J Nutr · PMID 20727236 · DOI	Randomised controlled trial	529 Healthcare professionals aged 18 to 65 at a Berlin university hospital (263 supplement, 266 placebo)	Fruit and vegetable juice powder concentrate (a named commercial product) Capsules Four capsules a day (studied in the trial) 8 months, including a 2-month run-in; symptoms counted over 6 months · vs Matching placebo	About 20% fewer moderate or severe cold-symptom days; total days with any symptoms were similar. 7.6 vs 9.5 days (p = 0.023); any-symptom days 29.4 vs 30.7 (p = 0.616) (7.6 (6.5 to 8.8) vs 9.5 (8.4 to 10.6)) Methods, limits and funding Outcomes: Days with moderate or severe common cold symptoms (primary), diary-based Limitations: One product, one setting, 80% women, self-reported symptoms. Not a greens powder. Funding and conflicts: No conflict statement in the record read; funding not stated in the abstract. Read: abstract
Roy-Lachapelle 2017 Detection of Cyanotoxins in Algae Dietary Supplements. Toxins (Basel) · PMID 28245621 · DOI	Laboratory analysis n/a	18 commercial products containing spirulina or Aphanizomenon flos-aquae	Algae dietary supplements (lab analysis) Retail products · vs Tolerable daily intake values	8 of 18 products contained cyanotoxins above tolerable daily intake values. 8 of 18 products above tolerable daily intake values (Not applicable) Methods, limits and funding Outcomes: Cyanotoxins: microcystins, anatoxins, cylindrospermopsin, saxitoxin, BMAA Limitations: 18 products from one survey; not a market-wide survey. Funding and conflicts: The authors declare no conflict of interest. Read: abstract
Sochacka 2025 Spirulina and Chlorella Dietary Supplements-Are They a Source Solely of Valuable Nutrients? Int J Mol Sci · PMID 41226507 · DOI	Laboratory analysis n/a	52 spirulina and chlorella products (29 conventional, 23 organic)	Spirulina and chlorella products (lab analysis) Retail products · vs EU limits for toxic metals	All samples met EU limits for toxic metals. Pharmaceutical residues were found, with caffeine most frequent, then metronidazole, carbamazepine, benzocaine and tramadol. A concern was raised for aluminium (percent of tolerable weekly intake). No significant organic versus conventional differences. Not given as single numbers in the abstract (Not applicable) Methods, limits and funding Outcomes: Heavy metals (ICP-MS) and pharmaceutical residues (LC-MS/MS) Limitations: Lab survey; residue amounts and health meaning were not given in the abstract. Funding and conflicts: The authors declare no conflicts of interest. Read: abstract
Vankawala 2025 Over-the-Counter Supplement Overuse: A Rare Potential Cause of Arsenic Poisoning and Bradycardia. Cureus · PMID 41510484 · DOI	Case report	1 A 71-year-old woman who took 26 supplements for 5 years and had high urine arsenic	Many supplements, including algae products Oral About 5 years	Urine arsenic was 111.8 micrograms per litre; the authors judged arsenic exposure from supplements a likely contributor to her symptoms. Algae-based supplements are noted as prone to arsenic. Not applicable (Not applicable) Methods, limits and funding Outcomes: Slow heart rate, cognitive decline, fatigue, urine arsenic Limitations: A single case; cause not proven; many supplements were taken together. Funding and conflicts: The authors declare no conflicts of interest. Read: abstract
Violi 2016 Interaction Between Dietary Vitamin K Intake and Anticoagulation by Vitamin K Antagonists: Is It Really True?: A Systematic Review. Medicine (Baltimore) · PMID 26962786 · DOI	Systematic review	Two dietary trials and nine observational studies of dietary vitamin K and anticoagulation	Dietary vitamin K intake (food) Food Median dietary vitamin K1 intake ranged from 76 to 217 micrograms a day across studies Varied · vs Lower versus higher intake	Conflicting evidence. An effect on clotting may be seen only at high intakes (above about 150 micrograms a day). The authors say evidence does not support advising people to change their diet when starting these drugs, and suggest keeping vitamin K intake steady. Not given as a single number (Not given in the abstract) Methods, limits and funding Outcomes: INR (a measure of blood clotting) and anticoagulation control in people taking vitamin K antagonists Limitations: Studies mixed different reasons for taking the drugs and different INR targets; the review excluded vitamin K supplement studies. Funding and conflicts: The authors have no conflicts of interest to disclose. Read: abstract
Ziegler 2026 Effects of a Commercial Fruit, Vegetable and Berry Juice Powder Concentrate on Metabolic Safety and Cardiovascular Health in Older Adults: 6-Month Results of a Randomized Controlled Trial. Nutrients · PMID 42738920 · DOI	Randomised controlled trial	34 Generally healthy older adults; 18 took capsules, 16 were controls; 6-month point of a 1-year trial	Commercial fruit, vegetable and berry juice powder concentrate Capsules Six capsules a day (studied in the trial) 6 months (of 1 year) · vs Control group with no capsules (open-label)	Well tolerated, with no safety-relevant deteriorations. Homocysteine stayed stable in the capsule group but rose in controls; diastolic blood pressure was lower. After adjustment, systolic blood pressure and carbonyl proteins no longer reached significance. Interaction p: homocysteine 0.002; diastolic BP 0.011; systolic BP 0.036 (attenuated after adjustment); carbonyl proteins 0.030 (attenuated) (Not given in the abstract) Methods, limits and funding Outcomes: Primary: metabolic safety (liver, kidney, thyroid, fat, sugar markers). Exploratory: oxidative stress markers, homocysteine, blood pressure, vitamin C level Limitations: Open-label (no placebo), 34 people, early time point, exploratory outcomes. The authors call the findings hypothesis-generating. Funding and conflicts: Funding listed in the record: Green Beat (Austria). Two authors are affiliated with Green Beat Institute of Nutrient Research; the others declare no conflicts. Registration: NCT04763291 Read: abstract
s-fda-labeling-guide FDA: Dietary Supplement Labeling Guide, Chapter IV, Nutrition Labeling · Source	Regulator guidance n/a			Methods, limits and funding Read: full-text
s-nccih-green-tea NCCIH: Green Tea (last updated February 2025) · Source	Health agency n/a			Methods, limits and funding Read: full-text
s-nccih-using-wisely NCCIH: Using Dietary Supplements Wisely (last updated January 2019) · Source	Health agency n/a			Methods, limits and funding Read: full-text
s-nhs-5aday NHS: Why 5 A Day? (page last reviewed 2026-09-30) · Source	Reference database n/a			Methods, limits and funding Read: full-text
s-nhs-iodine NHS: Iodine (page last reviewed 2020-08-03) · Source	Reference database n/a			Methods, limits and funding Read: full-text
s-nhs-vitamin-k NHS: Vitamin K (page last reviewed 2020-08-03) · Source	Reference database n/a			Methods, limits and funding Read: full-text
s-nhs-warfarin NHS: Warfarin (page last reviewed 2026-02-24) · Source	Reference database n/a			Methods, limits and funding Read: full-text
s-ods-factsheets NIH Office of Dietary Supplements: fact sheets (vitamin K, iodine) · Source	Reference database n/a			Methods, limits and funding Read: not-read
s-pubmed-search-2026-10-26 PubMed searches run 2026-10-26 (search log, not a paper)	Search log n/a			Methods, limits and funding Read: search-only
s-site-summary Existing AlternativeMed greens powder summary (read 2026-10-26)	Internal summary n/a			Methods, limits and funding Read: summary-only

What we do not know yet

No trial compared a greens powder with eating vegetables.
No trials of greens powders for energy, weight, skin, immunity or disease risk were found.
No survey of metals, microbes or label accuracy in finished greens powders was found.
NIH Office of Dietary Supplements fact sheets could not be read, so no official upper limits are quoted.
Pregnancy, breastfeeding, children and kidney disease were not covered by any source read.
Long-term safety is unknown; the longest trial read lasted 6 months.

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".

Other 3

●

Homocysteine and blood pressure

Homocysteine stayed stable versus a rise in controls; diastolic pressure lower after adjustment in trials

Homocysteine is an amino acid in the blood; higher levels are linked with heart disease risk. Blood pressure is the force of blood on artery walls.

Very low certainty

Results and what it means

Why it was measured

To see whether a fruit, vegetable and berry concentrate changes heart-related markers in older adults.

Statistical vs. clinical meaning

Early signal in a small open-label trial; not proof of better heart health.

Safety implication

People on blood pressure medicines should not add supplements without asking their doctor or pharmacist.

Study	Result	People	Product
¹⁶	Homocysteine interaction p = 0.002 and diastolic blood pressure p = 0.011 persisted after adjustment; systolic blood pressure (p = 0.036) and carbonyl proteins (p = 0.030) did not.	34 generally healthy older adults, 6 months	Six capsules a day of a commercial fruit, vegetable and berry juice powder concentrate, versus no capsules

¹⁶

●

Digestive quality of life score

No worse; trend upward, not significant in trials

A questionnaire in which people rate how digestion affects daily life.

Not enough evidence

Results and what it means

Why it was measured

To see whether a daily powder changes how people feel digestively.

Statistical vs. clinical meaning

Not statistically significant; one small trial.

Safety implication

None found.

Study	Result	People	Product
⁵	Score rose 62.5% with the powder and fell 50% with placebo, p = 0.058, d = 0.73; neither group got worse.	30 healthy adults, 4 weeks	A commercial multi-ingredient powder versus placebo, daily

⁵

●

Days with cold symptoms

Fewer moderate or severe days; total days unchanged in trials

Self-reported diary count of days with moderate or severe cold symptoms.

Low certainty

Results and what it means

Why it was measured

To see whether fruit and vegetable capsules affect how often people feel ill with colds.

Statistical vs. clinical meaning

A modest difference in one trial; self-reported.

Safety implication

None reported in the abstract.

Study	Result	People	Product
¹¹	7.6 versus 9.5 moderate or severe days (p = 0.023); any-symptom days 29.4 versus 30.7 (p = 0.616).	529 healthcare workers, 6 months of counting	Four capsules a day of a fruit and vegetable juice powder concentrate versus placebo

¹¹

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 5

Vitamin K from leafy greens can matter if you take warfarin. The NHS says foods high in vitamin K, such as broccoli, spinach and other green leafy vegetables, can affect how warfarin works. People on warfarin can still eat them but should talk to their warfarin clinic, and the NHS says not to take vitamin K supplements while on warfarin. A 2016 systematic review found the evidence on food vitamin K and warfarin control conflicting and suggested a steady intake rather than avoidance. A powder made from leafy vegetables could change your intake in a way a clinic does not know about, and we did not find the vitamin K content of any greens powder in the sources read. Tell the warfarin clinic before starting or stopping one. Official guidance and systematic review ^{23 22 15}
Algae ingredients (spirulina, chlorella) can carry toxins, metals and other contaminants. Lab surveys of algae supplements found problems. In 18 spirulina and Aphanizomenon (blue-green algae) products, 8 had cyanotoxins above tolerable daily intake values. In 5 retail spirulina products, microcystin toxins were found in all, at levels that could lead to exceeding recommended daily limits, along with bacteria such as Bacillus cereus and Klebsiella pneumoniae. In 52 spirulina and chlorella products, toxic metals were within EU limits but pharmaceutical residues were found, caffeine most often, and aluminium raised a concern. A 2026 review calls cyanotoxin contamination an emerging concern with long-term effects unknown. These are small surveys of some products, not a verdict on every product, and we did not find a survey of finished greens powders. Laboratory analyses and review ^{12 10 13 9}
Kelp or other seaweed can add iodine that affects the thyroid. A case report describes a 70-year-old woman who developed transient hyperthyroidism (overactive thyroid) about 3 months after taking tablets containing kelp; it cleared after she stopped them and had treatment. The NHS says high doses of iodine for long periods could change how the thyroid works. Whether a given powder contains kelp, and how much iodine it supplies, depends on the label; no iodine content for greens powders was read. Case report and official guidance ^{3 21}
Green tea extract in a blend: rare liver injury and drug interactions. NCCIH (February 2025) says liver injury is uncommon but has been reported with green tea products, mainly extracts in tablet or capsule form, and that people with a specific immune gene variant may be especially susceptible. NCCIH also says green tea extract can lower blood levels of atorvastatin. A 2017 expert review said herbal and dietary supplements cause about 20% of drug-induced liver injury cases in the United States, with green tea extract and multi-ingredient products among the main causes, and that in multi-ingredient products the responsible ingredient is often unknown. Official guidance and expert review ^{18 7}
Proprietary blends hide how much of each ingredient you get. FDA labeling rules require a proprietary blend to be named with its total weight and its ingredients listed in order of weight, but not the amount of each. A long ingredient list can therefore hide very small amounts of any one ingredient. This also makes it hard to judge how much vitamin K, iodine or other nutrients you are getting. Regulator guidance ¹⁷

Side effects 6

Effect	How often	Severity and recovery	Evidence
No significant changes in blood tests after 4 weeks of one powder Short, small, company-linked. Says nothing about long-term use or other products.	30 healthy adults; no significant change in blood count, chemistry or fats	Not applicable Not applicable	Randomised trial ⁵
No safety-relevant deteriorations at 6 months with a fruit, vegetable and berry capsule product Open-label, small, company-affiliated authors. Not a greens powder.	34 older adults; liver, kidney, thyroid, fat and sugar markers	Not applicable Not applicable	Open label randomised trial ¹⁶
Overactive thyroid after kelp tablets Applies only to powders that contain kelp or similar seaweed.	One case report	Moderate; needed antithyroid medicine for 3 months Thyroid function became normal after stopping the tablets and treatment	Case report ³
Liver injury linked to green tea extract and multi-ingredient supplements Applies mainly to products that list green tea extract. The 2017 review says the cause is often unknown in multi-ingredient products.	Uncommon (NCCIH); about 20% of drug-induced liver injury cases in the US come from herbal and dietary supplements (2017 review)	Can be serious; some cases need hospital care Not stated in the sources read	Official guidance and expert review ^{18 7}
Possible arsenic exposure in a heavy supplement user A 71-year-old woman took 26 supplements for 5 years with smoothies; the authors judged algae supplements a likely contributor but could not prove it. Not specific to greens powders.	One case report	Serious: slow heart rate, memory problems, fatigue Not stated in the abstract	Case report ¹⁴
Stomach upset, gas or loose stools Users sometimes report these, but we found no figures in the sources read.	No rates given in the abstracts read	Not applicable Not applicable	Absence of evidence

Liver

NCCIH says liver injury from green tea products is uncommon but reported, mainly with extracts in tablet or capsule form. A 2017 expert review said herbal and dietary supplements cause about 20% of drug-induced liver injury in the US and that green tea extract and multi-ingredient products are among the main causes. In the two trials read (a powder and a capsule product), blood tests including liver markers showed no significant worsening. A liver-safety reference such as LiverTox was not opened. ^{18 7 5 16}

How often. Uncommon (NCCIH); no frequency for greens powders was found.

Monitoring. No agency monitoring advice was found.

This is a safety connection. It is not evidence that Greens Powders: What They Contain and What They Do Not Replace supports liver health.

Medicines and supplements 6

With	Why it matters	Importance	Evidence	What to do
Warfarin (and other vitamin K antagonists) prescription	Vitamin K is needed for clotting; leafy vegetables are rich in it and can affect how warfarin works.	The NHS says foods high in vitamin K can affect warfarin and advises talking to the warfarin clinic. A 2016 review found food vitamin K evidence conflicting and suggested keeping intake stable.	Official guidance and systematic review Moderate certainty ^{23 15}	Tell the warfarin clinic before starting, stopping or changing a greens powder.
Atorvastatin (cholesterol medicine) prescription	NCCIH says green tea extract can lower blood levels of atorvastatin. How it does so is not stated in the page read.	Relevant only if a powder contains green tea extract.	Official guidance Low certainty ¹⁸	Ask a pharmacist if your powder lists green tea extract.
Nadolol and raloxifene prescription	NCCIH says high doses of green tea lowered blood levels of nadolol, and an NCCIH-funded study showed an interaction with raloxifene.	Relevant only if a powder contains green tea or its extract.	Official guidance Low certainty ¹⁸	Ask a pharmacist.
Thyroid medicines and thyroid conditions prescription	Kelp and some seaweeds are high in iodine, which affects the thyroid.	The NHS says high iodine doses for long periods could change how the thyroid works. No study of greens powders and thyroid medicine was found.	Official guidance and case report Low certainty ^{21 3}	Ask a doctor if you have a thyroid condition and the powder lists kelp or seaweed.
Other supplements and multivitamins (stacking) supplement	Powders may add vitamins, minerals and herbs that you also get from other products.	No study of stacking with greens powders was found, and amounts in a blend are often not disclosed. This is reasoning, not a finding.	Absence of evidence Not enough evidence ¹⁷	List every product you take for a pharmacist.
Other prescription medicines (general) prescription	No mechanism found for most ingredients.	NCCIH says supplements can interact with medicines. No interaction study of a finished greens powder was found.	Absence of evidence Not enough evidence ¹⁹	Absence of a study is not proof of safety. Tell a doctor or pharmacist about all supplements.

Who should check first 8

Situation	Advice	Evidence
Taking warfarin	Talk to your warfarin clinic before using a powder made from leafy vegetables.	Official guidance ²³
Thyroid disease, or a powder that lists kelp or seaweed	Ask a doctor first; seaweed can add iodine.	Case report and official guidance ^{3 21}
Liver disease, or past liver trouble with a supplement	Ask a doctor before using any powder that lists green tea extract.	Official guidance and expert review ^{18 7}
Pregnancy and breastfeeding	NCCIH says many supplements have not been tested in pregnant women or nursing mothers. No safety study of greens powders in pregnancy was found. Ask a doctor or midwife.	Official guidance and absence of evidence ¹⁹
Children	NCCIH says many supplements have not been tested in children. No trial of greens powders in children was found. Ask a doctor first.	Official guidance and absence of evidence ¹⁹
Before surgery	NCCIH says some supplements may increase bleeding risk or affect anaesthesia. Tell the surgical team about any powder.	Official guidance ¹⁹
Kidney disease	No source read says anything about greens powders and kidney disease. Ask a doctor; this is a general precaution.	Absence of evidence
Allergy to a listed ingredient	Check the full ingredient list. No allergy data for greens powders were read.	Absence of evidence

Overdose, product quality and regulators

Summary. No poisoning or overdose reports specific to greens powders were found in the sources read. The documented concerns are contaminants in algae ingredients, iodine from kelp, and vitamin K for people on warfarin.

Animal. Not reviewed.

High dose or long term signals. Long-term safety was not found: the longest trial read was 6 months and used a juice powder concentrate in capsules.

Overdose response. Not found.

Genotoxicity. Not researched.

Product quality is the main safety question for this type. Lab surveys of algae ingredients found toxins, microbes, metals and drug residues in some products. We found no survey of finished greens powders, and no check of whether label amounts match what is inside.

Cyanotoxins in algae supplements. 8 of 18 spirulina or Aphanizomenon products contained cyanotoxins above tolerable daily intake values. ¹²

Microbes and microcystins in retail spirulina. All 5 products had microcystins; bacteria including Bacillus cereus and Klebsiella pneumoniae were found. The authors link this to open-pond production. ¹⁰

Metals and drug residues in spirulina and chlorella. 52 products met EU limits for toxic metals, yet drug residues were found (caffeine most often, then metronidazole, carbamazepine, benzocaine and tramadol). Aluminium raised concern about the tolerable weekly intake. Organic and conventional products did not differ significantly. ¹³

Toxic elements in algae products from one market. Arsenic, cadmium, mercury and lead were below the maximum allowed values in the Slovenian-market kelp, spirulina, chlorella and Aphanizomenon products tested. ⁴

Arsenic in a heavy supplement user. A case report links high urine arsenic to a regimen of 26 supplements, with algae supplements a likely contributor. ¹⁴

Body	Action	Date
FDA (United States) (United States)	Says a proprietary blend must carry its name and total weight, with ingredients in descending order of weight, but not amounts of each. source
NHS / UK Department of Health and Social Care (United Kingdom)	Vitamin K: green leafy vegetables are sources; taking 1 mg or less of vitamin K supplements a day is unlikely to cause harm. source	2020-08-03
NHS (United Kingdom)	Warfarin: do not take vitamin K supplements; foods high in vitamin K can affect how warfarin works; talk to the warfarin clinic. source	2026-02-24
NHS / UK Department of Health and Social Care (United Kingdom)	Iodine: high doses for long periods could change thyroid function; 0.5 mg or less a day of iodine supplements is unlikely to cause harm. source	2020-08-03
NCCIH (US National Center for Complementary and Integrative Health) (United States)	Green tea: liver injury uncommon but reported, mainly with extracts in tablet or capsule form; extract can lower atorvastatin levels. source	2025-02
NCCIH (United States)	Supplements may interact with medicines, may add risks before surgery, and many have not been tested in pregnancy, nursing or children. source	2019-01

When to get medical help

Swelling of the face, lips or tongue, hives, wheezing or trouble breathing after a powder: call emergency services.
Unusual bruising or bleeding, black stools or blood in urine in someone taking warfarin who has changed their greens intake: contact the warfarin clinic or a doctor at once.
Racing heart, shaking, weight loss, trouble sleeping or feeling hot after a powder that contains kelp: see a doctor and mention the powder.
Yellow skin or eyes, dark urine, pale stools or severe stomach pain after a powder that lists green tea extract: stop it and get medical help the same day.
Persistent vomiting, severe diarrhea or stomach pain after a powder: stop it and see a doctor.

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 in a greens powder?

It depends on the product. Common ingredients are dried leafy vegetables, grasses such as wheatgrass, spirulina and chlorella, seaweed, green tea extract, probiotics, fibre and added vitamins and minerals. Read the Supplement Facts panel and any proprietary blend listing.

^{26 17}

Can a greens powder replace vegetables?

No study we read shows that it can. The strong evidence is for whole fruit and vegetables eaten as food, and it is observational. The NHS advice counts produce by portions of 80 g and does not mention powders.

^{20 2}

Does a scoop count as a portion of vegetables?

We found no source saying so. The NHS 5 A Day portion is 80 g of fruit or vegetables, and its page does not mention powders.

²⁰

What have trials of greens powders found?

Very little. One 4-week trial of 30 healthy adults found no harm to digestion or blood tests and no clear benefit, and its authors included employees of the maker. A 6-month trial of fruit, vegetable and berry capsules gave early signals in a small open-label group.

^{5 16}

Do greens powders help gut health?

Not shown. In the one trial, digestive quality of life did not get worse, and an upward trend was not statistically significant. Two probiotic species rose in stool tests, probably from the product itself. A wheatgrass review found no direct studies on gut bacteria.

^{5 1}

Do greens powders boost energy, help weight loss or detox the body?

We found no trials showing that. These are marketing claims.

²⁵

Are greens powders safe with warfarin?

Ask your warfarin clinic first. The NHS says foods high in vitamin K, such as broccoli, spinach and other green leafy vegetables, can affect how warfarin works. A powder made from leafy vegetables could change your vitamin K intake.

^{23 15}

Are the algae ingredients, like spirulina and chlorella, safe?

Lab surveys found problems in some products: cyanotoxins above tolerable daily intake values in 8 of 18 products, microcystins in all 5 retail spirulina products tested, and drug residues in 52 spirulina and chlorella products that otherwise met EU metal limits. These are small surveys, not a verdict on every product.

^{12 10 13}

Can kelp in a greens powder affect the thyroid?

It can add iodine. The NHS says high doses of iodine over long periods could change how the thyroid works, and one case report describes a temporary overactive thyroid after kelp tablets. Ask a doctor if you have a thyroid condition.

^{21 3}

Is green tea extract in a blend a liver risk?

NCCIH says liver injury is uncommon but reported, mainly with green tea extracts in tablet or capsule form. Check whether your powder lists green tea extract.

^{18 7}

What does 'proprietary blend' mean?

The label gives the blend's name and total weight and lists its ingredients in order of weight, but not the amount of each. You cannot tell from the list how much of any one ingredient is inside.

¹⁷

Are greens powders safe in pregnancy or for children?

No safety study in pregnancy or children was found. NCCIH says many supplements have not been tested in pregnant women, nursing mothers or children, so ask a doctor or pharmacist first.

¹⁹

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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 greens powder summary, then re-read PubMed abstracts for every review, trial, case report and lab study cited, and read the NHS, NCCIH and FDA pages named. Only abstracts were read for papers. NIH Office of Dietary Supplements pages could not be read and are marked unverified.
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. The one finished-powder trial and the capsule trial were linked to the makers; this is flagged where the records show it.

Sources 26

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

Alva R, Shenoy D, Shetty V. From Chlorophyll to Micro Biome: Wheatgrass's Role in Gut Health-A Comprehensive Review.. Int J Prev Med. 2026. PMID 42921282. DOI 10.4103/ijpvm.ijpvm_320_25. (abstract)
Aune D, Giovannucci E, Boffetta P, Fadnes LT, Keum N, Norat T, et al.. Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality-a systematic review and dose-response meta-analysis of prospective studies.. Int J Epidemiol. 2017. PMID 28338764. DOI 10.1093/ije/dyw319. (abstract)
Gherbon A, Frandes M, Lungeanu D, Nicula M, Timar R. Transient Hyperthyroidism following the ingestion of complementary medications containing kelp seaweed: A case-report.. Medicine (Baltimore). 2019. PMID 31517826. DOI 10.1097/MD.0000000000017058. (abstract)
Kejžar J, Jagodic Hudobivnik M, Nečemer M, Ogrinc N, Masten Rutar J, Poklar Ulrih N. Characterization of Algae Dietary Supplements Using Antioxidative Potential, Elemental Composition, and Stable Isotopes Approach.. Front Nutr. 2020. PMID 33614692. DOI 10.3389/fnut.2020.618503. (abstract)
La Monica MB, Raub B, Hartshorn S, Gustat AL, Grdic J, Kirby TO, et al.. The effects of AG1® supplementation on the gut microbiome of healthy adults: a randomized, double-blind, placebo-controlled clinical trial.. J Int Soc Sports Nutr. 2024. PMID 39352252. DOI 10.1080/15502783.2024.2409682. (abstract)
Lorenzoni G, Minto C, Vecchio MG, Zec S, Paolin I, Lamprecht M, Mestroni L, Gregori D. Fruit and Vegetable Concentrate Supplementation and Cardiovascular Health: A Systematic Review from a Public Health Perspective.. J Clin Med. 2019. PMID 31717327. DOI 10.3390/jcm8111914. (abstract)
Navarro VJ, Khan I, Björnsson E, Seeff LB, Serrano J, Hoofnagle JH. Liver injury from herbal and dietary supplements.. Hepatology. 2017. PMID 27677775. DOI 10.1002/hep.28813. (abstract)
Pinto-Leite M, Martins D, Ferreira AC, Silva C, Trindade F, Saraiva F, et al.. The Role of Chlorella and Spirulina as Adjuvants of Cardiovascular Risk Factor Control: A Systematic Review and Meta-Analysis of Randomised Controlled Trials.. Nutrients. 2025. PMID 40289965. DOI 10.3390/nu17060943. (abstract)
Rajput S, Jain S, Mandal N, Mehrotra A, Pandey VK, Upadhyay CP, Koiri RK. Health risks of cyanotoxin contamination in dietary supplements: Mechanistic insights into organ-specific toxicity.. Food Chem Toxicol. 2026. PMID 42874982. DOI 10.1016/j.fct.2026.116449. (abstract)
Rhoades J, Fotiadou S, Paschalidou G, Papadimitriou T, Ordóñez AÁ, Kormas K, Vardaka E, Likotrafiti E. Microbiota and Cyanotoxin Content of Retail Spirulina Supplements and Spirulina Supplemented Foods.. Microorganisms. 2023. PMID 37317149. DOI 10.3390/microorganisms11051175. (abstract)
Roll S, Nocon M, Willich SN. Reduction of common cold symptoms by encapsulated juice powder concentrate of fruits and vegetables: a randomised, double-blind, placebo-controlled trial.. Br J Nutr. 2011. PMID 20727236. DOI 10.1017/S000711451000317X. (abstract)
Roy-Lachapelle A, Solliec M, Bouchard MF, Sauvé S. Detection of Cyanotoxins in Algae Dietary Supplements.. Toxins (Basel). 2017. PMID 28245621. DOI 10.3390/toxins9030076. (abstract)
Sochacka M, Kózka B, Kurek E, Giebułtowicz J. Spirulina and Chlorella Dietary Supplements-Are They a Source Solely of Valuable Nutrients?. Int J Mol Sci. 2025. PMID 41226507. DOI 10.3390/ijms262110468. (abstract)
Vankawala J, Altweiss E, Glaeser AM. Over-the-Counter Supplement Overuse: A Rare Potential Cause of Arsenic Poisoning and Bradycardia.. Cureus. 2025. PMID 41510484. DOI 10.7759/cureus.98745. (abstract)
Violi F, Lip GY, Pignatelli P, Pastori D. Interaction Between Dietary Vitamin K Intake and Anticoagulation by Vitamin K Antagonists: Is It Really True?: A Systematic Review.. Medicine (Baltimore). 2016. PMID 26962786. DOI 10.1097/MD.0000000000002895. (abstract)
Ziegler T, Darko A, Ledinski G, Kager G, Hörl G, Seemann A, Cvirn G, Lamprecht M. Effects of a Commercial Fruit, Vegetable and Berry Juice Powder Concentrate on Metabolic Safety and Cardiovascular Health in Older Adults: 6-Month Results of a Randomized Controlled Trial.. Nutrients. 2026. PMID 42738920. DOI 10.3390/nu18172746. (abstract)
. FDA: Dietary Supplement Labeling Guide, Chapter IV, Nutrition Labeling. . . (full-text)
. NCCIH: Green Tea (last updated February 2025). . . (full-text)
. NCCIH: Using Dietary Supplements Wisely (last updated January 2019). . . (full-text)
. NHS: Why 5 A Day? (page last reviewed 2026-09-30). . . (full-text)
. NHS: Iodine (page last reviewed 2020-08-03). . . (full-text)
. NHS: Vitamin K (page last reviewed 2020-08-03). . . (full-text)
. NHS: Warfarin (page last reviewed 2026-02-24). . . (full-text)
. NIH Office of Dietary Supplements: fact sheets (vitamin K, iodine). . . (not-read)
. PubMed searches run 2026-10-26 (search log, not a paper). . . (search-only)
. Existing AlternativeMed greens powder summary (read 2026-10-26). . . (summary-only)

Where to buy

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

The amount of the active ingredient per serving, not just the front-label claim
A third-party testing mark (USP, NSF or ConsumerLab)
Other ingredients and allergens
Ask a pharmacist about interactions with your medicines

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.