What Is Chlorella? Trials, Amounts Taken and Who Should Ask First

Chlorella is a single-celled green alga grown in fresh water, dried and sold as powder and tablets, usually Chlorella vulgaris or Chlorella pyrenoidosa; its human trials run one to 24 weeks in groups of 8 to 80 people, and across two 2026 poolings of 24 and 33 trials people taking it finished about 1.3 to 1.5 kg lighter and with LDL cholesterol about 6 mg/dL lower than controls, with the certainty rated moderate for LDL and low to very low for most other outcomes.^{1, 2} No health claim for chlorella is authorised in Great Britain, so a label may describe it but not say what it does.⁴ This page is part of the Wellgard electrolyte guide.

Sources checked on 3 November 2026.

Evidence at a glance

• Null trials: 84 adults with type 2 diabetes on 1.5 g a day for 8 weeks, no change in any measure; 40 adults with constipation on 6 g a day for 4 weeks, no change in stool frequency or blood folate.^{5, 6}
• Minerals: in a 14-day trial of 15 g a day in 80 healthy adults, ferritin fell from 38.0 to 20.2 micrograms per litre in the chlorella group, with plasma iron and selenium lower too.⁷
• Safety: a lactation monograph lists nausea, diarrhoea, cramping, flatulence, green stools, allergic reactions and photosensitivity, and says its vitamin K "may decrease warfarin effectiveness", the subject of a 1995 case report.^{8, 9}

What is chlorella, and which species is in supplements?

Chlorella is a microalga, "a unicellular green alga that grows in fresh water", dried and milled.^{8, 10} Its cell wall is tough enough to limit digestion: the 2023 feeding study below names it as a brake on how much of its iron and selenium the body takes up, and UK powders are sold labelled "cracked cell wall".^{7, 34} The trials and product surveys name Chlorella vulgaris, Chlorella pyrenoidosa and, less often, Chlorella regularis; a 2021 analysis of 15 commercial microalgae powders found the nutrient profiles "differ strongly between and within species", so one powder is not a stand-in for another.^{2, 11} It is eaten by the teaspoon, so it is not a protein source per serving; vegan protein sources has the arithmetic.

What did the human trials of chlorella measure?

Blood lipids, blood pressure, glucose, body weight, immune and antioxidant markers and, in a few, exercise. The 2026 pooling of 24 trials in 815 people, with no funding stated and one author declaring an editorial position, found body fat 0.73 points lower, weight 1.28 kg lower and LDL cholesterol 6.20 mg/dL lower than control, and rates the BMI evidence low certainty and most other outcomes very low, because "almost all of the 24 trials were judged to be of poor quality"; the companion 33-trial pooling, with an overlapping author team, reaches moderate certainty for LDL, total cholesterol and BMI.^{1, 2} An earlier pooling of 19 randomised trials in 797 people found systolic blood pressure 4.51 mmHg lower, and a 2022 pooling of 10 trials in 539 adults found LDL 7.71 mg/dL lower and notes that only two of the ten had checked the chlorella content, purity or contamination of what they gave.^{3, 12}

The single trials are listed with their dose, length and funder, because the funder matters here: several were paid for or supplied by chlorella makers.

The 15 g trial cuts the other way on minerals: the smoothie supplied 15.9 mg of iron a day, yet ferritin, plasma iron and selenium fell within the chlorella group, which the authors suggest may reflect the cell wall and the polysaccharides and flavonoids that lower iron and selenium uptake; the changes were not compared between groups.⁷

How much chlorella did the trials use, and what does a label say?

The trials in the table ran from 200 mg to 15 g a day and from 2 days to 8 weeks, most of them 1.2 to 6.3 g a day for four to eight weeks; the 33-trial pooling spans 135 mg to 15 g a day and 1 to 24 weeks, in groups of 8 to 80 people.² The two dose analyses disagree: the 2018 pooling finds the lipid and blood-pressure effects in trials of 8 weeks or longer at more than 4 g a day, the 2022 pooling finds the LDL effect at up to 1,500 mg a day and not above.^{3, 12} A label states its own amount per serving: in a 2022 Belgian survey the chlorella tablets were 400 or 500 mg each with directions from 1 to 12 a day, and the powders by the spoonful where a direction was given.²² Read the amount against the trial you are interested in rather than against "chlorella" in general: a 400 mg tablet and a 6 g dose are different experiments.

What are the side effects of chlorella?

The US Drugs and Lactation Database monograph says chlorella is usually well tolerated but can cause nausea, diarrhoea, abdominal cramping, flatulence and green stools; that allergic reactions, including asthma and anaphylaxis, have been reported in people taking it and in people making the tablets; and that photosensitivity reactions have occurred.⁸ The trials add frequencies: in the 2003 vaccine trial fatigue was reported by 44% of the 41 people on 200 mg against 19% of the 42 on placebo and 20% of the 40 on 400 mg; the 8-week 5 g trial recorded no serious adverse reaction; the 14-day 15 g trial raised blood and urine uric acid.^{7, 13, 15} In a survey of 150 Polish consumers of microalgae supplements, diarrhoea, nausea, abdominal pain and skin rash were among the adverse events most often reported.²³

One caution comes from the immune trials themselves. A 2025 scoping review of 469 studies lists chlorella and spirulina among the 15 herbal supplements with the strongest evidence of stimulating the immune system, and was written to help clinicians advise people with autoimmune skin disease; the 2025 letter that gathered the published cases found five, three of dermatomyositis and two of pemphigus, all beginning after spirulina; its search did not cover chlorella.^{24, 25} Anyone with an autoimmune condition or on an immunosuppressant asks their specialist before adding either.

Can you take chlorella with warfarin?

Not without telling your anticoagulant clinic. Warfarin works by blocking vitamin K, and the monograph says "The high vitamin K content of Chlorella may decrease warfarin effectiveness."⁸ The one published case is from 1995: a 75-year-old man with atrial fibrillation, whose warfarin had been well controlled, had his clotting test rise above the therapeutic limit after he started chlorella, with no missed warfarin, vitamin K medicine or natto found.⁹ No analysis in the sources gives a vitamin K figure per tablet or gram, so the amount cannot be counted into a diet the way spinach or broccoli can.^{8, 9} The NHS warfarin page says "Talk to your doctor before making any big changes to your diet when taking warfarin" and that you should not take vitamin K supplements while taking warfarin, that foods high in vitamin K "can affect how warfarin works" and to "talk to your warfarin clinic for advice", and "Before taking warfarin, tell your doctor if you're taking any other medicines, herbal remedies, vitamins or supplements."²⁶ Its anticoagulants page says to "Speak to your GP, anticoagulant clinic or pharmacist before taking any other medicines".²⁷ Never stop or change warfarin on your own account: the NHS says "Do not stop taking warfarin unless your doctor tells you to."²⁶ The vitamin K rules are on what foods are high in vitamin K2.

Is chlorella safe in pregnancy and breastfeeding?

Ask first. The NHS pregnancy page says "If you need higher dose folic acid or other supplements, speak to a GP", and the UK consumer guidance on food supplements says to "Check with your GP or healthcare professional before taking a food supplement if you are pregnant, breastfeeding, have any medical conditions or are taking any regular prescribed medication."^{28, 29} The studies that exist are small and Japanese, and in the 2024 trial the tablets came from the maker, two of whose employees are authors. In a 2024 open-label trial, 22 pregnant women with raised C-reactive protein were allocated by the month of their clinic visit, which the authors call random, to 6 g a day (30 tablets) from 12 to 18 weeks until delivery or to no supplement; none of the 10 on chlorella were constipated against 8 of the 12 controls.³⁰ A 2010 non-randomised study gave 32 of 70 women the same 6 g and found fewer with haemoglobin below 11 g/dL and less proteinuria and oedema in the third trimester; two smaller studies measured breast milk, finding lower dioxin toxic equivalents and more immunoglobulin A in 18 of 35 women, and 2.6 times the lutein in 10 women against 10 controls; no funding is stated on their records.^{31, 32, 33} The monograph judges maternal chlorella "probably acceptable during breastfeeding" and notes that green breast milk has been reported.⁸ None of these studies was large enough to find harm, and only the 2024 trial, in 10 women, set out to look for it; they show what was measured, not safety.

Does chlorella contain iodine?

Very little. In a 2024 analysis of 23 algae bought in the UK, the two chlorella powders held 2.2 and 3.2 mg of iodine per kilogram, the two spirulina powders 1.1 and 1.6, and the seaweeds an average of about 1,900 mg/kg; a 3 g serving of chlorella is therefore about 7 to 10 micrograms against the 140 micrograms a day the NHS says adults need, and the 15 g smoothie in the 2023 trial supplied 33.8 micrograms.^{7, 34, 35} A greens powder that adds kelp or another seaweed is answered on what sea moss is and why its iodine varies and thyroid supplements.

Heavy metals and cyanotoxins: what the surveys found and the GB limits

Chlorella takes up what is in its water, so the surveys matter more than the species. In a 2025 analysis of 52 spirulina and chlorella products, 29 conventional and 23 organic, every sample was within the EU limits for toxic metals and the two kinds did not differ; the authors flag aluminium against its tolerable weekly intake and the pharmaceutical residues they found, caffeine most often.³⁶ In a 2020 Spanish analysis of 10 microalgae supplements, lead was high in some, and microcystin-LR and anatoxin-a, toxins made by cyanobacteria, were found in 3, including one chlorella product at a level too low to quantify.³⁷ In Belgium, 9 of 35 algal supplements contained microcystins and 3 exceeded 1 microgram per gram, a proposed guideline rather than a GB legal limit, but eight of the nine were wholly Aphanizomenon flos-aquae, the ninth a mix of spirulina, chlorella and Aphanizomenon with one microcystin detected below the quantification limit, and every chlorella-only product was below detection; in China 7 of 19 contained microcystins and 2 exceeded that level, and in the United States some of 18 held more than 40 times it.^{22, 38, 39} The limits for a food supplement sold in Great Britain, as sold, are lead 3.0 mg/kg, cadmium 1.0 mg/kg and mercury 0.1 mg/kg; a certificate of analysis for the batch answers the question for a given tub.⁴⁰

Does chlorella detox the body or remove heavy metals?

No human trial has tested chlorella against heavy metals, and the claim is not allowed. The Advertising Standards Authority's advice is that the liver and kidneys detoxify and excrete many toxic materials on their own, that it "has not seen evidence to support the theory that toxins can be removed from the body by other means", and that "general detox claims made in relation to a food product are likely to be considered health claims", which need an authorised wording; none exists.⁴¹ A claim to remove heavy metals goes further: the UK consumer guidance says supplements "should not be sold with claims that they can prevent, treat or cure a medical condition", because "this is the function of medicines, and is an offence."²⁹ The human studies of a pollutant are two non-randomised Japanese breast-milk dioxin studies, in 23 and 18 women, and two two-week randomised crossover trials in 6 and 12 Korean women that measured urinary traces of cooked-meat and smoke carcinogens, with changes that did not reach significance; a PubMed search on 3 November 2026 found no randomised trial of chlorella and heavy-metal removal in people, and a 2015 review found no randomised trial of any commercial detox programme either.^{32, 42, 43, 44, 45}

What can a chlorella label say?

What it is and how much is in it. The GB nutrition and health claims register holds no entry for chlorella or spirulina, so no sentence about immunity, energy, detox or anything else is authorised for it, and the register's two chlorophyll entries, including one for "daily detoxification support", are non-authorised.⁴ Several chlorella wordings sit on the Department of Health and Social Care's on-hold list of botanical claims, never assessed, so none is used here.⁴⁶ A product that also supplies a named vitamin or mineral at the amount the register requires may carry that nutrient's authorised wording; the wording belongs to the nutrient, not to the alga.⁴

What we don't know

• Whether any pooled effect lasts beyond 24 weeks: no trial ran longer.²
• Whether chlorella raises or lowers iron status at label amounts: the 15 g trial lowered ferritin within the group over 14 days, the 2025 review of seven human and 25 animal studies reports the opposite.^{7, 21}
• Whether chlorella removes any pollutant from the body: the four small human studies measured dioxins in breast milk and urinary traces of two carcinogen groups, and none tested a heavy metal.^{32, 42, 43, 44}

Frequently asked questions

Is chlorella the same as spirulina?

No. Spirulina is a cyanobacterium, Arthrospira platensis, and chlorella is a green alga with a thick cell wall; both grow in fresh water and both hold little iodine.^{7, 10, 34} They part on vitamin B12, below, and on contaminants and immune case reports, above.^{22, 25}

Is chlorella the same as chlorophyll?

No. Chlorophyll is the green pigment; chlorella is the whole organism, and its powders are about 1.8 to 1.9 g of chlorophyll per 100 g.¹¹

Does chlorella contain vitamin B12?

Some, in a form that may or may not be usable. A 2002 analysis found true vitamin B12 the main form in chlorella tablets and the inactive pseudo-B12 the main form in spirulina tablets, but in the 2021 analysis of 15 commercial powders cobalamin was below 20 micrograms per 100 g in every one, the chlorella powders included, against label figures of 60 and 300 micrograms on two of the chlorella powders, which the authors suggest may be pseudo-cobalamin.^{11, 47} In the 15 g a day trial serum B12 rose within the chlorella group over 14 days, with no difference between groups.⁷ On a vegan diet the NHS says "a vitamin B12 supplement may be needed"; see foods high in vitamin B12.⁴⁸

How do you report a reaction to a supplement?

The UK consumer guidance says: "If you are concerned about the safety, labelling or claims made by a food supplement, you should report the issue to your Local Authority or District Council", which passes food safety incidents to the Food Standards Agency.²⁹ A reaction that needs treatment goes to a GP or NHS 111 first.

Sources

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2. Jafari A, et al. Chlorella for health: evidence from a GRADE-assessed systematic review and dose-response meta-analysis. Systematic Reviews, 2026. 33 trials, 135 mg to 15 g a day, 1 to 24 weeks, 8 to 80 people each; weight -1.52 kg, body fat -0.72%, LDL -5.70 mg/dL, total cholesterol -7.02, HDL +1.57; moderate certainty for LDL, total cholesterol and BMI, low for body fat, weight, blood pressure, HDL and triglycerides, very low for the rest; no specific grant received; one author declares an editorial position. PubMed 42928353 (full text PMC13700261).
3. Fallah AA, et al. Effect of Chlorella supplementation on cardiovascular risk factors: a meta-analysis of randomized controlled trials. Clinical Nutrition, 2018. 19 randomised trials, 797 people; total cholesterol -9.09 mg/dL, LDL -8.32, systolic -4.51 mmHg, diastolic -1.64, fasting glucose -4.23; triglycerides, HDL and BMI not significant; effects in trials of 8 weeks or more above 4 g a day; funding not stated on the record. PubMed 29037431.
4. Department of Health and Social Care. GB nutrition and health claims register, last updated 19 May 2026. No entry for chlorella or spirulina; two chlorophyll entries (chlorophyll in sprouted seed; sodium copper chlorophyllin, "For daily detoxification support") non-authorised. Read 3 November 2026. gov.uk.
5. Hosseini AM, et al. The effects of Chlorella supplementation on glycemic control, lipid profile and anthropometric measures on patients with type 2 diabetes mellitus. European Journal of Nutrition, 2021. Randomised double-blind trial, 84 adults, 1,500 mg of Chlorella vulgaris a day, 8 weeks; no variable changed; funding not stated on the record. PubMed 33532874.
6. Nishimoto Y, et al. The nutritional efficacy of Chlorella supplementation depends on the individual gut environment: a randomised control study. Frontiers in Nutrition, 2021. Randomised double-blind crossover trial, 40 Japanese adults with constipation, 3 g of Chlorella pyrenoidosa tablets twice a day for 4 weeks against placebo; no difference in defecation frequency or blood folate; funded by a chlorella maker and a genomics company, six authors employed by the genomics company and one by the maker. PubMed 34136514 (full text PMC8200412).
7. Sandgruber F, et al. Impact of regular intake of microalgae on nutrient supply and cardiovascular risk factors: results from the NovAL intervention study. Nutrients, 2023. Randomised four-group trial, 80 healthy adults, 15 g of Chlorella pyrenoidosa dry weight in a daily smoothie, 14 days; within the chlorella group ferritin 38.0 to 20.2 micrograms/L, plasma iron 21.5 to 16.8 micromol/L, selenium 1.48 to 1.35 micromol/L, serum B12 higher, total and LDL cholesterol lower, uric acid higher; the smoothie supplied 15.9 mg iron, 1.65 micrograms selenium and 33.8 micrograms iodine; German Federal Ministry of Education and Research; no conflicts declared. PubMed 37049486 (full text PMC10097350).
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9. Ohkawa S, et al. Warfarin therapy and chlorella. Rinsho Shinkeigaku, 1995. Case report, one 75-year-old man; thrombotest values rose above the therapeutic limit after chlorella intake with no other cause found; Japanese with English abstract. PubMed 8777808.
10. Otsuki T, et al. Salivary secretory immunoglobulin A secretion increases after 4-weeks ingestion of chlorella-derived multicomponent supplement in humans: a randomized cross over study. Nutrition Journal, 2011. Randomised crossover trial, 15 men, 30 tablets of 200 mg a day, 4 weeks, 12-week washout; salivary IgA higher than baseline on chlorella (p < 0.01), unchanged on placebo; chlorella described as "a unicellular green alga that grows in fresh water"; the full text states that a chlorella company funded the study and supplied the tablets and that the first author has received a speaker's honorarium from it. PubMed 21906314 (full text PMC3182968).
11. Sandgruber F, et al. Variability in macro- and micronutrients of 15 commercially available microalgae powders. Marine Drugs, 2021. Laboratory analysis of 15 powders including Chlorella pyrenoidosa and vulgaris; cobalamin below 20 micrograms per 100 g in all; chlorophyll 1.8 to 1.9 g per 100 g in the chlorella powders; German Federal Ministry of Education and Research; no conflicts declared. PubMed 34071995 (full text PMC8228358).
12. Sherafati N, et al. Effect of supplementation with Chlorella vulgaris on lipid profile in adults: a systematic review and dose-response meta-analysis of randomized controlled trials. Complementary Therapies in Medicine, 2022. 10 trials, 539 adults; total cholesterol -7.47 mg/dL, LDL -7.71; LDL effect at 0 to 1,500 mg a day; only two trials characterised the product; funding not stated on the record. PubMed 35331862.
13. Halperin SA, et al. Safety and immunoenhancing effect of a Chlorella-derived dietary supplement in healthy adults undergoing influenza vaccination: randomized, double-blind, placebo-controlled trial. CMAJ, 2003. 124 adults aged 50 and over, 200 or 400 mg a day, 28 days; no difference in antibody response overall; fatigue 18 of 41 (44%) on 200 mg, 8 of 40 (20%) on 400 mg, 8 of 42 (19%) on placebo; research support from a source other than the US government on the record. PubMed 12874157.
14. Lee SH, et al. Six-week supplementation with Chlorella has favorable impact on antioxidant status in Korean male smokers. Nutrition, 2010. Randomised double-blind trial, 52 smokers, 6.3 g a day, 6 weeks; plasma vitamin C +44.4%, alpha-tocopherol +15.7%; lymphocyte DNA damage fell on placebo as well; research support from a source other than the US government on the record. PubMed 19660910.
15. Kwak JH, et al. Beneficial immunostimulatory effect of short-term Chlorella supplementation: enhancement of natural killer cell activity and early inflammatory response. Nutrition Journal, 2012. Randomised double-blind trial, 51 adults (23 chlorella, 28 placebo), 5 g a day, 8 weeks; NK activity, interferon-gamma and interleukin-1beta rose against placebo; no serious adverse reactions; funded by the Korean national research foundation, a health ministry programme and a corporation (full text). PubMed 22849818 (full text PMC3511195).
16. Ryu NH, et al. Impact of daily Chlorella consumption on serum lipid and carotenoid profiles in mildly hypercholesterolemic adults: a double-blinded, randomized, placebo-controlled study. Nutrition Journal, 2014. 63 adults, 5 g a day, 4 weeks; total cholesterol -1.6% against +0.03%, triglycerides -10.3% against +11.9%; supported by a corporation and two Korean ministries, with no funder involvement in design, analysis or writing (full text). PubMed 24920270 (full text PMC4066283).
17. Kim S, et al. A dietary cholesterol challenge study to assess Chlorella supplementation in maintaining healthy lipid levels in adults: a double-blinded, randomized, placebo-controlled study. Nutrition Journal, 2016. 34 adults, 5 g a day with 510 mg of cholesterol from three eggs, 4 weeks; total cholesterol rose 3.5% against 9.8%, LDL 1.7% against 14.3%; unrestricted grant from a corporation and a Korean ministry, funders not involved (full text). PubMed 27177615 (full text PMC4866071).
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19. Okada H, et al. Effect of Chlorella ingestion on oxidative stress and fatigue symptoms in healthy men. Kurume Medical Journal, 2018. Randomised double-blind trial, 27 men, 6 g a day, 4 weeks; resting antioxidant capacity rose on chlorella; no difference in oxidative stress indices under exercise; funding not stated on the record. PubMed 29780062.
20. White H, et al. Chlorella supplementation reduces blood lactate concentration and increases O2 pulse during submaximal and maximal cycling in young healthy adults. Nutrients, 2024. Randomised double-blind crossover trial, 20 adults, 6 g a day, 2 days; submaximal lactate 2.67 against 3.05 mmol/L; VO2max unchanged; no external funding, no conflicts declared. PubMed 38474825.
21. Lacurezeanu A, et al. Arthrospira platensis and Chlorella vulgaris consumption on iron status: a systematic review of in vivo studies. Molecular Nutrition and Food Research, 2025. Narrative systematic review, 32 studies (7 human, 25 animal); haemoglobin and ferritin reported higher; Romanian research grant; no conflicts declared. PubMed 41255135.
22. Van Hassel WHR, et al. LC-MS/MS validation and quantification of cyanotoxins in algal food supplements from the Belgium market and their molecular origins. Toxins, 2022. 35 supplements; microcystins in 9, 3 above 1 microgram per gram, a proposed guideline value; every contaminated product 100% Aphanizomenon flos-aquae except one mix with chlorella below quantification; chlorella tablets of 400 or 500 mg with directions of 1 to 12 a day (full-text table); Belgian food safety agency; no conflicts declared. PubMed 36006175 (full text PMC9415669).
23. Rzymski P, et al. Microalgal food supplements from the perspective of Polish consumers: patterns of use, adverse events, and beneficial effects. Journal of Applied Phycology, 2017. Online survey, 150 consumers of spirulina, chlorella and Aphanizomenon; self-reported adverse events, not incidence; funded by a Foundation for Polish Science grant (full text). PubMed 28775657.
24. Weiner JD, et al. Identifying immunostimulatory herbal supplements that may flare autoimmune skin diseases: a systematic scoping review. Lupus Science and Medicine, 2025. 469 studies, 227 herbal supplements; 15 with the strongest evidence including chlorella and spirulina; US National Institutes of Health support; no competing interests. PubMed 41475897.
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26. NHS. Warfarin. Page last reviewed 24 February 2026. Big changes to diet, no vitamin K supplements, foods high in vitamin K and the warfarin clinic, telling your doctor about supplements, not stopping warfarin. nhs.uk/medicines/warfarin.
27. NHS. Anticoagulant medicines. Page last reviewed 9 September 2024. Speak to your GP, anticoagulant clinic or pharmacist before taking any other medicines. nhs.uk/conditions/anticoagulants.
28. NHS. Pregnancy vitamins and supplements. Page last reviewed 3 June 2026. "If you need higher dose folic acid or other supplements, speak to a GP." nhs.uk/pregnancy/keeping-well/pregnancy-vitamins-and-supplements.
29. Food Standards Agency and Department of Health and Social Care. Food supplements: guidance for consumers. Published 25 June 2026. Checking with a GP in pregnancy, breastfeeding or on regular medicines; claims to prevent, treat or cure as the function of medicines; reporting to the local authority. gov.uk.
30. Uchiyama-Tanaka Y, et al. The effect of Chlorella supplementation in pregnant women with low-grade inflammation. Food Science and Nutrition, 2024. Open-label controlled trial, 22 women allocated by month of clinic visit (described as random), 6 g a day (30 tablets) from 12 to 18 weeks of pregnancy until delivery; constipation in 0 of 10 against 8 of 12; no funding; two authors employees of the tablet maker, which supplied the tablets free (full text). PubMed 38268875 (full text PMC10804112).
31. Nakano S, et al. Chlorella pyrenoidosa supplementation reduces the risk of anemia, proteinuria and edema in pregnant women. Plant Foods for Human Nutrition, 2010. Controlled non-randomised study, 70 women (32 chlorella, 38 control), 6 g a day from 12 to 18 weeks until delivery; funding not stated on the record. PubMed 20013055.
32. Nakano S, et al. Chlorella (Chlorella pyrenoidosa) supplementation decreases dioxin and increases immunoglobulin A concentrations in breast milk. Journal of Medicinal Food, 2007. Controlled study, 35 women of whom 18 took chlorella tablets in pregnancy; dioxin toxic equivalents lower (p = 0.003), IgA higher (p = 0.03); funding not stated on the record. PubMed 17472477.
33. Nagayama J, et al. Effect of maternal Chlorella supplementation on carotenoid concentration in breast milk at early lactation. International Journal of Food Sciences and Nutrition, 2014. Controlled study, 20 women, 6 g a day from week 16 to 20 until delivery; lutein 2.6-fold, zeaxanthin 2.7-fold, beta-carotene 1.7-fold higher; funding not stated on the record. PubMed 24635025.
34. Casas-Agustench P, et al. Nitrate, nitrite, and iodine concentrations in commercial edible algae: an observational study. Foods, 2024. Laboratory analysis of 23 algae bought in the UK; microalgae iodine 17.61 mg/kg on average against 1,925 mg/kg for seaweeds; chlorella 2.20 and 3.17 mg/kg, spirulina 1.07 and 1.63 mg/kg (Table 2); University of Plymouth; no conflicts declared. PubMed 39200542 (full text PMC11353717).
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37. Sánchez-Parra E, et al. Are cyanotoxins the only toxic compound potentially present in microalgae supplements? Toxins, 2020. 10 supplements; microcystin-LR and anatoxin-a in 3, including one chlorella product below the quantification limit; high lead in some; University of Murcia; no conflicts declared. PubMed 32872271 (full text PMC7551278).
38. Liu T, et al. Simultaneous determination of twelve microcystins in algal supplements on the Chinese market and possible risks to exposed populations. Food Additives and Contaminants: Part A, 2025. 19 products; 7 contained microcystins, 2 above 1 microgram per gram; funding not stated on the record. PubMed 39761342.
39. Miller TR, et al. Microcystin toxins at potentially hazardous levels in algal dietary supplements revealed by a combination of bioassay, immunoassay, and mass spectrometric methods. Journal of Agricultural and Food Chemistry, 2020. 18 supplements; some above 40 times the 1 microgram per gram level by LC-MS/MS; funding not stated on the record. PubMed 32597644.
40. Regulation (EC) No 1881/2006 as it applies in Great Britain, Annex: maximum levels for contaminants in food supplements, lead 3.0 mg/kg (3.1.22), cadmium 1.0 mg/kg (3.2.21), mercury 0.1 mg/kg (3.3.3). Read 3 November 2026. legislation.gov.uk.
41. Committee of Advertising Practice and Advertising Standards Authority. Detoxing: general. AdviceOnline, 25 October 2022. The liver and kidneys, no evidence for removal by other means, detox claims on foods as health claims. asa.org.uk.
42. Nakano S, et al. Maternal-fetal distribution and transfer of dioxins in pregnant women in Japan, and attempts to reduce maternal transfer with Chlorella (Chlorella pyrenoidosa) supplements. Chemosphere, 2005. Non-randomised study, 44 pregnant Japanese women of whom 23 were instructed to take Chlorella pyrenoidosa tablets in pregnancy; dioxin toxic equivalents in breast milk about 30% lower in the chlorella group (p = 0.0113); funding not stated on the record. PubMed 15985279.
43. Lee I, et al. Detoxification of chlorella supplement on heterocyclic amines in Korean young adults. Environmental Toxicology and Pharmacology, 2015. Randomised double-blind placebo-controlled crossover trial, 6 women, 2 weeks; urinary MeIQx lower at borderline significance (0.05 < p < 0.1), PhIP and IQx-8-COOH unchanged; research support from a source other than the US government on the record, funder not named. PubMed 25590673.
44. Yang M, et al. Epigenetic modulation of Chlorella (Chlorella vulgaris) on exposure to polycyclic aromatic hydrocarbons. Environmental Toxicology and Pharmacology, 2015. Randomised double-blind crossover trial, 12 healthy women, four tablets three times a day, 2 weeks; urinary 1-hydroxypyrene lower (p < 0.1); research support from a source other than the US government on the record, funder not named. PubMed 26432772.
45. Klein AV, Kiat H. Detox diets for toxin elimination and weight management: a critical review of the evidence. Journal of Human Nutrition and Dietetics, 2015. "No randomised controlled trials have been conducted to assess the effectiveness of commercial detox diets in humans"; funding not stated on the record. PubMed 25522674.
46. Department of Health and Social Care. 'On hold' health claims on foods. Updated 12 January 2021. Chlorella wordings on hold, never assessed, not used here. gov.uk.
47. Watanabe F, et al. Characterization and bioavailability of vitamin B12-compounds from edible algae. Journal of Nutritional Science and Vitaminology, 2002. Review with analytical data; true B12 the predominant form in chlorella tablets, pseudovitamin B12 in spirulina tablets; funding not stated on the record. PubMed 12656203.
48. NHS. The vegan diet. Page last reviewed 5 June 2026. "Sources for vegans are limited and a vitamin B12 supplement may be needed." nhs.uk/live-well/eat-well/how-to-eat-a-balanced-diet/the-vegan-diet.

This article is general information, not medical advice. If you take warfarin or another anticoagulant, an immunosuppressant or any regular medicine, have an autoimmune condition, or are pregnant or breastfeeding, ask your GP, pharmacist, anticoagulant clinic or specialist before taking chlorella, and never stop or change a prescribed medicine on your own account.

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