We've released Evidence-based Keto: Your no-hype guide to the ketogenic diet, and sale ends tomorrow . Click here to learn more

Quick Navigation


Chlorella is a freshwater algae that is commonly supplemented by vegan populations (similar to Spirulina). Chlorella appears to be a bioavailable source of both Iron and Vitamin B12, and may have other benefits.

Our evidence-based analysis on chlorella features 39 unique references to scientific papers.

Research analysis led by .
Reviewed by
Examine.com Team
Last Updated:

Things To Know & Note

Primary Function:

Also Known As

Chlorella pyrenoidosa

How to Take Chlorella

Recommended dosage, active amounts, other details

Supplementation of chlorella appears to be in the range of 6-10g daily. It is unsure why this dose is chosen, but it appears to be somewhat effective. Higher doses have not been sufficiently tested and the optimal dose of supplemental chlorella is not known.


ON SALE UNTIL TOMORROW: Evidence-based Keto

Unbiased truth on keto and long-term effects on health, safety, pre-existing conditions, losing weight, and more.

Learn the latest on keto

Human Effect Matrix

The Human Effect Matrix looks at human studies (it excludes animal and in vitro studies) to tell you what effects chlorella has on your body, and how strong these effects are.
Grade Level of Evidence
Robust research conducted with repeated double-blind clinical trials
Multiple studies where at least two are double-blind and placebo controlled
Single double-blind study or multiple cohort studies
Uncontrolled or observational studies only
Level of Evidence
? The amount of high quality evidence. The more evidence, the more we can trust the results.
Outcome Magnitude of effect
? The direction and size of the supplement's impact on each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.
Consistency of research results
? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.
grade-c Minor - See study
No remarkable effects following oral ingestion of chlorella, although some may be present
grade-c Minor Moderate See all 3 studies
Might reduce blood pressure in some instances but does not appear remarkably potent.
grade-c Minor - See study
Increase in salivary IgA suggests an immune enhancing effect; no comparison to an active control.
grade-c - - See study
Has once failed to modify the DNA damage observed in male smokers
grade-c - - See study
No significant effects on fat mass
grade-c - - See study
No significant influence on heart rate has been detected
grade-c - - See study
Has once failed to act effectively as a vaccine adjuvant
grade-c - - See study
No significant effects on body weight
grade-d Minor - See study
Study in pregnant women, it did have efficacy but more studies are required to assess chlorella overall.
grade-d Minor - See study
Reduced proteinuria in pregnant women (possibly indiciative of kidney protective effects); more studies would be prudent as to include comparators or use in other contexts.
grade-d Minor - See study
May be secondary to the Iron content, somewhat effective in pregnant women. Requires more evidence, especially in anemics
grade-d Minor - See study
May have efficacy in reducing pain associated with fibromyalgia, but requires more evidence

Studies Excluded from Consideration

  • Excluded due to being highly confounded[1]

Everything you need to know about the keto diet

When we asked our users what they wanted us to cover, many of them mentioned the keto diet.

So we listened. We spent the year looking up the research on the ketogenic diet to help guide you in your journey.

With Evidence-based Keto, Examine.com gives you all the scientific research, but in understandable language with tons of informative infographics. No opinion, no bias, no conflict of interest.

If you’re interested in keto, this is a must-have unbiased source.

Scientific Research on Chlorella

Click on any below to expand the corresponding section. Click on to collapse it.

Click here to fully expand all sections or here to fully collapse them.

Chlorella is a unicellular fresh water algae, known for being a vegan source of both iron and bioavailable B12 (cobalamin), which is one of the few green algaes to possess a bioactive B12 form alongside porphyra yezoensis (Nori)[2][3] and pleurochrysis carterae.[4] Consuming these seaweed sources in the diet is associated with higher serum B12 concentrations in vegans when compared to vegans not consuming seaweed products.[5]

Chlorella (the genus) tends to contain the macronutrient profile of:

  • Lipids (Fatty Acids) at 12.0+/-0.56% dry weight at the low end, but sometimes estimated as high as 28-32% dry weight,[6] containing some saturated fatty acids (myristate, palmitate, laurate).[7] Lipids may be lost by over 70% during the process of pigment removal (bleaching) with activated clay[8]

  • Protein (chlorella pyrenoidosa) relatively high in leucine (7.3% total protein[9]) and glutamate (9% total protein[9])

Noncaloric micronutrients found in chlorella species include:

  • Chlorophyll at 1.3% dry weight of chlorella vulgaris[8]

  • Active Vitamin B12 at 205-223mcg/100g (Cobalamin) [10], unlike Spirulina which does not have active B12 but instead 7-adenyl cyanocobamide (pseudovitamin B12)[11]

Chlorella vulgaris tends to be sold as 'Broken Cell Wall' chlorella.

For the major purpose of chlorella supplementation, an apparent detoxification of heavy minerals, limited evidence in mice suggest that breaking the cell wall is not necessary.[12]

One in vitro study investigating the efficacy of chlorella in inhibiting the Breast Cancer Resistance Protein (BCRP), an efflux transporter whose inhibition may augment chemotherapy, found that Chlorella exerted moderate to weak inhibition at 22.4% of control at 1mg/mL; it was outperformed by Milk Thistle, rutin, and soybean extract at the same dosages while the active control of 5µM fumitremorgin was as effective as Soy and Rutin but outperformed all others.[13]

Among plants, chlorella vulgaris as a plant is able to bioaccumulate heavy metals (as assessed by hexavalent chromium) to a larger degree than its environment[14] which is a common property for algae in general[15] with chlorella vulgaris being noted to accumulate up to 3,579.01μg/g heavy metal in a medium containing 100μg/mL hexavalent chromium.[14] Other studies assessing the bioaccumulation properties of chlorella species have noted success with accumulating arsenic[16][17] and mercury.[18]

When looking in vitro, most algae appears to be able to accumulate metals from their surroundings to a large degree. Chlorella is implicated in this, being able to bioaccumulate heavy metals to a large degree

In mice, the chlorella source of parachlorella beijerinckii (CK-5 strain with walls intact) given to pregnant mice at 10% of the diet alongside intentional mercurcy contamination noted that the chlorella group was associated with mildly less mercurcy accumulation in the blood (15%) and brain (13.5%) of the mother with less in blood, brain, liver, and the kidney of the fetus after birth.[12] This enhancement of mercury removal from mice has been noted elsewhere at half the dose (5% of the diet) in as little as 21 days[19] and 100mg acutely (5,400mg/kg; estimated human equivalent of 430mg/kg) alongside a high dose of mercury (5mg/kg) has been noted to increase fecal and urinary mercury elimination in mice relative to control.[20]

High doses of a particular strain of chlorella known as parachlorella beijerinckii CK-5 appear to have mouse evidence for increasing mercury removal from the organism following oral ingestion. This requires feasible yet high oral doses, and it is not confirmed if this extends to chlorella vulgaris (the major supplemental form of chlorella)

Pregnancy is associated with Anemia in approximately 18% of women industrialized countries (not recent statistics)[21] although recently has been pinpointed at 17-22% in Japan.[22] It has previously been reported in rats that diets with chlorella (5-10%) were capable of increasing erythrocytic (red blood cell) iron content and aid the state of anemia[23] and these results were replicated in pregnant women given 6g of Chlorella from some time point between gestation weeks 12-18 until delivery, where Chlorella was associated with significantly higher Hemoglobin (+5.6%), Hematocrit (+6.3%), and Red Blood Cell count (+4.7%) compared to control (unblinded).[24] The amount of women remaining above a 11g/dL threshold for hemoglobin concentration was significantly enhanced with Chlorella, and no influence on blood pressure was noted.[24]

One study investigating a GABA rich Chlorella supplement (500mg/100g) in hypertensive persons (systolic 130-159mmHg) given 10g Chlorella delivering 20mg GABA noted that over 12 weeks Chlorella was associated with lower systolic and diastolic blood pressure from week 4 onward, with more potency in persons with higher blood pressure at baseline.[25] These results were building off a previous dose-response study in humans where the same GABA-rich Chlorella extract was associated with significant reductions in blood pressure in a hypertensive population.[25]

Other studies that make note of blood pressure changes note no significant effect on pregnant women using 6g Chlorella daily until delivery[24] and a lowering of systolic blood pressure in male smokers (6.3g Chlorella) that failed to reach statistical significance.[26]

After chronic oral consumption to rats, less astrocytic activation in the hippocampal CA1 region has been noted; indicative of antiinflammatory effects.[27]

One study in mice assessing cognition (via Morris Water-Maze) noted that Chlorella was ineffective in young rats regardless of mouse strain (DAL101 or C57BL/6) but suppressed the decline in memory (spatial and visual recognition) associated with premature aging in DAL101.[27]

A study in persons with signs of metabolic syndrome that measured genomic changes in response to supplementation of Chlorella noted variations in mRNA transcription involved in insulin signalling (such as the receptor itself and PTP1B) but did not precisely quantify these changes,[28] it appeared genes involved in insuling signalling and glucose uptake (GLUT4, Akt) were enhanced while supressive proteins (PTP1B) were suppressed within the range of 0.5-2.0fold basal activity, and these were said to possibly explain the small but statistically significane reduction in blood pressure seen with Chlorella.[28]

10g of Chlorella taken daily for 2 months was associated with a 22% decrease in pain (assessed by TPI) in one pilot study in 18 persons with Fibromyalgia.[29] This study required participants to have a Tender Point Index (TPI) of 22 or greater, and the average TPI of 32 at baseline decreased to 25 after 2 months and two patients noted more than 50% improvement[29] (study duplicated in Medline[30]).

One intervention using a crossover design noted that 4 weeks of Chlorella supplementation at 6g daily was able to increase salivary Immunoglobulin A concentrations,[31] suggesting it may play a role in protecting against respiratory tract infections due to IgA's importance[32] and significant inverse correlation to infection.[33][34] Interestingly, increased Immunoglobulin A has also been found in the breast milk of mothers consuming Chlorella during their pregnancy.[35]

One study has been conducted with 200 or 400mg Chlorella supplementation for a period of 3 weeks prior to undergoing vaccination and for 7 more days, and noted that Chlorella supplementation failed to augment the antibody response to vaccination.[36]

One study that had no control group, but used Chlorella (9g daily; two doses of 4.5g) in either healthy persons or obese persons with symptoms similar to metabolic syndrome over a period of 12 weeks (with 4 monitored weeks thereafter) noted that there was a statistically significant reduction in body fat at week 12 in both groups, which was attenuated by week 16; the decrease was not apparent at weeks 0-8.[28]

One study investigating the immune system but also measuring anthropometric measures noted that 4 weeks of supplementation of 6g chlorella to otherwise healthy non-obese adult men failed to modify either lean mass or fat mass.[31] This has also been noted with a higher dose (10g) of GABA-rich Chlorella over a period of 12 weeks.[25]

Interventions suggest either no effects, or clinically insignificant effects (small magnitude) that disappear with cessation; Chlorella is not apparently anti-obese or pro-fat loss

In vitro, Chlorella shows some ability to metabolize more potent estrogens (estradiol) to lesser potent forms such as estrone and an unknown metabolite; unknown if this can occur in vivo .[37] This biodegradation has been noted elsewhere[38] and may extend to other phenolic compounds with structural similarity like Bisphenol-A.[39]

Appears to be able to degrade estrogens and xenoestrogens outside of the body, but whether these abilities carry over into the body is unknown (and likely doubtful, as light sensitivity implicates enzymes that may be degraded after digestion)

One study in pregnant women noted that 6g of Chlorella was associated with less urinary proteins, suggesting a renoprotective effect; mechanisms unknown.[24]

One study conducted in moderate to heavy drinking Korean Smokers (tobacco) given 6.3g Chlorella daily for 6 weeks noted an increase in serum Vitamin C (44.4%) and Vitamin E (15.7%), as well as two antioxidant enzymes in red blood cells (catalase by 5.5% and superoxide dismutase by 17.5%).[26] Alpha and Beta-carotenes as well as red blood cell Glutathione Peroxidase did not change significantly, and this was thought to be secondary to preservation of systemic anti-oxidants from Chlorella's inherent anti-oxidant capabilities, although Chlorella itself has a Vitamin E content.[26] DNA damage measured in lymphocytes decreased in both Chlorella and placebo.

One study has been conducted on the environmental estrogen Dioxin noting an inverse relationship between oral Chlorella intake in mothers and reduced Dioxin concentration in breast milk; although Immunoglobulin A was higher in the breast milk of the Chlorella group, this was not associated with Dioxin.[35]

One human study has been conducted with 6g Chlorella during pregnancy from gestational week 12-18 (variable start date) until delivery, and was generally well tolerated with no reported adverse effects on mother or apparent adverse effects on offspring.[24]

Interestingly, toxicological reports indicate that Chlorella is associated with less leg edema (water retention and swelling) at 6g daily relative to control; with 44.7% of women in control reporting leg edema in the third trimester yet only 9.4% reporting edema with 6g Chlorella.[24] Some changes were apparent in the second trimester (6.3% v. 18.4%) but were not statistically significant.

Some human and animal interventions note green discoloration of feces due to the chlorophyll content of Chlorella, seen as benign and has been noted at 6g daily.[24] At this dose, loose stools and diarrhea are noted at times but are brief and clinically insignificant.[25]


  1. ^ Combined extractives of red yeast rice, bitter gourd, chlorella, soy protein, and licorice improve total cholesterol, low-density lipoprotein cholesterol, and triglyceride in subjects with metabolic syndrome.
  2. ^ Watanabe F, et al. Characterization of a vitamin B12 compound in the edible purple laver, Porphyra yezoensis. Biosci Biotechnol Biochem. (2000)
  3. ^ Takenaka S, et al. Feeding dried purple laver (nori) to vitamin B12-deficient rats significantly improves vitamin B12 status. Br J Nutr. (2001)
  4. ^ Miyamoto E, et al. Characterization of a vitamin B12 compound from unicellular coccolithophorid alga (Pleurochrysis carterae). J Agric Food Chem. (2001)
  5. ^ Rauma Al, et al. Vitamin B-12 status of long-term adherents of a strict uncooked vegan diet ("living food diet") is compromised.. J Nutr. (1995)
  6. ^ Biodiesel from microalgae.
  7. ^ Wawrik B, Harriman BH. Rapid, colorimetric quantification of lipid from algal cultures. J Microbiol Methods. (2010)
  8. ^ a b Park JY1, et al. Changes in fatty acid composition of Chlorella vulgaris by hypochlorous acid. Bioresour Technol. (2014)
  9. ^ a b Mišurcová L1, et al. Amino acid composition of algal products and its contribution to RDI. Food Chem. (2014)
  10. ^ Kittaka-Katsura H, et al. Purification and characterization of a corrinoid compound from Chlorella tablets as an algal health food. J Agric Food Chem. (2002)
  11. ^ Watanabe F, et al. Characterization and bioavailability of vitamin B12-compounds from edible algae. J Nutr Sci Vitaminol (Tokyo). (2002)
  12. ^ a b Uchikawa T, et al. Chlorella suppresses methylmercury transfer to the fetus in pregnant mice. J Toxicol Sci. (2011)
  13. ^ Tamaki H, et al. Inhibitory effects of herbal extracts on breast cancer resistance protein (BCRP) and structure-inhibitory potency relationship of isoflavonoids. Drug Metab Pharmacokinet. (2010)
  14. ^ a b Rai UN1, et al. Chromate tolerance and accumulation in Chlorella vulgaris L.: role of antioxidant enzymes and biochemical changes in detoxification of metals. Bioresour Technol. (2013)
  15. ^ Algal Biomass: An Economical Method for Removal of Chromium from Tannery Effluent.
  16. ^ Jiang Y1, et al. Effects of arsenate (AS5+) on growth and production of glutathione (GSH) and phytochelatins (PCS) in Chlorella vulgaris. Int J Phytoremediation. (2011)
  17. ^ Karadjova IB1, Slaveykova VI, Tsalev DL. The biouptake and toxicity of arsenic species on the green microalga Chlorella salina in seawater. Aquat Toxicol. (2008)
  18. ^ Wu Y1, Wang WX. Accumulation, subcellular distribution and toxicity of inorganic mercury and methylmercury in marine phytoplankton. Environ Pollut. (2011)
  19. ^ Uchikawa T, et al. Enhanced elimination of tissue methylmercury in Parachlorella beijerinckii-fed mice. J Toxicol Sci. (2011)
  20. ^ Uchikawa T, et al. The influence of Parachlorella beyerinckii CK-5 on the absorption and excretion of methylmercury (MeHg) in mice. J Toxicol Sci. (2010)
  21. ^ The Prevalence of Anemia in Women.
  22. ^ Kusumi E, et al. Prevalence of anemia among healthy women in 2 metropolitan areas of Japan. Int J Hematol. (2006)
  23. ^ Matsuura E, et al. Effect of chlorella on rats with iron deficient anemia. Kitasato Arch Exp Med. (1991)
  24. ^ a b c d e f g Nakano S, Takekoshi H, Nakano M. Chlorella pyrenoidosa supplementation reduces the risk of anemia, proteinuria and edema in pregnant women. Plant Foods Hum Nutr. (2010)
  25. ^ a b c d Shimada M, et al. Anti-hypertensive effect of gamma-aminobutyric acid (GABA)-rich Chlorella on high-normal blood pressure and borderline hypertension in placebo-controlled double blind study. Clin Exp Hypertens. (2009)
  26. ^ a b c Lee SH, et al. Six-week supplementation with Chlorella has favorable impact on antioxidant status in Korean male smokers. Nutrition. (2010)
  27. ^ a b Nakashima Y, et al. Preventive effects of Chlorella on cognitive decline in age-dependent dementia model mice. Neurosci Lett. (2009)
  28. ^ a b c Mizoguchi T, et al. Nutrigenomic studies of effects of Chlorella on subjects with high-risk factors for lifestyle-related disease. J Med Food. (2008)
  29. ^ a b Merchant RE, Carmack CA, Wise CM. Nutritional supplementation with Chlorella pyrenoidosa for patients with fibromyalgia syndrome: a pilot study. Phytother Res. (2000)
  30. ^ Merchant RE, Andre CA. A review of recent clinical trials of the nutritional supplement Chlorella pyrenoidosa in the treatment of fibromyalgia, hypertension, and ulcerative colitis. Altern Ther Health Med. (2001)
  31. ^ a b 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. Nutr J. (2011)
  32. ^ Lamm ME, et al. IgA and mucosal defense. APMIS. (1995)
  33. ^ Klentrou P, et al. Effect of moderate exercise on salivary immunoglobulin A and infection risk in humans. Eur J Appl Physiol. (2002)
  34. ^ Gleeson M, et al. Salivary IgA levels and infection risk in elite swimmers. Med Sci Sports Exerc. (1999)
  35. ^ a b Nakano S, Takekoshi H, Nakano M. Chlorella (Chlorella pyrenoidosa) supplementation decreases dioxin and increases immunoglobulin a concentrations in breast milk. J Med Food. (2007)
  36. ^ 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)
  37. ^ Lai KM, Scrimshaw MD, Lester JN. Biotransformation and bioconcentration of steroid estrogens by Chlorella vulgaris. Appl Environ Microbiol. (2002)
  38. ^ Ge L, et al. Photodegradation of 17beta-estradiol induced by Chlorella vulgaris. Ying Yong Sheng Tai Xue Bao. (2004)
  39. ^ Hirooka T, et al. Biodegradation of bisphenol A and disappearance of its estrogenic activity by the green alga Chlorella fusca var. vacuolata. Environ Toxicol Chem. (2005)