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Chlorella
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In one pass Chlorella is a single-celled green alga, dried and ground into a powder that is sold as a supplement.
Educational content, not medical advice — consult a clinician.
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Chapter 1
Chlorella is not spirulina
Chlorella is a single-celled green alga, dried and ground into a powder that is sold as a supplement. Thinking of it as a concentrated vegetable powder is roughly right. Marketing hangs three claims on it, and it cannot carry any of them. It is not a vegan B12 source you can rely on, because the label cannot tell you how much real B12 the jar in your hand contains. The claim that it clears heavy metals from your body comes from mouse experiments, with no solid human evidence. And because it grows in water, it can itself soak up heavy metals from that water, so product quality depends on the water source and on testing.
It is a eukaryotic green alga only a few micrometers across, wrapped in a cellulose cell wall that people cannot digest, so commercial products are mechanically cracked first. Do not confuse it with spirulina: spirulina is actually a cyanobacterium (once called blue-green algae).
More than half of the dry powder is protein (50–60%), and it also carries chlorophyll, carotenes, iron and B vitamins. Most of what it offers, dark leafy greens offer too, for far less money.
It is a eukaryotic green alga only a few micrometers across, wrapped in a cellulose cell wall that people cannot digest, so commercial products are mechanically cracked first. Do not confuse it with spirulina: spirulina is actually a cyanobacterium (once called blue-green algae).
More than half of the dry powder is protein (50–60%), and it also carries chlorophyll, carotenes, iron and B vitamins. Most of what it offers, dark leafy greens offer too, for far less money.
Background · Where its reputation came from
How did it pick up the reputation it carries today? In the fifties and sixties of the last century, the UN and Japan hoped it would ease a global protein shortage, because algae grown in ponds yield far more protein per area than soybeans do. But it was expensive, tasted poor, and its cell wall made it hard to digest, so it never became a staple food. It was repackaged as a superfood, and by the 2020s it had also been labeled a heavy-metal remover and a vegan B12 source.Only three statements about it hold up today:
As food: its nutrient density is decent, but for the same nutrition it costs far more than dark leafy greens such as spinach or kale, and it has no special advantageAs a supplement: most of the drug-like effects in its marketing have no (RCT) behind themAs a detox agent: that is an over-extrapolation from studies that fed mice
Chapter 2
Why it can't supply B12
Chlorella can contain real B12. The problem is how much the jar you bought contains, and the label cannot answer that.
Real B12 has a cobalt atom at its center, with a small part called DMB hanging beneath the cobalt; the two enzymes in your body that use B12 recognize it by that part. Algae and bacteria also make look-alike molecules in which that part has been swapped for something else. Together they are called pseudo-B12 (corrinoid analogues), and they are inactive in the human body.
What has been measured in chlorella tablets is mostly real B12, which puts it ahead of spirulina. But content across products runs from almost none to a great deal, a spread of several thousandfold, and some high-content products also carry inactive analogues.
So it cannot serve as a vegan's B12 plan. The reliable sources are fortified foods and B12 supplements.
Real B12 has a cobalt atom at its center, with a small part called DMB hanging beneath the cobalt; the two enzymes in your body that use B12 recognize it by that part. Algae and bacteria also make look-alike molecules in which that part has been swapped for something else. Together they are called pseudo-B12 (corrinoid analogues), and they are inactive in the human body.
What has been measured in chlorella tablets is mostly real B12, which puts it ahead of spirulina. But content across products runs from almost none to a great deal, a spread of several thousandfold, and some high-content products also carry inactive analogues.
So it cannot serve as a vegan's B12 plan. The reliable sources are fortified foods and B12 supplements.
Mechanism · What separates B12 from look-alikes
The chemical name of B12 is cobalamin. Its chemistry in brief:Real B12 comes in four common forms. Methylcobalamin and adenosylcobalamin are the two coenzyme forms that do the work in the body; cyanocobalamin is the stable form most supplements use; hydroxocobalamin is mostly used in injectable drugsShared structure: a corrin ring, a cobalt (Co) atom at its center, and 5,6-dimethylbenzimidazole (DMB) hanging below the cobaltDMB is the part that gets recognized; the line between real B12 and its analogues runs through it
In a corrinoid analogue, what hangs below the cobalt is not DMB but adenine, methyladenine or another imidazole-type group (the main pseudo-B12 in spirulina carries adenine). For the two mammalian enzymes that depend on B12, methionine synthase and methylmalonyl-CoA mutase, these molecules have no coenzyme activity; the Watanabe 2014 review classes them as biologically inactive in humans.
Whether they interfere with the absorption of real B12 in the body, or push a blood B12 reading up, has not been measured directly, so no conclusion is drawn here. Some archaea and bacteria make these DMB-free analogues, and they are often mistaken for B12.
Evidence · How much real B12 chlorella holds
Put the studies side by side:Watanabe 2002 purified the corrinoids from several edible algae. In chlorella tablets, real B12 was the main form; in spirulina tablets it was the reverse, with pseudo-B12 dominatingWatanabe 1999 purified two corrinoids from spirulina tablets: 83% was pseudo-B12 and 17% real B12The Bito 2020 review pooled measurements of chlorella products: B12 content ranged from under 0.1 µg to about 400 µg per 100 g of dry weightChlorella does not need B12 to grow; it absorbs and stores B12 from its culture environment. In open culture, Chlorella pyrenoidosa holds far more than Chlorella vulgarisSome high-B12 products also contain inactive corrinoids, such as 5-methoxybenzimidazolylcobamide and cobalt-free corrinoids; telling real from fake takes a laboratory method such as liquid chromatography–tandem mass spectrometry
Human data are scarce. In one study cited by Bito 2020, vegetarians with suspected B12 deficiency took 9 g of Chlorella pyrenoidosa a day for 60 days. Serum (MMA, a metabolite that builds up when B12 runs short) fell in 88% of them, and fell too; serum B12 only trended upward, and anemia markers such as hemoglobin did not change. It was a small study with no control group.
So the B12 in some chlorella products can likely be used by the body. But how much a given jar contains, and how much analogue is mixed in, you cannot judge from the label. B12 needs are counted in micrograms (2.4 µg a day for adults), so a small shortfall in content is a large shortfall in supply. For vegans the reliable sources are fortified foods (nutritional yeast, fortified plant milks, fortified breakfast cereals) and B12 supplements (cyanocobalamin or methylcobalamin). That is the consensus of EFSA, the German Nutrition Society (DGE) and the Academy of Nutrition and Dietetics.
Safety · What happens if you rely on it for B12
Taking chlorella is the vegan B12 source at face value does real harm here:A vegan who uses it in place of a B12 supplement can slide into deficiency without noticing. Megaloblastic anemia and irreversible nerve damage (peripheral neuropathy, subacute combined degeneration of the spinal cord) can develop, and they are easy to missSerum (MMA) and show a deficiency earlier than serum B12 alone, so test them togetherPeople who need to be especially careful:Older vegans (absorption declines with age)People who have eaten a strict vegan diet for years (liver stores run down slowly)Pregnant vegans (a mother's B12 deficiency can cause irreversible nerve damage in the baby)
A reliable vegan B12 plan, the same as in the Vitamin B12 story:
Fortified foods at least twice a day, at least 3 µg in total, orOne supplement of at least 10 µg a day (cyanocobalamin or methylcobalamin), orOne high-dose 2000 µg tablet a weekA yearly blood test for serum B12, MMA and homocysteine
Chlorella has no place in this plan: its content is unreliable, it varies from batch to batch, and it is expensive.
Evidence · How the B12 on a label is measured
How the B12 figure on a label was measured decides how far you can trust it. This is about testing the product itself, not your blood test:Microbiological assay (a Lactobacillus assay): some analogues also let the bacteria grow, so the reading runs high. When Watanabe 1999 tested spirulina tablets, the microbiological assay gave values about 6–9 times higher than the intrinsic-factor chemiluminescence assayThe intrinsic-factor chemiluminescence assay does not separate them cleanly either: in the same study, 83% of the corrinoids this method picked up were pseudo-B12Liquid chromatography–tandem mass spectrometry (LC-MS/MS) can separate real B12 from its analogues and is the most accurate method, but it is expensive and most products are not tested this way
So chlorella cannot replace a real B12 supplement. It does better than spirulina, but far worse than fortified foods plus a B12 supplement. If you eat a vegan or mostly plant-based diet, a daily B12 plan and a yearly blood test are not optional; chlorella is at most an optional extra, never a substitute.
Chapter 3
Where the detox claim came from
The claim that chlorella clears heavy metals was not made up. It has a real scientific starting point, but that starting point is in animals. There is still no evidence that it improves any kind of heavy-metal poisoning in people.
The starting point is these studies:
Uchikawa 2011: mice given methylmercury were also fed a chlorella strain (Parachlorella beijerinckii CK-5); they excreted more mercury in their feces and had less mercury in brain and bloodMorita 1999: in rats, chlorella increased the fecal excretion of dioxinsPore 1984: in a test tube, algal cells bound heavy-metal ions
The mechanistic hypothesis is that the algal cell wall and fiber hold on to methylmercury in the gut, so less of it is reabsorbed and more leaves in the feces. These are real studies, but they are a long way from a clinical recommendation to clear heavy metals from people.
The starting point is these studies:
Uchikawa 2011: mice given methylmercury were also fed a chlorella strain (Parachlorella beijerinckii CK-5); they excreted more mercury in their feces and had less mercury in brain and bloodMorita 1999: in rats, chlorella increased the fecal excretion of dioxinsPore 1984: in a test tube, algal cells bound heavy-metal ions
The mechanistic hypothesis is that the algal cell wall and fiber hold on to methylmercury in the gut, so less of it is reabsorbed and more leaves in the feces. These are real studies, but they are a long way from a clinical recommendation to clear heavy metals from people.
Evidence · The steps between mouse and human
Jumping from mouse to human means crossing four steps, and none of them has been demonstrated:Step one is dose:
In animal experiments, chlorella often makes up a large share of the feed; in the rat blood-pressure experiments in the Bito 2020 review, it made up 5%, 10% and 20% of the dietScaled to a person by body weight, that is tens to hundreds of grams of dried powder a day; people taking a supplement usually take 3–5 g a dayThe two differ by one to two orders of magnitude
Step two is how the exposure happens:
Animal models receive one large dose, force-fedPeople are exposed to small amounts over years (fish, rice, dental amalgam fillings)The kinetics inside the body are completely different
Step three is measurement:
Animal experiments can dissect the animal and measure mercury in the brain and liver directlyIn people only blood, urine or hair can be measured, and these do not reflect how much sits in the tissuesA rise in urinary mercury is not detox; the mercury may simply have moved somewhere else in the body
Step four is clinical meaning:
Animal and test-tube work only shows that it can bind mercuryNo human (RCT) shows that chlorella improves the symptoms or outcome of mercury poisoning
Where the human research stands:
An open-label trial cited in the Bito 2020 review: healthy volunteers took 9 g of Parachlorella a day for 3 months, and mercury in their hair and blood fell. It had no control group and measured no health outcomeNo large, independent RCT has repeated itNo RCT has tested whether it improves the outcome in adults who already have symptoms of mercury poisoning
Clinical · Who to see for real poisoning
Here is how real heavy-metal detox works in clinical practice:Actual heavy-metal poisoning (mercury, lead, arsenic, cadmium):Urgent medical evaluationChelation therapy: DMSA (succimer) or DMPS, and EDTA for severe lead poisoning, all under the guidance of a toxicologistNot chlorellaPreventive detox:Healthy people do not need chlorella to detoxReal prevention means cutting exposure: eat fewer large fish that are high in mercury, avoid lead-containing cosmetics, keep household dust down, and talk with your dentist about filling materialsWorried about amalgam fillings:Most dental and regulatory bodies consider the exposure from amalgam low for the general populationIf you are truly worried, discuss switching to resin with your dentistThe claim that taking chlorella around removal protects you has no evidence either
The biggest irony:
Chlorella grows in water and soaks up heavy metals from it; in test-tube work, that very ability is what lets it bind heavy-metal ionsSo whether a product is clean depends entirely on the culture water and on testingBe clear about where algal toxins come from: Heussner 2012 tested 13 algae supplements sold in Germany and found microcystins only in products containing Aphanizomenon flos-aquaeTaking something that may itself carry mercury in order to get rid of mercury could leave you taking in more
What to look for in a product:
Grown in controlled water (for example reverse-osmosis or distilled water), with GMP certificationPublishes third-party heavy-metal test resultsAvoid products from open ponds of unknown origin, and brands that will not publish their test results
If you really have heavy-metal poisoning, see a toxicologist and use DMSA, DMPS or EDTA, not chlorella. Healthy people who cut their exposure and eat a varied diet do not need to detox. Influencers and naturopathic practitioners who recommend it for detox are running far ahead of the evidence.
Chapter 4
What chlorella may actually help
Take away the detox and B12 claims, and what is left for chlorella is small samples and weak signals.
Immunity is the most credible of these. In a randomized double-blind trial (Kwak 2012), healthy adults took 5 g a day for 8 weeks; the activity of natural killer cells in their blood (the team that clears out abnormal cells) rose, and several immune signaling molecules rose too. One hypothesis is that β-glucans and other polysaccharides on the algal wall are recognized by the dectin-1 receptor on immune cells, nudging innate immunity up one notch; that step has not been measured directly in people.
Blood lipids and blood pressure: a cited in the Bito 2020 review pooled 19 and found improvements in total cholesterol, , blood pressure and fasting glucose, but not in or . The changes were small.
Notice that what moved was numbers on a lab report, not how you feel. More active natural killer cells do not mean fewer colds; the studies never measured that outcome.
Immunity is the most credible of these. In a randomized double-blind trial (Kwak 2012), healthy adults took 5 g a day for 8 weeks; the activity of natural killer cells in their blood (the team that clears out abnormal cells) rose, and several immune signaling molecules rose too. One hypothesis is that β-glucans and other polysaccharides on the algal wall are recognized by the dectin-1 receptor on immune cells, nudging innate immunity up one notch; that step has not been measured directly in people.
Blood lipids and blood pressure: a cited in the Bito 2020 review pooled 19 and found improvements in total cholesterol, , blood pressure and fasting glucose, but not in or . The changes were small.
Notice that what moved was numbers on a lab report, not how you feel. More active natural killer cells do not mean fewer colds; the studies never measured that outcome.
Evidence · The immune and blood-lipid trials
Certainty of evidence: low (a few small randomized trials pointing roughly the same way, but with small samples and mostly lab markers as outcomes).1. Immune modulation and natural killer cells (NK cells):
Kwak 2012 (Nutrition Journal), randomized, double-blind and placebo-controlled, N=51 healthy adults: 5 g of chlorella a day for 8 weeksNK-cell activity rose; interferon-γ and interleukin-1β, two early inflammatory signals, rose as well, while interleukin-12 only showed a trend upward that did not reach statistical significanceThese are all blood markers; the trial did not count infections
2. Blood lipids:
Ryu 2014 and other small trials (adults with mildly high cholesterol, 5 g of chlorella for 4 weeks) reported falls in and total cholesterolBut in the cited in the Bito 2020 review (19 , 797 people), total cholesterol and improved while triglycerides and did notThe signal is weak and cannot replace lifestyle change or drugs
ryu-2014-chlorella-lipids
Evidence · Blood pressure, pregnancy, exercise
3. Blood pressure (very weak evidence):In two small human trials described in the Bito 2020 review, blood pressure barely changed (one of them in 24 people with mild to moderate hypertension, over 2 months)The pooling 19 trials found some fall in systolic and diastolic pressure, far smaller than what exercise or a DASH diet achieves
4. Nutrition in pregnancy (Japanese data):
Nakano 2010, 70 pregnant women in Japan; the chlorella group took 6 g a day until deliveryFewer women were anemic in the second and third trimesters, and proteinuria and edema were less common in the third trimesterThe authors attribute this to the folate, B12 and iron in the alga; that has not been shown directlyNote: the Japanese diet is unusual (a lot of fish), so the result may not carry over to other diets
5. Exercise performance (extremely weak):
A few small studies looked at aerobic performance and antioxidant markersThe signal is faint and no larger than the effect of eating dark leafy greens
Directions where the evidence is very low or absent:
Weight loss: body mass index () did not improve in the meta-analysisCancer: only test-tube studies, no clinical dataPreventing or treating COVID: no (RCT)Diabetes: fasting glucose improved slightly in the meta-analysis, but no trial has looked at diabetes outcomes themselves
nakano-2010-chlorella-pregnancy
In practice · Against greens and other powders
Where it makes the most sense:If you want a concentrated green vegetable: one scoop of the powder covers part of the nutrition of a small serving of dark leafy greensConvenience: on business trips, while traveling, or in a dorm without a kitchen, the powder is easier to carry than vegetablesPrice: for the same nutrition, it costs far more than spinach
Side by side with other green supplements:
| Chlorella | Spirulina | Matcha | Barley grass powder | |
|---|---|---|---|---|
| Protein | 50–60% (Bito 2020) | Also over half | Lower | Lowest |
| Chlorophyll | High | Medium | Medium | Medium |
| Real B12 | In some products | Almost none | None | None |
| Human trials | A few small RCTs | A few small RCTs | Very few | Very few |
| Price per gram of protein | High | High | Very high | Medium |
in the table means randomized controlled trial.
Against simply eating vegetables:
100 g of raw spinach:2.9 g of protein (the USDA food-composition value; the same weight of chlorella holds 50–60 g, per Bito 2020)Chlorophyll at a lower concentration than chlorellaA whole food structure: fiber, polyphenols and many nutrientsNo corrinoid analoguesLittle heavy metalFar cheaperConclusion: if you can eat vegetables, eat vegetables; on days when you truly cannot, chlorella can fill part of the gap
Safety · Who should ask a doctor first
What it actually is:Not a superfood: nobody can say what makes it superNot a reliable vegan B12 source: its content cannot be pinned downNot a heavy-metal detoxifier: there are only animal dataA fairly nutrient-dense green vegetable powder, worth considering when eating vegetables is inconvenientA supplement with weak immune and blood-lipid signals, whose effect falls short of eating more dark vegetables, exercising and sleeping enough combined
Safety and drug interactions:
Fairly high in vitamin K: if you take warfarin, use it with caution and discuss it with your doctor firstFairly high in iodine (depending on the source): use with caution if you have hyperthyroidismGut discomfort: a lot of fiber plus the cell wall cause bloating or diarrhea in some peopleAllergy: rare, but reported (to the algal protein)People on immunosuppressants: it stimulates the immune system and could in theory work against the drug, so use cautionPregnancy: the Japanese pregnancy study was small and the safety data are incomplete, so discuss it with your doctor first
Chapter 5
Should I take it?
Whether to take it depends on what you want it to replace.
The jobs it cannot do happen to be the ones marketing shouts about loudest: clearing heavy metals (healthy people do not need it, and real exposure calls for a doctor), serving as a vegan's B12 source (its content cannot be pinned down, so it cannot be relied on), and working as an all-purpose pill against cancer, inflammation, weight gain and aging (none of these has a proper behind it).
There is only one job it can cover for a while: a stretch when you truly cannot get leafy greens, such as business travel, dorm life, or overtime with no time to cook. Then a scoop of algal powder that makes up part of the nutrition of leafy greens is a case of the worst option still beats nothing, not a stand-in for vegetables.
Two groups should not decide on their own: people who are pregnant or breastfeeding, and people taking warfarin or other anticoagulants, immunosuppressants, or drugs for an overactive thyroid. The vitamin K, iodine and immune-stimulating parts of the powder can interfere, so in these cases please talk with your doctor first.
The jobs it cannot do happen to be the ones marketing shouts about loudest: clearing heavy metals (healthy people do not need it, and real exposure calls for a doctor), serving as a vegan's B12 source (its content cannot be pinned down, so it cannot be relied on), and working as an all-purpose pill against cancer, inflammation, weight gain and aging (none of these has a proper behind it).
There is only one job it can cover for a while: a stretch when you truly cannot get leafy greens, such as business travel, dorm life, or overtime with no time to cook. Then a scoop of algal powder that makes up part of the nutrition of leafy greens is a case of the worst option still beats nothing, not a stand-in for vegetables.
Two groups should not decide on their own: people who are pregnant or breastfeeding, and people taking warfarin or other anticoagulants, immunosuppressants, or drugs for an overactive thyroid. The vitamin K, iodine and immune-stimulating parts of the powder can interfere, so in these cases please talk with your doctor first.
In practice · Three narrow cases worth considering
A few narrow cases worth considering:1. Convenience: a life where you cannot get leafy greens every day
Business travel, student life, overtime with no time to cook1–3 g of chlorella covers part of the nutrition of leafy greensDo not use it to replace vegetables; it is a the worst option still beats nothing choice2. A blood test shows a mild shortfall and your diet is monotonous
For example low iron, some B vitamins or β-caroteneCorrect the deficiency itself on your doctor's plan; the powder can only be one part of a varied diet, not a substitute3. You want to try it for immune support (frequent mild colds)
The basis is the signal from the Kwak 2012 trial: 5 g a day for 8 weeks, which measured blood markers, not the number of coldsPair it with enough sleep, exercise and adequate vitamin D
In practice · Six cases where it is not worth it
Cases where it is not worth it or not recommended:1. Heavy-metal detox
Healthy people do not need itFor real heavy-metal exposure, see a doctor, not chlorella2. A vegan B12 source
Its content cannot be pinned down, and some products also carry inactive analoguesUse a cyanocobalamin or methylcobalamin supplement, plus a yearly blood test3. An all-purpose pill against cancer, inflammation, aging or weight gain
No (RCT) dataThe gap between expectation and reality is huge4. Pregnancy and breastfeeding (not by default)
The Japanese pregnancy study was small and the safety data are incompleteAccumulated heavy metals are a risk to the fetusDiscuss it with your obstetrician5. Taking warfarin, a direct oral anticoagulant (), immunosuppressants or drugs for an overactive thyroid
Its vitamin K, its iodine and its immune stimulation can all clash with these drugsDiscuss it with your doctor first6. Healthy people taking a daily green powder
Just eat vegetables: far cheaper, a whole food structure, and no problem with absorbed heavy metals
In practice · How to choose if you buy it
If you do use it, choose like this:A clear country of origin and manufacturer (GMP-certified beats unknown)A stated cell-wall cracking process, which improves digestibilityPublished third-party test results for heavy metals (lead, arsenic, mercury, cadmium)An algal-toxin test result that reads not detectedSpecies:Chlorella vulgaris: the most commonChlorella pyrenoidosa: in open culture, far higher in B12 than Chlorella vulgaris (Bito 2020)Parachlorella beijerinckii: used by some Japanese brandsAvoid: unknown origin, a label that says organic but has no heavy-metal testing, a heavy-metal detox pitch (itself a marketing red flag), and suspiciously cheap products
Dose guide:
As a food supplement: 3–5 g a dayDoses used in trials (immunity, lipids, pregnancy, B12): 5–10 g a dayDo not go above 10 g a day: more brings no extra benefit, and gut discomfort and your vitamin K and iodine intake rise with itTaking it with meals is fine
In practice · How to tell if it works for you
To find out whether it actually does anything for you, test it like this:Watch objective markers: blood lipids, iron, B12, , and the number of colds you logMeasure a baseline before you start, then retest after 8–12 weeksIf the objective markers have not improved, stopI feel more energetic may come from the placebo effect, from expectation, or from other changes made in the same period
In the end, chlorella is a fairly nutrient-dense green vegetable powder. It is not a drug, not a detoxifier, and not a vegan's B12 savior.
If you have a real nutritional deficiency: eat a varied diet and, when needed, take the specific nutrient (B12, vitamin D, iron). If you are worried about heavy metals: cut your exposure and get a medical evaluation. If you have a real immune problem: sleep enough, exercise, keep vitamin D and zinc adequate, and get a medical evaluation when needed.
In each of these cases chlorella is far from the best choice. It can be a convenience aid, not the main road. Marketing uses natural, concentrated, complete nutrition to make it look like a shortcut; in reality it is a much more expensive detour.
References · 7
- Bito, T., Okumura, E., Fujishima, M., & Watanabe, F. (2020). Potential of Chlorella as a dietary supplement to promote human health. Nutrients, 12(9), 2524. Reviews cardiometabolic and immune RCTs — small N, heterogeneous extracts, modest signals; also discusses B12 corrinoid composition. Full text: a meta-analysis of 19 randomized controlled trials (797 subjects) found chlorella improved total cholesterol, LDL-C, systolic and diastolic blood pressure and fasting glucose but not triglycerides, HDL-C or BMI. Reported B12 content of chlorella products ranges from < 0.1 to 400 µg per 100 g dry weight. Vegans with elevated serum methylmalonic acid who took 9 g C. pyrenoidosa daily for 60 days: MMA fell in 88%, homocysteine fell, serum B12 tended to rise, MCV, hemoglobin and hematocrit unchanged (the primary paper, Merchant 2015, PMID 26485478, is an exploratory open-label study of 17 adults: MMA fell about 34% on average and 15 of 17 had at least a 10% drop). Blood pressure: a pilot in 24 people with mild to moderate hypertension given 10 g tablets plus 100 mL extract for 2 months saw heart rate and sitting blood pressure change only slightly. Pregnancy: 32 women given 6 g/day for 12-18 weeks had fewer anemia markers than controls. The authors declare no conflict of interest (full text, PMC7551956; abstract, PMID 32825362). 10.3390/nu12092524
- Watanabe, F., Takenaka, S., Kittaka-Katsura, H., Ebara, S., & Miyamoto, E. (2002). Characterization and bioavailability of vitamin B12-compounds from edible algae. Journal of Nutritional Science and Vitaminology, 48(5), 325-331. Chlorella pyrenoidosa contains a mix of true cobalamin and inactive corrinoid analogues; bioavailability in B12-deficient humans not demonstrated. Abstract: B12 measured by microbiological assay, then the corrinoids purified. True vitamin B12 is the predominant cobamide in green and purple laver and in chlorella tablets; feeding purple laver to B12-deficient RATS significantly improved their B12 status; pseudovitamin B12, an inactive corrinoid, predominated in spirulina tablets, which the authors call unsuitable as a B12 source, especially for vegetarians (abstract, PMID 12656203). 10.3177/jnsv.48.325
- Watanabe, F., Katsura, H., Takenaka, S., et al. (1999). Pseudovitamin B(12) is the predominant cobamide of an algal health food, spirulina tablets. Journal of Agricultural and Food Chemistry, 47(11), 4736-4741. Spirulina tablets: the Lactobacillus leichmannii microbiological assay gave values about 6-9-fold greater than the intrinsic-factor chemiluminescence assay, because most of the microbiologically measured 'B12' was substitutive compounds or inactive analogues. Of the two intrinsic-factor-active analogues purified, the major one (83%) was pseudovitamin B12 and the minor one (17%) vitamin B12 (abstract, PMID 10552882). 10.1021/jf990541b
- Watanabe, F., Yabuta, Y., Bito, T., & Teng, F. (2014). Vitamin B12-containing plant food sources for vegetarians. Nutrients, 6(5), 1861-1873. B12 is synthesized only by bacteria and archaea, not by plants or fungi, and most plant foods are unreliable sources that may carry inactive corrinoid analogs. ⚠️ The review's own conclusion, however, is that dried purple laver (nori) is the MOST SUITABLE naturally occurring vitamin B12 source presently available for vegetarians, and that it additionally supplies iron and n-3 fatty acids that vegetarian diets tend to lack. Do not cite this paper for the claim that nori B12 is inactive. Full text: supplements made from edible cyanobacteria (Spirulina, Aphanizomenon, Nostoc) often contain large amounts of pseudovitamin B12, which is biologically inactive in humans; chlorella tablets contain biologically active vitamin B12, but the authors' unpublished data show contents from zero to several hundred µg per 100 g dry weight, so users should check the label (full text, PMC4042564; abstract, PMID 24803097). 10.3390/nu6051861
- Uchikawa, T., Kumamoto, Y., Maruyama, I., Kumamoto, S., Ando, Y., & Yasutake, A. (2011). Enhanced elimination of tissue methylmercury in Parachlorella beijerinckii-fed mice. Journal of Toxicological Sciences, 36(1), 121-126. Mouse data — supports the 'binds methylmercury' marketing claim mechanistically only; no human chelation RCT. Female C57BL/6N mice given one oral dose of methylmercury chloride (5 mg/kg) were fed 0%, 5% or 10% Parachlorella powder for 3 weeks: blood mercury fell significantly from day 7, cumulative urinary (5%) and fecal (5% and 10%) mercury excretion rose, and at day 21 kidney and brain mercury were significantly lower (liver not); glutathione did not change. Title and author order corrected on 2026-09-24 to match the DOI; the title previously given belongs to the same group's 2010 paper, J Toxicol Sci 35(1), 101-105 (abstract, PMID 21297350). 10.2131/jts.36.121
- Heussner, A. H., Mazija, L., Fastner, J., & Dietrich, D. R. (2012). Toxin content and cytotoxicity of algal dietary supplements. Toxicology and Applied Pharmacology, 265(2), 263-271. A laboratory analysis of products, not a cohort: 13 algae supplements sold in Germany (Aphanizomenon flos-aquae, spirulina, chlorella or mixtures) plus 5 re-analysed from an earlier market study. Microcystins were found only in products containing A. flos-aquae (<= 1 µg MC-LR equivalents per g dry weight); no other toxins were found in any product, so none in pure spirulina; extracts of all products were cytotoxic to A549 cells. Despite the id, the abstract reports no heavy metals (abstract, PMID 23064102). 10.1016/j.taap.2012.10.005
- Kwak, J. H., Baek, S. H., Woo, Y., Han, J. K., Kim, B. G., Kim, O. Y., & Lee, J. H. (2012). Beneficial immunostimulatory effect of short-term Chlorella supplementation: enhancement of natural killer cell activity and early inflammatory response (randomized, double-blinded, placebo-controlled trial). Nutrition Journal, 11, 53. 8-week randomized, double-blind, placebo-controlled trial in healthy adults: 5 g/day chlorella tablets (n = 23) vs placebo (n = 28). Serum interferon-gamma (p < 0.05) and interleukin-1beta (p < 0.001) rose significantly and interleukin-12 only tended to rise (p < 0.1) in the chlorella group, with larger increments than placebo; NK-cell activity rose on chlorella but not placebo. Outcomes were NK activity and serum cytokines only (abstract, PMID 22849818). 10.1186/1475-2891-11-53