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Spirulina
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In one pass Spirulina is not, strictly speaking, an alga. Not this — Spirulina = vegan B12 source — It contains pseudo-B12, a look-alike that cannot activate the human enzymes that depend on B12 — and it may even crowd real B12 off its receptors.
Educational content, not medical advice — consult a clinician.
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Chapter 1
It's a bacterium, not an alga
Spirulina is not, strictly speaking, an alga. It is a cyanobacterium — the kind of microbe that rises as a film on the surface of a pond — and it belongs to a completely different family from kelp or nori.
Its nutrition is genuinely decent: the dry powder is 60–70% protein, with iron, β-carotene and a fatty acid that is rare in food. But the real question was never whether it has nutrients. It is how much it adds to what you already eat. The nutrition table in the ads is calculated per 100 g of dry powder, while a daily serving is a few grams. Scaled back to that, one egg, one serving of red meat or half a carrot matches or beats it.
The two things that deserve real caution are different. Most of the B12 on the label is pseudo-B12, a look-alike the human body cannot use, so a strict vegan who relies on it for B12 is left short. And powder grown in open ponds can also carry heavy metals and algal toxins from the water.
Its nutrition is genuinely decent: the dry powder is 60–70% protein, with iron, β-carotene and a fatty acid that is rare in food. But the real question was never whether it has nutrients. It is how much it adds to what you already eat. The nutrition table in the ads is calculated per 100 g of dry powder, while a daily serving is a few grams. Scaled back to that, one egg, one serving of red meat or half a carrot matches or beats it.
The two things that deserve real caution are different. Most of the B12 on the label is pseudo-B12, a look-alike the human body cannot use, so a strict vegan who relies on it for B12 is left short. And powder grown in open ponds can also carry heavy metals and algal toxins from the water.
Numbers · The label table, scaled to a daily dose
The nutrition table that gets quoted everywhere only means something once you convert it to the amount you actually swallow in a day.First, what it is. Spirulina, strictly speaking, is not an alga but a cyanobacterium; commercial product comes mainly from two species, *Arthrospira platensis* and *Arthrospira maxima*. They belong to the oldest photosynthetic life on Earth, and close relatives already appear in 3.5-billion-year-old fossils.
The nutrition table (per 100 g of dry powder):
Protein, 60-70%: its loudest selling point — higher than soy (40%) and meat (20-30%), with all 9 essential amino acids.Iron, about 30-50 mg: this is the non-heme iron found in plant foods, which is generally absorbed less well than the heme iron in red meat.β-carotene, 100-150 mg: an order of magnitude above carrots.Phospholipids and γ-linolenic acid (GLA): GLA is uncommon in food.Phycocyanin, 14-20%: the pigment-protein that turns it blue, its one chemically unique selling point, covered in the chapter The blue pigment has small effects.Vitamin B12, 3-25 µg/100 g: this is the figure given by labels and by the commonly used assay, and most of it is not B12 the body can use — covered in the chapter Why it can't supply B12.
⚠️ But the table is calculated per hundred grams of dry powder, and nobody eats a hundred grams a day. Convert it to a typical serving and the picture changes at once:
At 3-10 g of spirulina a day (a typical serving), you get only 2-7 g of protein; one egg covers 1-2 times that.Iron: the iron absorbed from one serving of red meat exceeds what 5-10 g of spirulina provides.β-carotene: half a carrot beats 5 g of spirulina.GLA: evening primrose oil and blackcurrant seed oil are cheaper sources.
So it is a nutritious bacterial powder. But measured by what it actually adds to your day and what it costs, it is one of the most overhyped superfoods on the supplement shelf.
Background · What the word superfood is doing
Superfood is a marketing word, not a nutrition-science term, and it is not a regulatory definition used by the US FDA, the EU's EFSA or the WHO. On the shelf it does a few jobs:It lets you skip the comparison: the word "super" stops people from asking "super compared with what, against which baseline?"It props up a premium quickly: gram for gram, spirulina powder costs far more than soy powder, and the "superfood" label makes that premium feel reasonable.It builds a scarcity story: copy about "ancient volcanic lakes" or "sacred seawater" makes a bacterium farmed industrially around the world sound mysterious.
The real supply chain:
Most commercial spirulina is grown in large ponds in countries such as China, India and Mexico.A few premium brands come from places such as Hawaii and Chenghai Lake in Yunnan, but most products on the shelf come from industrial ponds.The price difference lies mostly not in "nutrition" but in contamination control and brand story.
None of this denies that spirulina is nutrient-dense. What does not hold up is the "super, magical, cure-all" story. Its real difference from simply eating vegetables, eggs, meat and fish is far smaller than the difference in price.
If you already eat a varied whole-food diet, spirulina is one of the worst-value nutritional supplements there is. The exceptions are a few very specific, constrained situations: emergency food aid, polar expeditions, or severe loss of appetite where nutrients need to be concentrated.
Chapter 2
Why it can't supply B12
"Spirulina is a natural B12 source for vegetarians" — this is the most dangerous claim in spirulina marketing.
Much of the B12 on the label is an artifact of how it is counted. The commonly used microbiological assay counts a whole family of B12 look-alike molecules; a Japanese analysis of the same batch of spirulina tablets found the microbiological reading was 6-9 times the reading from the intrinsic-factor method, which uses the very protein the human gut absorbs B12 with. Even of the part intrinsic factor did recognize, 83% was pseudo-B12: it differs from true B12 by one small part hanging underneath, and the two enzymes in the body that actually put B12 to work cannot use it.
So a strict vegan who relies on spirulina for B12 is effectively taking none. A review of plant-based B12 sources put it plainly: edible cyanobacteria are not suitable as a B12 source for vegetarians. To cover B12, use fortified foods (fortified nutritional yeast, fortified plant milk) or a B12 supplement. One more point: whether you have enough for your body's needs shows up in two other lab tests, and a normal serum B12 alone does not tell the whole story.
Much of the B12 on the label is an artifact of how it is counted. The commonly used microbiological assay counts a whole family of B12 look-alike molecules; a Japanese analysis of the same batch of spirulina tablets found the microbiological reading was 6-9 times the reading from the intrinsic-factor method, which uses the very protein the human gut absorbs B12 with. Even of the part intrinsic factor did recognize, 83% was pseudo-B12: it differs from true B12 by one small part hanging underneath, and the two enzymes in the body that actually put B12 to work cannot use it.
So a strict vegan who relies on spirulina for B12 is effectively taking none. A review of plant-based B12 sources put it plainly: edible cyanobacteria are not suitable as a B12 source for vegetarians. To cover B12, use fortified foods (fortified nutritional yeast, fortified plant milk) or a B12 supplement. One more point: whether you have enough for your body's needs shows up in two other lab tests, and a normal serum B12 alone does not tell the whole story.
Mechanism · The one part that separates real B12
Lab reports, papers and supplement labels use a handful of names; here they are in one place.Where the chemistry differs
True B12 (cobalamin) and pseudo-B12 both have a large ring (the corrin ring) holding a cobalt atom at its center, with one ligand above and one below.In true B12 the lower ligand is 5,6-dimethylbenzimidazole (DMB); in pseudo-B12 it is adenine. The whole molecule differs by that one part.
How much of spirulina's B12 is real (Watanabe 1999, a Japanese team's analysis of commercial spirulina tablets):
The figure usually seen on labels is 3-25 µg of B12 per 100 g of dry powder, calculated with the microbiological assay.For the same batch of tablets, the microbiological reading was 6-9 times the reading from the intrinsic-factor chemiluminescence method; most of the excess was B12 substitutes and inactive analogs.The researchers then purified the fraction that binds intrinsic factor: 83% was pseudo-B12 and only 17% was true B12.
What it means inside the body
1. The absorption step: the body has three proteins that recognize B12 — intrinsic factor (IF), secreted in the stomach and responsible for absorption; transcobalamin (TCII), which carries B12 from the blood into cells; and haptocorrin (formerly called R-binder), which takes up almost any analog. Intrinsic factor is the pickiest of the three. In the analysis above, pseudo-B12 could bind intrinsic factor; whether, once in the gut, it occupies the absorption route and crowds out true B12 has not been measured directly in people.
2. The working step: the two enzymes that use B12 are methionine synthase (MTR, which turns back into methionine) and methylmalonyl-CoA mutase (MUT, which handles breakdown products of some fatty acids and amino acids). They need true B12; the Watanabe 2014 review states plainly that pseudo-B12 is biologically inactive in humans.
3. The traces left behind: when B12 falls short for the body's needs, two lab values rise first — (MMA, which piles up when MUT stalls) and homocysteine (Hcy, which piles up when MTR stalls). Routine checkups usually do not measure either.
4. Clinical consequences: megaloblastic anemia, nerve damage and depression; early symptoms are atypical, and it can take months to years before anyone notices.
So the B12 number on the label, the serum B12 reading, and whether your body actually has enough B12 to use are three different things.
Clinical · Is a normal serum B12 enough?
The defense heard most often in vegan communities is: "My friend takes spirulina and their B12 test came back normal."To read that sentence, you need to know what serum B12 measures. It measures the total amount of B12 in the blood, not whether the part your body can use is enough. In theory, analogs from food could also push the reading up if they got into the blood; this has not been measured directly in people who take spirulina. The more practical point is that serum B12, on its own, was never able to say whether B12 is sufficient for the body's needs.
Whether it is sufficient shows up in two downstream markers:
(MMA): when MUT stalls, MMA in the blood rises. It is a relatively sensitive and relatively specific marker of functional B12 deficiency. (Hcy): it rises when MTR stalls, but low folate, low vitamin B6 and reduced kidney function also raise it, so it is less specific.
The usual workup: when B12 deficiency is suspected, serum B12, MMA and Hcy are read together. A serum B12 that looks normal alongside a raised MMA suggests a functional shortfall, and the cause is worth tracking down with a doctor.
In practice: if you or someone close to you is vegan or a long-term vegetarian, do not rely on spirulina for B12. The reliable sources are a B12 supplement (cyanocobalamin or methylcobalamin) or fortified foods — for example, one 2000 µg tablet once a week, or fortified nutritional yeast and fortified plant milk every day; for the full plan and doses (see Vitamin B12). If you eat a strict vegan diet and develop numb hands or feet or an unsteady walk, see a doctor and ask for B12 and MMA tests.
This point matters more than any other claim in spirulina marketing because B12 deficiency in vegans damages nerves, and the longer it goes on, the more likely the nerve damage is not to recover fully.
Chapter 3
Metal and toxin contamination
Spirulina is grown in open or semi-open ponds, and it is a very good absorber in its own right: a large surface area, lots of protein and polysaccharide, so whatever is in the water collects on it. How much lead, mercury, arsenic and cadmium ends up in the powder therefore depends on the water source and the processing, and only batch-by-batch testing can tell you.
The other risk is microcystins: a related cyanobacterium that makes these toxins can get into the ponds. They are potent liver toxins, and microcystin-LR is classified by the International Agency for Research on Cancer (IARC) as Group 2B, possibly carcinogenic — a grade of how certain the evidence is, not of how big the risk is. A German test of 13 commercial algal supplements found microcystins only in products containing another cyanobacterium (AFA); pure spirulina had none. But extracts of every product were toxic to cells in the lab. In the United States, dietary supplements are not required to be tested batch by batch for any of this.
Pregnant women, breastfeeding women and children are advised not to take spirulina: a developing body is more sensitive to this kind of contamination, and safety data in these groups are scarce.
The other risk is microcystins: a related cyanobacterium that makes these toxins can get into the ponds. They are potent liver toxins, and microcystin-LR is classified by the International Agency for Research on Cancer (IARC) as Group 2B, possibly carcinogenic — a grade of how certain the evidence is, not of how big the risk is. A German test of 13 commercial algal supplements found microcystins only in products containing another cyanobacterium (AFA); pure spirulina had none. But extracts of every product were toxic to cells in the lab. In the United States, dietary supplements are not required to be tested batch by batch for any of this.
Pregnant women, breastfeeding women and children are advised not to take spirulina: a developing body is more sensitive to this kind of contamination, and safety data in these groups are scarce.
Safety · Where contamination comes from, how to choose
1. Heavy metals (lead, mercury, arsenic, cadmium)Spirulina has a large surface area and plenty of protein, polysaccharide and polyphenol, which makes it a very good heavy-metal absorber — people have even used it for environmental cleanup.So when the culture water carries a background of heavy metals, those metals are concentrated into the dry powder.There is no general figure for how many times they are concentrated: it depends on the water and the processing, and you have to look at batch-by-batch test reports. The German study below did not measure metals.
2. Microcystins
This is the more serious item. Commercial spirulina ponds can be contaminated by Microcystis, another cyanobacterium, which produces microcystins — liver toxins.Microcystin-LR is a potent liver toxin, and IARC lists it as Group 2B, meaning possibly carcinogenic, with limited certainty in the evidence.Heussner 2012 (13 algal supplements on the German market): microcystins were found only in products containing AFA (*Aphanizomenon flos-aquae*), at no more than 1 µg per gram of dry weight (expressed as microcystin-LR); pure spirulina and chlorella had none, and none of the other cyanotoxins tested turned up. But extracts of every product were toxic to cells in the lab.What long-term, low-dose intake does comes mainly from animal experiments; human data are limited.
3. BMAA (β-methylamino-L-alanine)
An amino acid made by cyanobacteria that is not built into proteins; it is suspected of a link with the amyotrophic lateral sclerosis–parkinsonism complex of Guam (lytico-bodig).Whether spirulina contains meaningful amounts is still disputed: some studies detect it and others do not.
4. How it is regulated
US FDA: spirulina is regulated as a dietary supplement, with no requirement for batch testing of heavy metals or toxins; nobody usually looks unless a problem surfaces.European Union: food-grade standards are relatively strict, but enforcement varies by country.Third-party certification: products certified by bodies such as NSF or USP have heavy-metal limits, but only a minority of brands choose to get certified.
How to choose:
If you still want to take it, choose a product that publishes batch-by-batch heavy-metal and microcystin results, or that carries third-party certification. Words like "natural", "organic" or "premium origin" with no test report behind them tell you nothing.
Myth · Is chlorella the better swap?
Chlorella is often marketed alongside spirulina as "the twin algae", but the chemistry and the risks of the two differ (see Chlorella).What they share:
Both are single-celled photosynthetic organisms: chlorella is a true alga (a green alga), while spirulina is a bacterium (a cyanobacterium).Both are high in protein (chlorella about 50-60%).Both are rich in chlorophyll, chlorella far more so (1-2%).Both ride the "superfood" marketing story.
Key differences:
1. B12: chlorella is also sold as a B12 source. Unlike spirulina, the Watanabe 2014 review reports that commercial chlorella tablets contain biologically active B12; but the same review also reports that the amount varies enormously between products, from almost none to a great deal. So it is still not a stable, reliable B12 source, and vegans should still use a supplement.
2. Cell wall: chlorella has a tough cellulose cell wall, which is why "broken-cell-wall chlorella" is a selling point; but the processing varies widely.
3. Heavy-metal sorption: chlorella is just as strong an absorber, with the same contamination problem.
4. Microcystins: chlorella does not make these toxins itself, so its risk is theoretically lower than spirulina's, though ponds can cross-contaminate.
Conclusion: chlorella is neither an "upgrade" of spirulina nor a "substitute" for it. In both, the marketing runs ahead of the evidence.
If what you want is the green-microalgae bundle of chlorophyll, protein and β-carotene, a serving of dark leafy greens (spinach, gai lan, kale) supplies the same group of nutrients: no heavy-metal concentration, no pseudo-B12, far cheaper, and fiber for your gut bacteria as a bonus. What you most likely need is not algae powder but more vegetables.
Chapter 4
The blue pigment has small effects
The one ingredient in spirulina that is chemically distinctive and has actually been studied in people is phycocyanin, the pigment that turns it blue; it makes up 14-20% of the dry weight.
In cell and animal experiments, its antioxidant and anti-inflammatory effects are quite consistent. In people there are only a few small trials, which saw modest improvements in measures such as allergic-rhinitis symptoms and blood lipids; the samples are small, the trials are short, and no large trial has shown a benefit on hard outcomes such as heart attack or death. The mechanism is real and there is a human signal, but both are small.
So ask the question the other way round: is that signal worth the heavy-metal, microcystin and pseudo-B12 risks, plus a sizable bill every month? A serving of blueberries, a serving of broccoli and a cup of green tea supply polyphenols, carotenoids, vitamin C and fiber without any of those risks, and for far less money.
In cell and animal experiments, its antioxidant and anti-inflammatory effects are quite consistent. In people there are only a few small trials, which saw modest improvements in measures such as allergic-rhinitis symptoms and blood lipids; the samples are small, the trials are short, and no large trial has shown a benefit on hard outcomes such as heart attack or death. The mechanism is real and there is a human signal, but both are small.
So ask the question the other way round: is that signal worth the heavy-metal, microcystin and pseudo-B12 risks, plus a sizable bill every month? A serving of blueberries, a serving of broccoli and a cup of green tea supply polyphenols, carotenoids, vitamin C and fiber without any of those risks, and for far less money.
Evidence · What phycocyanin has been tested for
Chemistry:Phycocyanin is made of two protein subunits, α and β, with a covalently attached pigment group called phycocyanobilin (PCB).PCB is an open-chain tetrapyrrole and a chemical relative of bilirubin, which is why it can likewise scavenge free radicals.Food-grade phycocyanin (sold in grades such as E18) is used in European and American candies and drinks as a natural blue coloring; it is a real food-industry product.
Clinical evidence:
Mechanism: quite consistent in cell and animal models — it reduces reactive oxygen species (, highly reactive oxygen-containing molecules that damage cell components), inhibits two enzymes that make inflammatory mediators (COX-2 and iNOS), and turns down the master inflammation switch .Human trials (the reviews by Karkos 2011 and Ku 2013): small-to-moderate signals for a few uses, all from small randomized trials.Allergic rhinitis: 1-2 g of spirulina a day for 12-24 weeks; some studies saw symptoms improve. Certainty of evidence: low.Metabolic syndrome and blood lipids: a few small trials reported slight falls in low-density lipoprotein cholesterol (, the so-called bad cholesterol) and in ; the doses and the size of the effect were inconsistent across trials, and the effects were small. Certainty of evidence: low.Exercise fatigue and antioxidant markers: modest improvements of little clinical importance.Fatty liver, that is, metabolic dysfunction-associated steatotic liver disease — (formerly NAFLD): mainly animal experiments, with only small human studies; large trials are needed to replicate it.
Overall: the mechanism is clear in cells and animals. In people there are only small, short trials that mostly look at lab markers (), the effects are small, and the certainty of the evidence is low. No large multicenter trial has shown a benefit on hard outcomes such as heart attack or death.
Myth · Does a blue latte do anything?
The "blue latte" craze on social media was phycocyanin's entry into the mainstream:Some brands packaged phycocyanin extract as a "magic blue powder" and sold it at a high price.A photogenic blue, plus "superfood, anti-inflammatory, anti-aging" marketing and influencer endorsements, made it take off overnight.A blue latte typically uses 1/2-1 teaspoon (about 1 g) of phycocyanin powder, with plant milk, honey and vanilla.The experience of drinking it: beautiful, with a story, and it feels "healthy".
Looking at the dose:
Human trials fed 1-8 g of dried spirulina a day, which works out to roughly 0.15-1.5 g of phycocyanin. A teaspoon or so of extract powder may, depending on its purity, land at the low end of that range; but the trials used whole spirulina, not purified phycocyanin, and nobody has measured whether a latte has the same effect.On price, it costs far more than half a cup of green tea or a small handful of blueberries."Blue equals healthy" is visual marketing, not a nutritional signal.
The lesson worth keeping: when a food photographs well, carries the right keywords on its label and costs a lot, it is easily taken to be "nutritious". That impression often has little to do with what the food actually does in the body.
In practice: if you like the taste and color of a blue latte, drinking it is fine — that is a pleasure, not a nutrition strategy. Treat it as a pretty drink, not a "superfood beverage".
Money spent on the things that actually move your health (vegetables and fruit, training, sleep) goes much further than money spent on a blue drink.
Chapter 5
Who can buy it, who shouldn't
Most people do not need spirulina. These 5 groups in particular should not buy it:
1. Strict vegans who want it for B12: it will not cover you, and that is a real health risk. Use a B12 supplement or fortified foods instead (see Vitamin B12).
2. Pregnant and breastfeeding women: heavy metals and microcystins pose a greater risk to a fetus or baby, and safety data are scarce.
3. Children under 12: for the same reasons, and at this age nutrition should come first from whole foods.
4. People with autoimmune disease (systemic lupus erythematosus, multiple sclerosis, Hashimoto's thyroiditis): spirulina contains components that can activate the immune system, and case reports describe disease starting or flaring after taking it; how often this happens cannot be estimated.
5. People on anticoagulant or antiplatelet drugs (warfarin, aspirin and others): it contains vitamin K and components that may affect platelets, and the interactions have not been worked out; ask your doctor first.
Overall, spirulina is slightly useful, heavily overhyped, and its risks are often played down. When you hear that "spirulina is a superfood, a cure-all, a must-have", run through the list above first.
1. Strict vegans who want it for B12: it will not cover you, and that is a real health risk. Use a B12 supplement or fortified foods instead (see Vitamin B12).
2. Pregnant and breastfeeding women: heavy metals and microcystins pose a greater risk to a fetus or baby, and safety data are scarce.
3. Children under 12: for the same reasons, and at this age nutrition should come first from whole foods.
4. People with autoimmune disease (systemic lupus erythematosus, multiple sclerosis, Hashimoto's thyroiditis): spirulina contains components that can activate the immune system, and case reports describe disease starting or flaring after taking it; how often this happens cannot be estimated.
5. People on anticoagulant or antiplatelet drugs (warfarin, aspirin and others): it contains vitamin K and components that may affect platelets, and the interactions have not been worked out; ask your doctor first.
Overall, spirulina is slightly useful, heavily overhyped, and its risks are often played down. When you hear that "spirulina is a superfood, a cure-all, a must-have", run through the list above first.
In practice · If you try it: dose and expectations
Narrow situations where it might be considered:You already have the basics in place: a varied whole-food diet, training, sleep and enough protein.You are interested in phycocyanin's anti-inflammatory effect: for example, mild allergic rhinitis or mildly raised blood lipids, and you want to try an over-the-counter option.You are willing to bear the cost: an ongoing monthly expense, plus the heavy-metal and microcystin risks.You will choose a product with third-party certification and published batch test results (for example NSF or USP certification).
Doses used in trials:
Typical randomized trials: 1-8 g of dry powder a day, observed for 4-12 weeks.Allergic rhinitis studies: 1-2 g a day.Blood-lipid studies: the doses varied between trials, and no reliable dose can be given.
The right expectations:
It will not make you 10 years younger.It does not replace vegetables and fruit.It cannot prevent cancer, and it cannot delay aging.It may modestly improve some lab markers (); the clinical difference is small.
On the supplement shelf, it belongs to the group where the marketing and the evidence sit furthest apart.
Background · Why aid programs and space missions use it
Spirulina has a few genuinely reasonable uses that are worth knowing:1. Severe protein-energy malnutrition
Children with acute malnutrition in refugee camps and areas of extreme poverty.Dried spirulina is used as a protein-plus-micronutrient concentrate: 5-15 g a day, together with fortified foods.Some non-governmental organizations (such as IIMSAM) use it for emergency nutrition in parts of Africa and India.The reasoning: when even basic vegetables and protein are lacking, spirulina's nutrient density per gram starts to matter — 1 g of spray-dried powder supplies 0.6 g of protein plus a range of micronutrients.
2. Polar, space and other extreme environments
NASA has studied spirulina as part of a closed-loop food system for long space missions.It is compact, keeps for a long time, and can be regrown under LED light.This is an engineering-constrained situation with no better option.
3. Emergency food-aid packages
The UN Food and Agriculture Organization (FAO) and the World Health Organization have evaluated spirulina in some nutritional emergency protocols.Again, a specific situation of extreme scarcity.
Why these situations are not yours:
You are not in a refugee camp; you can go to a supermarket.You are not on Mars; you can buy eggs, broccoli and fish.Your nutritional bottleneck is not calories and protein per gram but choice, variety and consistency.
So "spirulina helps in refugee camps, therefore it will help me" transplants a conclusion from an extreme situation onto your own. The same molecule brings completely different extra benefit depending on where you start — one of the most common reasoning errors in the supplement world.
If your health problem is "I eat too much processed food, I don't exercise, I don't sleep enough", adding spirulina solves none of it.
Judging a supplement means judging not only the molecule but also the starting point you are in.
References · 5
- Karkos, P. D., Leong, S. C., Karkos, C. D., Sivaji, N., & Assimakopoulos, D. A. (2011). Spirulina in clinical practice: evidence-based human applications. Evidence-Based Complementary and Alternative Medicine, 2011, 531053. 10.1093/ecam/nen058
- 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
- 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
- Ku, C. S., Yang, Y., Park, Y., & Lee, J. (2013). Health benefits of blue-green algae: prevention of cardiovascular disease and nonalcoholic fatty liver disease. Journal of Medicinal Food, 16(2), 103-111. 10.1089/jmf.2012.2468