Myths About Spirulina

A whole layer of mythology has formed around spirulina: it is called “the food of astronauts,” “the most complete product on Earth,” and a remedy for dozens of diseases. Some of these claims have a kernel of truth, some are pure marketing. The editors have checked the most common myths against clinical study data and systematic reviews.

Myths 1–2: spirulina is a superfood that replaces a full diet

A popular claim: “spirulina contains all the nutrients you need and can replace ordinary food.” Indeed, per gram of dry mass it is very nutritious: 55–70% protein, iron, beta-carotene, B vitamins, gamma-linolenic acid. But the key word is “per gram.”

A real serving of spirulina is 3–6 g per day. In that amount it provides 2–4 g of protein, part of the daily requirement for iron and provitamin A — and adds almost nothing to calories, fiber, calcium, or vitamin C. Comparing “100 g of spirulina” with “100 g of beef” is incorrect, since no one eats 100 g of spirulina a day.

The second myth is that “spirulina is a complete protein replacement.” Spirulina's amino acid profile is decent, although its methionine and cysteine content is relatively low compared with animal proteins. But the main thing is that to get 25 g of protein you would need about 40 g of spirulina, which is several times the doses from studies and would most likely cause gastrointestinal discomfort.

The editors' verdict: spirulina is a useful addition to the diet, but not a replacement for a varied diet and not an alternative to protein supplements.

Myth 3: spirulina is a reliable source of vitamin B12

This myth is perhaps the most harmful, because it concerns vegans and vegetarians, for whom B12 deficiency is a real threat. Labels often list a high content of “vitamin B12,” and people forgo separate supplements.

Studies by Watanabe's group showed that the overwhelming majority of the compounds identified as B12 in spirulina are pseudovitamin B12 (adenylcobamide). It gives a positive result in some analytical methods but is inactive in the human body.

Moreover, there are concerns that the pseudovitamin may compete with active B12 for transport proteins, although the clinical significance of this effect has not been established. In any case, spirulina cannot be relied on as a source of B12.

Verdict: a myth. Vegans need verified sources — cyanocobalamin or methylcobalamin supplements and fortified foods — and B12 levels should be monitored with tests.

Myth 4: spirulina “removes toxins” and “cleanses the body”

The concept of “detox” is one of the most successful marketing ideas in the supplements field. It is claimed that spirulina “binds toxins,” “removes heavy metals,” and “cleanses the liver.” In reality the notion of “toxins” [as in slag/waste] has no medical meaning, and the neutralization of substances in the body is handled by the liver and kidneys.

There are laboratory and small clinical studies on the effect of spirulina on the accumulation of arsenic or other metals, but they are insufficient for recommendations, and treating heavy metal poisoning is a task for a toxicologist, not a supplement.

The paradox is that spirulina itself, through microalgae's ability to bind metals, can be a source of lead, cadmium, or arsenic if grown in a contaminated environment. A “detox product” of dubious quality is more likely to add toxins than to remove them.

Verdict: mostly a myth. The supplement does not replace the normal work of the liver and kidneys, and the quality of the raw material is far more important than marketing promises.

Myths 5–6: spirulina burns fat and cures diseases

Spirulina is often positioned as a weight-loss aid. The meta-analysis by Moradi et al. (2019) of randomized studies found a statistically significant but small reduction in body weight, especially in people with obesity. This refers to a kilogram or two over several months — an effect easily offset by any dietary error.

More serious data concern the lipid profile: the meta-analysis by Serban et al. (2016) showed a reduction in total cholesterol, LDL, and triglycerides and an increase in HDL. This is an interesting result, but the studies were small and heterogeneous, and spirulina does not replace statins when they are indicated.

Claims about “curing” cancer, diabetes, AIDS, and other diseases are based mainly on laboratory experiments on cells and animals. In a test tube phycocyanin does indeed exhibit antioxidant and anti-inflammatory properties, but between the test tube and treating a human there is a gulf that no one has yet crossed.

Verdict: partly true regarding lipids, an exaggeration regarding weight loss, a myth regarding the treatment of serious diseases.

Myth 7: “natural means safe for everyone”

The last myth concerns safety. Spirulina does indeed have a favorable profile, as confirmed by the USP assessment. However, “naturalness” does not cancel out contraindications and risks.

Spirulina is contraindicated in phenylketonuria and requires caution in autoimmune diseases and while taking anticoagulants or immunosuppressants. Rare cases of allergy, hepatotoxicity, and rhabdomyolysis have been described, some of which are linked to contaminated raw material.

Another common myth is that spirulina and chlorella are “the same thing.” Spirulina is a cyanobacterium, a prokaryote; chlorella is a true green alga with a cell wall. They differ in composition, manufacturing, and studied effects.

Verdict: a myth. Spirulina is safe for most healthy adults provided the raw material is of good quality and the doses are reasonable, but not for everyone and not under any conditions.

Editors' conclusions

Spirulina is a nutritious addition to the diet with moderately convincing data on the lipid profile and limited data on endurance.

It does not replace a full diet or protein, is not a reliable source of vitamin B12, does not “remove toxins,” and does not cure oncological diseases.

Realistic expectations and a quality product are the best protection against disappointment and against the risks.

To get the full picture, also read “How to Take Spirulina,” “Who Should Not Take Spirulina,” and “Chlorella: What It Is and How It Works.”

References

1. Watanabe F. Vitamin B12 sources and bioavailability. Exp Biol Med (Maywood). 2007;232(10):1266–1274.
2. Serban MC, Sahebkar A, Dragan S, et al. A systematic review and meta-analysis of the impact of Spirulina supplementation on plasma lipid concentrations. Clin Nutr. 2016;35(4):842–851.
3. Moradi S, Ziaei R, Foshati S, et al. Effects of Spirulina supplementation on obesity: a systematic review and meta-analysis of randomized clinical trials. Complement Ther Med. 2019;47:102211.
4. Kalafati M, Jamurtas AZ, Nikolaidis MG, et al. Ergogenic and antioxidant effects of spirulina supplementation in humans. Med Sci Sports Exerc. 2010;42(1):142–151.
5. Marles RJ, Barrett ML, Barnes J, et al. United States Pharmacopeia safety evaluation of Spirulina. Crit Rev Food Sci Nutr. 2011;51(7):593–604.
6. Karkos PD, Leong SC, Karkos CD, Sivaji N, Assimakopoulos DA. Spirulina in clinical practice: evidence-based human applications. Evid Based Complement Alternat Med. 2011;2011:531053.
7. Deng R, Chow TJ. Hypolipidemic, antioxidant, and antiinflammatory activities of microalgae Spirulina. Cardiovasc Ther. 2010;28(4):e33–e45.