Who Should Not Take Spirulina

Spirulina is sold over the counter and has a reputation as a safe “green” product. However, there are conditions in which taking it is contraindicated or requires a doctor's approval. The editors have broken down the absolute and relative contraindications, explained the mechanism of each restriction, and prepared a short self-check checklist.

Absolute and relative contraindications

In medicine, a distinction is made between absolute contraindications — when intake is unacceptable under any conditions — and relative ones, when the decision is made individually, weighing benefit against risk. For dietary supplements this boundary is less formalized than for drugs, since large-scale registration studies are not conducted for them.

For spirulina the clearest absolute contraindication is phenylketonuria, as well as a confirmed allergy to spirulina or other cyanobacteria. Most other restrictions are relative: autoimmune diseases, taking certain medications, pregnancy, severe kidney and liver disease.

It is important to understand that some contraindications are based on the mechanism of action and individual clinical cases, rather than on large controlled studies. The absence of evidence of harm in such groups does not equal proof of safety — that is exactly why the editors advise a conservative approach.

Below is a summary of the main situations in which taking spirulina is either unacceptable or requires a doctor's consultation. We examine each of them in detail in the following sections.

Phenylketonuria and allergy

Phenylketonuria is a hereditary metabolic disorder in which the body cannot normally convert the amino acid phenylalanine. Its accumulation damages the nervous system, so patients follow a strict diet with restricted protein.

Spirulina is a product with a very high protein content (over half of the dry mass), and therefore of phenylalanine. Even a few grams a day can significantly affect a patient's calculated diet. That is why safety reviews, including the USP, note phenylketonuria as a contraindication.

Allergic reactions to spirulina are rare but have been described — from urticaria to anaphylaxis. For people who have previously had reactions to algae or cyanobacteria supplements, intake is contraindicated. Caution is also needed with pronounced food allergies in general.

If itching, rash, swelling of the lips or face, or difficulty breathing appear after the first intake, use should be stopped immediately, and in case of anaphylaxis symptoms, call emergency services.

Autoimmune diseases and immunosuppression

In experimental and some clinical studies, spirulina enhanced the activity of natural killer cells, the production of interferon, and other immune mediators. For a person with a healthy immune system this is mostly neutral, but in autoimmune conditions the immune system is already attacking its own tissues.

Lee and Werth (2004) described a series of patients in whom autoimmune skin diseases — dermatomyositis and pemphigus — arose or worsened after taking immunostimulating supplements, including spirulina. Causation cannot be proven from such observations, but they became grounds for warnings in professional sources.

• systemic lupus erythematosus;
• rheumatoid arthritis;
• multiple sclerosis;
• psoriasis and psoriatic arthritis;
• autoimmune thyroiditis (discuss with an endocrinologist);
• dermatomyositis, pemphigus, and other autoimmune dermatoses.

A separate case is patients taking immunosuppressants after organ transplantation or to treat autoimmune diseases. In theory, immune stimulation may counteract the therapy. Although there is little clinical evidence of such an interaction, the risk of transplant rejection or disease exacerbation is too serious to experiment with.

For all these groups, the decision to take spirulina should be made by the treating physician — a rheumatologist, immunologist, or transplant specialist.

Medications, pregnancy, and other situations

Warfarin and other vitamin K antagonists are sensitive to fluctuations in the intake of this vitamin from food. Spirulina contains vitamin K, so regularly starting or stopping it can affect the INR. The new oral anticoagulants do not depend on vitamin K as directly, but any supplements taken alongside anticoagulant therapy are best coordinated with a doctor.

During pregnancy and breastfeeding, the main concern is not spirulina itself but possible contamination with microcystins and heavy metals, to which the fetus and infant are especially sensitive. Controlled safety studies in these groups are insufficient, so the editors do not recommend self-directed use.

Children are also more vulnerable to toxins per unit of body weight. Spirulina is sometimes used in nutritional support programs for malnutrition, but this is done under medical supervision and with verified raw material.

With gout and hyperuricemia, it should be remembered that spirulina, like other microorganisms, contains nucleic acids whose breakdown yields uric acid. In severe renal insufficiency, a significant load of protein, phosphorus, and potassium also requires approval from a nephrologist.

People with liver diseases should be cautious because of the described isolated cases of hepatotoxicity associated with spirulina supplements — probably due to contamination.

Checklist before starting

To assess whether spirulina is right for you, the editors suggest taking a short self-check. If you answer “yes” to even one question, consult a doctor before purchasing.

Do you have phenylketonuria or an allergy to algae? Have you been diagnosed with an autoimmune disease? Do you take anticoagulants, immunosuppressants, or other medications regularly? Are you pregnant, planning a pregnancy, or breastfeeding? Do you have gout or kidney or liver disease?

If all the answers are “no,” the next step is choosing a product with laboratory quality control. Even a healthy person is not immune to the risks associated with contaminated raw material.

While taking it, watch for the body's signals: rash, abdominal pain, yellowing of the skin or dark urine, severe muscle weakness — grounds to stop taking it and see a doctor.

Editors' conclusions

The absolute contraindications to spirulina are phenylketonuria and allergy to cyanobacteria. The remaining restrictions are relative and require an individual decision with a doctor.

The most important risk groups are people with autoimmune diseases, patients on immunosuppressants and anticoagulants, pregnant and breastfeeding women, children, patients with gout and kidney or liver disease.

For everyone else, the key safeguard is product quality and a gradual start.

More on the topic in our articles “Spirulina Side Effects,” “Myths About Spirulina,” and “Chlorella Side Effects.”

References

1. 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.
2. Lee AN, Werth VP. Activation of autoimmunity following use of immunostimulatory herbal supplements. Arch Dermatol. 2004;140(6):723–727.
3. 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.
4. Iwasa M, Yamamoto M, Tanaka Y, Kaito M, Adachi Y. Spirulina-associated hepatotoxicity. Am J Gastroenterol. 2002;97(12):3212–3213.
5. Gilroy DJ, Kauffman KW, Hall RA, Huang X, Chu FS. Assessing potential health risks from microcystin toxins in blue-green algae dietary supplements. Environ Health Perspect. 2000;108(5):435–439.
6. Belay A. The potential application of Spirulina (Arthrospira) as a nutritional and therapeutic supplement in health management. J Am Nutraceutical Assoc. 2002;5(2):27–48.