Spirulina (blue-green algae)

Abstract and key points

Spirulina refers to various species of blue-green algae found naturally in lakes and grown commercially.

It is used as a food colouring and is taken orally as a nutritional supplement in tablet, capsule or dried powder form.

It is claimed to have immune-stimulating effects and to be beneficial in a wide range of diseases including cardiovascular disease, diabetes, viral infections and cancer.

Effects on the immune system have been observed in pre-clinical studies and small trials in healthy volunteers and possible protective effects against chemotherapy toxicity have been reported in animal models. One small clinical trial in leukoplakia reported better response (improvement of lesions) to a year’s treatment with spirulina than to placebo.

Few adverse effects have been reported with spirulina products. Some blue-algae products have been found to be contaminated with hepatotoxic microcystins and will not be as safe as pure spirulina supplements.

Evidence of beneficial effects in cancer is extremely limited but spirulina is generally well-tolerated. Reliable evidence on safety in pregnancy and breast-feeding is not available.


Karen Pilkington, CAM Cancer Consortium. Spirulina (blue-green algae) [online document], August 25, 2020.

Document history

Assessed as up to date in August 2020 by Barbara Wider.

Assessed as up to date in January 2019 by Barbara Wider.
Assessed as up to date in January 2015 by Barbara Wider.
Assessed as up to date in January 2015 by Barbara Wider.
Summary first published in April 2013, authored by Karen Pilkington.

What is it?


Spirulina is a microscopic, filamentous, blue-green algae used as a nutritional supplement. Its name derived from the fact that the filaments are spiral1,2.

Scientific and other names

Scientific names: Spirulina maxima; Spirulina platensis, Spirulina maxima, Spirulina pacifica (also known as Arthrospira platensis, Arthrospira maxima); Brand and common names: Blue Green Algae, Cyanobacteria, SBGA, Spiralyne, Spirulina Blue-Green Algae, Spiruline3.


The constituents of spirulina include protein (50-70%) including all essential amino-acids, essential fatty acids, polysaccharides, B vitamins particularly vitamin B12, beta-carotene and minerals particularly iron1-3.

Application and dosage

Spirulina is taken orally, as capsules, tablets, powder or as flakes either dried or freeze-dried form4. Varied doses have been used in clinical studies; a dose of 1g per day was used to treat oral leukoplakia5 while 400mg/day of an enriched spirulina extract was used to enhance natural killer cell activity in healthy subjects6. Standard doses of 2 to 3g per day have been recommended by manufacturers for a range of conditions4.


Spirulina was originally harvested from lakes in parts of Africa and Mexico, dried and used as a food7. It was reportedly used during the Aztec civilisation2. It still forms an important part of the diet in several parts of the world as a source of protein and because it lacks cellulose cell walls so is easily digested2. It gained prominence more recently after it was used as a dietary supplement for astronauts on space missions8. Commercially, spirulina species are now generally grown under controlled conditions3. In North America, the two most popular species, Spirulina maxima and Spirulina platensis, are cultivated in Mexico and California respectively4. It is also cultivated in Thailand, India, Japan and China1.

Claims of efficacy/Alleged indication(s)

Blue-green algae as a group are used as nutritional supplements due their high protein and vitamin and iron content3. They are also used for promoting weight loss. Spriulina has been used as a general immunostimulant and it has been suggested that it could be taken to prevent and treat cancer and viral infections9. A wide range of other uses have been proposed: these include the treatment of anxiety and depression, attention deficit hyperactivity disorder, cardiovascular disease including raised cholesterol levels, diabetes, fatigue, premenstrual syndrome (PMS), and the promotion of digestion and bowel health3. A review published in 2011 concluded that multiple studies on the efficacy of spirulina in several diseases had been conducted and it may have anticancer, antiviral and anti-allergic effects2.

Mechanism(s) of action

Sprirulina can be used simply as a protein supplements but it is also considered to have specific effects on the immune system although the potential mechanism of action on the immune system is not fully understood. Preliminary studies in healthy humans suggest that spirulina increases the production of the cytokines, tumour necrosis factor, interleukin (IL)-2, and interferon, and causes CD4+ T-helper cell proliferation10,11. It also appears to increase the activity and cytotoxicity of natural killer cells6. Animal studies have demonstrated chemoprotective effects when spirulina is given with various cytotoxic drugs12-14. Several animal studies have investigated the potential of spirulina to have a protective effect against toxicity related to various cytotoxic agents, such as doxorubicin-induced cardiotoxicity13 and cisplatin-induced nephrotoxicity12,14. Beneficial effects have been reported although it is unclear if these findings will translate into clinical use.

Prevalence of use

Spirulina was not among those supplements reported in European surveys on the use of complementary medicine by breast, colorectal or lung cancer patients15-17. Therefore, the prevalence of use in Europe is unclear. It is widely used by cancer populations in South East Asia with surveys revealing it is one of the most frequently used supplements18,19.

Legal issues

Spirulina is widely available as a food and is found as an additive (food colouring) in many foodstuffs. A survey in 2007 revealed that the legal situation regarding spirulina varied across the 27 member states of the European Union, with many countries allowing use as a food supplement, but several restricting or prohibiting use as a food supplement or medicinal use20.

Cost(s) and expenditures

Typical costs for tablets range between £10 and £35 (12 to 30 Euros) per 100 for 500mg tablets while the cost of the powder is in the region of £6 to £8 (8 to 10 Euros) per 100g based on costs advertised on the websites from the UK and Europe in 2013 The cost per day based on the standard dose of 2-3g per day would be 0.75 to 1 Euro per day.

Does it work?

Systematic reviews, meta-analyses

No systematic reviews of spirulina have been published.

Narrative reviews

One review concluded that spirulina species are capable of inhibiting carcinogenesis due to anti-oxidant properties1.

Clinical trials

A clinical trial of 1g/day of Spirulina fusiformis for chemoprevention of oral cancer was reported in 19955. The trial was conducted over the course of 12 months in pan tobacco chewers in Kerala, India who were suffering from oral leucoplakia (a pre-cancerous condition). Complete regression of lesions was observed in 45% (20 of 44 subjects) whose diet was supplemented with spirulina. This compared favourably with those receiving placebo: only 3 of 43 (7%) showed a complete regression in lesions (p < 0.0001). The response appeared to be greater in those with homogeneous lesions. Increased serum concentrations of retinol or beta-carotene were not observed nor was toxicity reported. Sixty people received the spirulina but it appears that the control group was a group who had been randomised to the placebo arm of another study and there were some differences between groups at baseline. Assessment of response was carried out by a physician and a dentist who were unaware of the allocated treatment group but it is unclear to what extent the spirulina and placebo capsules were well-matched. Only the results from those completing the study were included (44 and 43 respectively) in the final analysis. Muscular pain and headaches were reported by 7 and 5 patients taking spirulina and no adverse events were reported by those in the placebo group.

A spirulina product, which apparently has ‘enhanced activity’, was used in a pilot study in the USA in 10 healthy individuals6. After 7 days of the supplement (400mg per day), increased cytotoxic activity of natural killer cells was observed. A separate placebo-controlled study was also conducted. This study involved 11 healthy Danish participants who were randomised to receive 200mg spirulina, 400mg spirulina or placebo daily each for one week with 3.5 week washout periods between treatments6. Enhanced natural killer cell activity was again reported after 7 days treatment. Increased T-cell proliferation and interferon production has also been reported in studies in humans10,11. These studies all suffer from very small numbers of participants (maximum of 12) and were conducted in healthy subjects, therefore the results can only be considered as preliminary.

Is it safe?

Adverse events

Few adverse effects are caused by good quality blue-green algae products (see Warnings)3. Contamination has been reported of some spirulina products which will affect the products’ safety. A recent review of safety by the US Pharmacopeia Dietary Supplements Information Expert Committee considered a total of 31 adverse events reported in relation to spirulina21. Side effects reported in clinical trials include gastro-intestinal problems such as diarrhoea and flatulence3. Headaches and general muscular aches were reported by some patients in one trial although it uncertain whether these were due to spirulina5. One case of anaphylaxis22 and one of acute rhabdomyolysis have also been reported23. The latter resolved after discontinuation of the supplement.


There is a lack of reliable information on safety in pregnancy or breast-feeding3. Long-term use of Spirulina supplements by the mother was found to be related to hypercalcaemia in a newborn baby who developed generalised seizures24.


There is a theoretical interaction between blue-green algae and immunosuppressant drugs due to the possible immune-stimulating effects of the algae3.


Blue-green algae products have been found to be contaminated with potent toxins known as microcystins3,9. Contamination may be more likely for algae grown in natural settings rather than under controlled conditions as is usually the case for commercially available spirulina products3. Microcystins can cause hepatotoxicity, nephrotoxicity and neurotoxicity9 which may be fatal, particularly in children who are more sensitive to the toxic effects3. Symptoms of poisoning including abdominal pain and distention, nausea, vomiting, weakness, excessive thirst, rapid and weak pulse and shock, generally occur between 30 minutes and 24 hours after ingestion3. Recent toxicology studies found some blue-algae products available in Germany and Italy to be contaminated but the affected products were those containing a species other than spirulina25,26. It has been recommended that products should be certified to be free of contamination9.

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  6. Nielsen, C. H., P. Balachandran, O. Christensen, N. D. Pugh, H. Tamta, K. J. Sufka, X. Wu, A. Walsted, M. Schjorring-Thyssen, C. Enevold and D. S. Pasco. Enhancement of natural killer cell activity in healthy subjects by Immulina(R), a Spirulina extract enriched for Braun-type lipoproteins. Planta Med 2010 76(16): 1802-1808. Accessed 15th of September 2020.
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  12. Bhattacharyya, S. and P. Mehta. The hepatoprotective potential of Spirulina and vitamin C supplemention in cisplatin toxicity. Food Funct. 2012 3(2): 164-169. Accessed 15th of September 2020.
  13. Khan, M., J. C. Shobha, I. K. Mohan, M. U. Naidu, C. Sundaram, S. Singh, P. Kuppusamy and V. K. Kutala. Protective effect of Spirulina against doxorubicin-induced cardiotoxicity. Phytother.Res 2005 19(12): 1030-1037. Accessed 15th of September 2020.
  14. Mohan, I. K., M. Khan, J. C. Shobha, M. U. Naidu, A. Prayag, P. Kuppusamy and V. K. Kutala. Protection against cisplatin-induced nephrotoxicity by Spirulina in rats. Cancer Chemother.Pharmacol. 2006 58(6): 802-808. Accessed 15th of September 2020.
  15. Molassiotis A, Fernandez-Ortega P, Pud D, Ozden G, Platin N, Hummerston S, Scott JA, Panteli V, Gudmundsdottir G, Selvekerova S, Patiraki E, Kearney N. Complementary and alternative medicine use in colorectal cancer patients in seven European countries. Complement Ther Med. 2005 Dec;13(4):251-7. Accessed 15th of September 2020.
  16. Molassiotis A, Panteli V, Patiraki E, Ozden G, Platin N, Madsen E, Browall M, Fernandez-Ortega P, Pud D, Margulies A. Complementary and alternative medicine use in lung cancer patients in eight European countries. Complement Ther Clin Pract. 2006 Feb;12(1):34-9. Epub 2005 Nov 14. Accessed 15th of September 2020.
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  22. Petrus M, Culerrier R, Campistron M, Barre A, Rougé P. First case report of anaphylaxis to spirulin: identification of phycocyanin as responsible allergen. Allergy. 2010 Jul;65(7):924-5. Accessed 15th of September 2020.
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