Blue-green Algae

Blue-green Algae

Common Names

  • Spirulina platensis
  • Spirulina fusiformis
  • AFA-algae; Arthrospira platensis; Tecuitlatl; BGA

For Patients & Caregivers

How It Works

Blue-green algae has not been shown to treat or prevent cancer, HIV, attention deficit hyperactivity disorder (ADHD), or other serious medical conditions.

Blue-green algae are a natural source of protein and vitamins, which may reduce fatigue. Blue-green algae products usually contain either AFA-algae (Aphanizomenon flos aquae) or Spirulina species, or both. Both may have biological activity. In laboratory experiments, calcium spirulan, an extract from Spirulina, stopped doubling of HIV virus, herpes simplex virus, cytomegalovirus, and influenza virus, but it is not known whether any of these effects would occur in the human body. Other studies showed that spirulina protected lab animals from genetic mutations caused by chemicals and radiation, but again, it is unclear whether these effects happen in humans. In healthy humans, AFA-algae appear to increase blood levels of natural killer cells (a type of immune cell). AFA-algae also show anti-viral and anti-mutation activity in the laboratory.

Spirulina algae also contain high levels of gamma-linolenic acid (GLA), an essential fatty acid that is often able to prevent the accumulation of cholesterol in the body.

Purported Uses
  • As an appetite suppressant
    No scientific evidence supports this use.
  • To treat ADHD (attention deficit hyperactivity disorder)
    There are no data to back this claim.
  • To prevent and treat cancer
    Laboratory studies show that blue-green algae may help protect against DNA mutations.
  • To prevent and treat fatigue
    Scientific evidence is lacking to support this claim.
  • To treat HIV and AIDS
    Blue-green algae show anti-viral activity in the laboratory.
  • To stimulate the immune system
    One study in healthy humans showed that AFA-algae increased blood levels of natural killer cells (immune cells). There is no evidence that such effects help the body fight infections or maintain health.
  • To treat viral infections
    Blue-green algae show anti-viral activity in the laboratory. Human studies are needed.
Research Evidence




Patient Warnings
  • Although it is uncommon, the algae used in Spirulina products may be contaminated with toxins from the Microcystis species. For example, anatoxin and saxitoxin are harmful to the nervous system, causing serious side effects like paralysis of the respiratory system.
Side Effects
  • Anaphylaxis (serious allergic reaction)
    Case Report: A 28-year-old man developed acute rhabdomyolysis (severe muscle weakness and pain) after taking Spirulina supplements for one month. His symptoms resolved after discontinuing supplement use.
    Case Report: A day-old baby was hospitalized for generalized seizures associated with hypercalcemia (high levels of calcium in blood), found to be related to the mother’s long-term consumption of Spirulina supplements.
  • In rare cases, cyanotoxin (e.g. anatoxin, saxitoxin, microcystins) contamination of may cause liver damage, kidney failure, neurological damage, seizures, respiratory arrest, acute pancreatitis (inflammation of pancreas), and damage to the muscles of the heart.
Special Point

Blue-green algae are used a source of food in some parts of the world. Consumption of this product appears to be relatively safe, when not contaminated with Microcystis species.

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For Healthcare Professionals

Scientific Name
Spirulina sp., Aphanizomenon flos-aquae
Clinical Summary

Blue-green algae, also known as Cyanobacteria, are primitive autotrophic prokaryotes. They are a source of food in some parts of the world and patients take the supplemental form to prevent and treat cancer and viral infections, and for weight loss. Spirulina species are cultured in alkaline fresh water whereas Aphanizomenon flos aquae (AFA) is naturally grown and harvested from Upper Klamath Lake, Oregon, USA. Blue-green algae products frequently contain one or both of these strains of algae.

Studies have shown that spirulina may be effective against allergic rhinitis (5), for managing diabetes (3), and for lowering cholesterol in patients with nephrotic syndrome-induced hyperlipidemia (4). Preliminary data indicate that it may also be a safe and effective agent in the treatment of chronic hepatitis C virus infection (19).

Animal studies suggest that spirulina has chemo- and radioprotective effects (6), but human data are lacking.

However, blue-green algae may be contaminated by strains of algae (e.g. Microcystis species) that are toxic.

Purported Uses
  • Appetite suppression
  • ADHD
  • Cancer
  • Fatigue
  • High cholesterol
  • HIV and AIDS
  • Immunostimulation
  • Viral infections
  • Weight loss
Mechanism of Action

Calcium spirulan, a polysaccharide extract from Spirulina platensis, demonstrates inhibition of HIV-1 viral replication via possible binding and disruption of CD4-gp120 interaction in vitro, although the clinical significance of this is unknown (15). Calcium spirulan also inhibits replication of herpes simplex I, cytomegalovirus, and influenza.

Other studies showed that spirulina has chemoprotective and radioprotective effects in animals (6), affected by stimulation of the hemopoietic system.

Although uncommon, several toxins from Microcystis species of algae may contaminate AFA-algae and Spirulina algal blooms. Anatoxin can cause paralysis of respiratory muscles due to irreversible binding and sustained action of the nicotinic acetylcholine receptor. Saxitoxin contamination is thought to block nerve cell neuronal transmission due to binding to voltage-gated sodium channels. Microcystins are cyclic heptapeptides that induce hepatotoxicity (9) (10).

Spirulina can significantly inhibit cytochrome P450 1A2 and 2E1 enzymes. The same study showed that it also led to significant increase in mRNA/protein levels of CYP2B1 and CYP3A1, but there was no change in the enzyme activities (20).

Spirulina was shown to antagonize glioma cell growth in mice by down-regulating angiogenesis, which was mediated in part by regulating the production of interleukin (IL-17) (21).


Microcystin contamination can cause hepatotoxicity, renal failure, and neurotoxicity. Products should be certified that they are free of contaminants.

Adverse Reactions

Anaphylaxis (16) (22)
Case Report: A 28-year-old man developed acute rhabdomyolysis after ingesting Spirulina supplements for one month. His symptoms resolved after discontinuing supplement use (17).
Case Report: A day-old baby was hospitalized for generalized seizures associated with hypercalcemia, found to be related to the mother’s long-term consumption of Spirulina supplements (18).
Cyanotoxin (e.g. anatoxin, saxitoxin, microcystins) contamination of AFA-algae and possibly Spirulina may cause hepatotoxicity, renal failure, neurotoxicity, seizures, respiratory arrest, acute pancreatitis, and cardiomyopathy.
 (2) (6) (9)

Herb-Drug Interactions
  • Cytochrome P450 substrates: Spirulina inhibits CYP 1A2 and 2E1, and may cause accumulation of drugs metabolized by these enzymes, thereby increasing the risk of their side effects (20).
Dosage (OneMSK Only)
  1. Selmi C, Leung PS, Fischer L, et al. The effects of Spirulina on anemia and immune function in senior citizens. Cell Mol Immunol. 2011 Jan 31.

  2. Kalafati M, Jamurtas AZ, Nikolaidis MG, et al. Ergogenic and antioxidant effects of spirulina supplementation in humans. Med Sci Sports Exerc. 2010 Jan;42(1):142-51.

  3. Lee EH, Park JE, Choi YJ, Huh KB, Kim WY. A randomized study to establish the effects of spirulina in type 2 diabetes mellitus patients. Nutr Res Pract. 2008 Winter;2(4):295-300.

  4. Samuels R, Mani UV, Iyer UM, Nayak US. Hypocholesterolemic effect of spirulina in patients with hyperlipidemic nephrotic syndrome. J Med.Food 2002;5:91-6.

  5. Cingi C, Conk-Dalay M, Cakli H, Bal C. The effects of spirulina on allergic rhinitis. Eur Arch Otorhinolaryngol. 2008 Oct;265(10):1219-23.

  6. Mathew B, et al. Evaluation of chemoprevention of oral cancer with Spirulina fusiformis. Nutr Cancer 1995;24:197-202.

  7. Patocka J. The toxins of Cyanobacteria. Acta Medica 2001;44:69-75.

  8. Iwasa M, Yamamoto M, Tanaka Y, Kaito M, Adachi Y. Spirulina-associated hepatotoxicity. Am.J Gastroenterol. 2002;97:3212-3.

  9. Foster S, Tyler VE. Tyler’s Honest Herbal: A Sensible Guide to the Use of Herbs and Related Remedies 4th ed. New York: Haworth Herbal Press; 1999.

  10. Ziegler R. Aphanizomenon flow-Aquae (AFA-Algae). A food supplement with dubious health claims. Meeting of the Swiss Study Group for Complementary and Alternative Methods in Cancer. Weiskirchen (Switzerland): November 9, 2001.

  11. Ayehunie S, et al. Inhibition of HIV-1 replication by an aqueous extract of Spirulina platensis (Arthrospira platensis). J Acquir Immune Defic Syndr Hum Retrovirol 1998;18:7-12.

  12. 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.

  13. Mazokopakis EE, Karefilakis CM, Tsartsalis AN, Milkas AN, Ganotakis ES. Acute rhabdomyolysis caused by Spirulina (Arthrospira platensis). Phytomedicine. 2008 Jun;15(6-7):525-7.

  14. Moulis G, Batz A, Durrieu G, Viard C, Decramer S, Montastruc JL. Severe neonatal hypercalcemia related to maternal exposure to nutritional supplement containing Spirulina. Eur J Clin Pharmacol. 2012 Feb;68(2):221-2.

  15. Kawanishi Y, Tominaga A, Okuyama H, et al. Regulatory effects of Spirulina complex polysaccharides on growth of murine RSV-M glioma cells through Toll-like receptor 4. Microbiol Immunol. 2013 Jan;57(1):63-73.

  16. Le TM, Knulst AC, Röckmann H. Anaphylaxis to Spirulina confirmed by skin prick test with ingredients of Spirulina tablets. Food Chem Toxicol. 2014 Dec;74:309-10.

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