Blue-green Algae

Purported Benefits, Side Effects & More

Blue-green Algae

Purported Benefits, Side Effects & More
Blue-green Algae

Common Names

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

For Patients & Caregivers

Tell your healthcare providers about any dietary supplements you’re taking, such as herbs, vitamins, minerals, and natural or home remedies. This will help them manage your care and keep you safe.

What is it?

Blue-green algae have not been shown to treat or prevent cancer, AIDS, 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.

It is important to note that blue-green algae may be contaminated by strains of algae (e.g. Microcystis species) that are toxic.

What are the potential uses and benefits?
  • 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 lower cholesterol

    There is some evidence that spirulina may help lower cholesterol in patients with nephrotic syndrome-induced hyperlipidemia
  • 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.
  • For weight loss

    Small studies show that spirulina may benefit obese and overweight adults by reducing triglyceride levels. But larger studies are needed.

What are the 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.
What else do I need to know?

Research Evidence:




Do Not Take if:

  • You are taking drugs that are substrates of Cytochrome P450: Spirulina inhibits CYP 1A2 and 2E1, and may cause accumulation of drugs metabolized by these enzymes, thereby increasing the risk of their side effects. Clinical relevance is not known.

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 forms to prevent and treat cancer, 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.

Small studies have shown that spirulina may be effective against allergic rhinitis (5); for managing diabetes (3); for lowering cholesterol in patients with nephrotic syndrome-induced hyperlipidemia (4); for relief from chronic pain (23); may benefit obese and overweight adults by reducing obesity indices (24) (28); benefit those with mild cognitive impairment (29); and improve quality of life in ulcerative colitis patients (30). Spirulina may also be effective against chronic hepatitis C virus infection (19) and adjunctive use, against oral lichen planus (31). Foods fortified with spirulina were found to help motor development and prevent morbidity due to upper respiratory infections in infants (25) and positively affect development in children (26).

Supplementation may benefit HIV patients via immunomodulatory effects and by reducing viral load (27). Animal models suggest that spirulina has chemo- and radioprotective effects (6), but human studies are lacking. It is important to note that blue-green algae may be contaminated by strains of algae (e.g. Microcystis species) that are toxic.

Purported Uses and Benefits
  • 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).

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). Clinical relevance is not known.
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. Zhang H, et al. Chemo- and radio-protective effects of polysaccharide of Spirulina platensis on hemopoietic system of mice and dogs. Acta Pharmacol Sin. 2001;22:1121-4.
  7. Premkumar K. et al. Effect of Spirulina fusiformis on cyclophosphamide and mitomycin-C induced genotoxicity and oxidative stress in mice. Fitoterapia 2001;72:906-11.
  8. Mathew B, et al. Evaluation of chemoprevention of oral cancer with Spirulina fusiformis. Nutr Cancer 1995;24:197-202.
  9. Draisci R, et al. Identification of anatoxins in blue-green algae food supplements using liquid chromatography-tandem mass spectrometry. Food Addit Contam 2001;18:525-31.
  10. Patocka J. The toxins of Cyanobacteria. Acta Medica 2001;44:69-75.
  11. Iwasa M, Yamamoto M, Tanaka Y, Kaito M, Adachi Y. Spirulina-associated hepatotoxicity. Am.J Gastroenterol. 2002;97:3212-3.
  12. 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.
  13. 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.
  14. 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.
  15. Hayashi T, et al. Calcium spirulan, an inhibitor of enveloped virus replication, from a blue-green algae Spirulina platensis. J Nat Prod 1996;59:83-7.
  16. 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.
  17. 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.
  18. 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.
  19. Yakoot M, Salem A. Spirulina platensis versus silymarin in the treatment of chronic hepatitis C virus infection. A pilot randomized, comparative clinical trial. BMC Gastroenterol. 2012 Apr 12;12:32.
  20. Savranoglu S, Tumer TB. Inhibitory effects of spirulina platensis on carcinogen-activating cytochrome P450 isozymes and potential for drug interactions. Int J Toxicol. 2013 Sep-Oct;32(5):376-84.
  21. 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.
  22. 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.
  23. Jensen GS, Drapeau C, Lenninger M, Benson KF. Clinical Safety of a High Dose of Phycocyanin-Enriched Aqueous Extract from Arthrospira (Spirulina) platensis: Results from a Randomized, Double-Blind, Placebo-Controlled Study with a Focus on Anticoagulant Activity and Platelet Activation. J Med Food. 2016 Jul;19(7):645-53.
  24. Yousefi R, Mottaghi A, Saidpour A. Spirulina platensis effectively ameliorates anthropometric measurements and obesity-related metabolic disorders in obese or overweight healthy individuals: A randomized controlled trial.Complement Ther Med. 2018 Oct;40:106-112.
  25. Masuda K, Chitundu M. Multiple micronutrient supplementation using spirulina platensis and infant growth, morbidity, and motor development: Evidence from a randomized trial in Zambia. PLoS One. 2019 Feb 13;14(2):e0211693.
  26. Masuda K, Chitundu M. Multiple Micronutrient Supplementation Using Spirulina platensis during the First 1000 Days is Positively Associated with Development in Children under Five Years: A Follow up of A Randomized Trial in Zambia. Nutrients. 2019 Mar 29;11(4). pii: E730.
  27. Ngo-Matip ME, Pieme CA, Azabji-Kenfack M, et al. Impact of daily supplementation of Spirulina platensis on the immune system of naïve HIV-1 patients in Cameroon: a 12-months single blind, randomized, multicenter trial. Nutr J. 2015 Jul 21;14:70.
  28. Zarezadeh M, Faghfouri AH, Radkhah N, et al. Spirulina supplementation and anthropometric indices: A systematic review and meta-analysis of controlled clinical trials. Phytother Res. 2021 Feb;35(2):577-586.
  29. Choi WY, Lee WK, Kim TH, et al. The Effects of Spirulina maxima Extract on Memory Improvement in Those with Mild Cognitive Impairment: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial. Nutrients. 2022 Sep 9;14(18):3714.
  30. Moradi S, Zobeiri M, Feizi A, Clark CCT, Entezari MH. The effects of spirulina (Arthrospira platensis) supplementation on anthropometric indices, blood pressure, sleep quality, mental health, fatigue status and quality of life in patients with ulcerative colitis: A randomised, double-blinded, placebo-controlled trial. Int J Clin Pract. 2021 Oct;75(10):e14472.
  31. Chaitanya NC, Chikte D, Kumar YP, et al. Efficacy of Spirulina 500 mg vs Triamcinolone Acetonide 0.1% for the Treatment of Oral Lichen Planus: A Randomized Clinical Trial. J Contemp Dent Pract. 2022 May 1;23(5):552-557.
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