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.
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.
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.
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.
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.
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.
Attention deficit hyperactivity disorder
HIV and AIDS
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.
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)
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).
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.
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.