Blue-green Algae
Blue-green Algae
This information describes the common uses of Blue-green Algae, how it works, and its possible side effects.

Common Name

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

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.