What is it? Overview Usage Side Effects and Warnings

Spirulina Side Effects and Warnings

Written by FoundHealth.

Safety Issues

Spirulina itself appears to be nontoxic. 1 Studies in rats showed that high spirulina intake caused no weight reduction or toxicity symptoms in rats, nor did spirulina affect the rats' ability to reproduce normally. 2 Nevertheless, there are areas of serious concern for consumers.

Various forms of blue-green algae can be naturally contaminated with highly toxic substances called microcystins. 3 Some states, such as Oregon, require producers to strictly limit the concentration of microcystins in blue-green algae products, but the same protections cannot be assumed to have been applied to all products on the market. Furthermore, the maximum safe intake of microcystins is not clear, and it is possible that when blue-green algae is used for a long time, toxic effects might build up. Long-term use by children raises particular concerns, especially in light of the widely popularized, but unsubstantiated belief, that blue-green algae is useful for attention deficit disorder.

Blue-green algae can also contain a different kind of highly toxic substance, called anatoxin. 4 In addition, when spirulina is grown with the use of fermented animal waste fertilizers, contamination with dangerous bacteria could occur. 5 There are also concerns that spirulina might concentrate radioactive ions found in its environment. 6 Probably of most concern is spirulina's ability to absorb and concentrate heavy metals such as lead and mercury if they are present in its environment. One study of spirulina samples grown in a number of locations found them to contain an unacceptably high content of these toxic metals. 7 However, a second study on this topic claims that the first used an unreliable method of analyzing heavy metal content, 8 and concludes that a person would have to eat more than 77 g daily of the most heavily contaminated spirulina to reach unsafe mercury and lead consumption levels.

These researchers, however, go on to suggest that it is not prudent to eat more than 50 g of spirulina daily. The reason they give is that the plant contains a high concentration of nucleic acids, substances related to DNA. When these are metabolized, they create uric acid, which could cause gout or kidney stones. This is of special concern to those who have already had uric acid stones or attacks of gout.

The safety of spirulina in pregnant and nursing women, young children, and individuals with kidney or liver disease has not been determined.


  1. Dillon JC, Phuc AP, Dubacq JP. Nutritional value of the alga spirulina. World Rev Nutr Diet. 1995;77:32-46.
  2. Salazar M, Chamorro GA, Salazar S, et al. Effect of Spirulina maxima consumption of reproduction and peri- and postnatal development in rats. Food Chem Toxicol.1996;34:353-359.
  3. Pouria S, de Andrade A, Barbosa J, Cavalcanti RL, Barreto VT, Ward CJ, Preiser W, Poon GK, Neild GH, Codd GA. Fatal microcystin intoxication in haemodialysis unit in Caruaru, Brazil. Lancet. 352(9121):21-6.
  4. Astrachan NB, Archer BG, Hilbelink DR. Evaluation of the subacute toxicity and teratogenicity of anatoxin-a. Toxicon. 18(5-6):684-8.
  5. Facts and Comparisons. Spirulina Monograph. The Review of Natural Products.February 1998.
  6. Facts and Comparisons. Spirulina Monograph. The Review of Natural Products.February 1998.
  7. Johnson PE, Shubert LE. Accumulation of mercury and other elements by Spirulina (Cyanophyceae). Nutr Rep Int. 1986;34:1063-1070.
  8. Slotton DG, Goldman CR, Franke A. Commercially grown spirulina found to contain low levels of mercury and lead. Nutr Rep Int. 1989;40:1165-1171.


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