Blue-Green Algae for Weight Control

Also known as: Spirulina

What is it?

Blue-green algae, of which spirulina is a well-known example, is a group of 1,500 species of microscopic aquatic plants. The two most common species used for human consumption are Spirulina maxima and Spirulina platensis. Spirulina is particularly rich in protein and also contains carotenoids, vitamins, minerals, and essential fatty acids.¹

Where is it found?

Blue-green algae grow in some lakes, particularly those rich in salts, in Central and South America, and Africa. They are also grown in outdoor tanks specifically to be harvested for nutritional supplements.

Why do dieters use it?*

Some dieters say that blue-green algae

helps satisfy appetite.
supplies good nutrition while dieting.

What do the advocates say?*

Blue-green algae (spirulina) is a concentrated source of nutrients compared to most foods, but it is expensive compared to other supplemental sources of protein, vitamins, and minerals. Research is limited, but nonetheless has found little benefit of spirulina to dieters.

How much is usually taken by dieters?

Blue-green algae is a rich source of protein, vitamins, minerals, and essential fatty acids. In one double-blind trial, overweight people who took 2.8 grams of blue-green algae as spirulina three times per day for four weeks experienced only small and statistically nonsignificant weight loss.² Thus, although spirulina has been promoted as a weight-loss aid, the current scientific evidence supporting its use for this purpose is weak.

Are there any side effects or interactions?

Few side effects have been reported from the ingestion of blue-green algae. However, as blue-green algae can accumulate heavy metals from contaminated water, consuming blue-green algae could increase the body’s load of lead, mercury, and cadmium,³ though noncontaminated blue-green algae have been identified.⁴ Another popular species of blue-green algae, Aphanizomenon flos-aquae, has been found to produce toxins.⁵ A few reports also describe allergic reactions to blue-green algae. Animal studies have found spirulina to be safe during pregnancy.⁶ ⁷ ⁸

There is one case report of a man who developed liver damage while taking spirulina.⁹ As he was also talking three prescription medications, it is not clear whether the spirulina caused or contributed to the liver injury.

At the time of writing, there were no well-known drug interactions with blue-green algae.

Resources

See a list of books, periodicals, and other resources for this and related topics.

*Dieters and weight-management advocates may claim benefits for blue-green algae based on their personal or professional experience. These are individual opinions and testimonials that may or may not be supported by controlled clinical studies or published scientific articles on blue-green algae. For more complete and detailed information, including references and safety information, see Blue-Green Algae as a nutritional supplement.

References
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1. Dillon JC, Phuc AP, Dubacq JP. Nutritional value of the alga Spirulina. World Rev Nutr Diet 1995;77:32-46.

2. Becher EW, Jakober B, Luft D, et al. Clinical and biochemical evaluations of the alga spirulina with regard to its application in the treatment of obesity. A double-blind cross-over study. Nutr Rep Intl 1986;33:565–73.

3. Johnson PE, Shubert LE. Accumulation of mercury and other elements by spirulina (cyanophyceae). Nutr Rep Int 1986;34:1063–70.

4. Slotton DG, Goldman CR, Franke A. Commercially grown spirulina found to contain low levels of mercury and lead. Nutr Rep Int 1989;40:1165–72.

5. Elder GH, Hunter PR, Codd GA. Hazardous freshwater cyanobacteria (blue-green algae). Lancet 1993;341:1519–20 [letter].

6. Salazar M, Chamorro GA, Salazar S, et al. Effect of Spirulina maxima consumption on reproduction and peri- and postnatal development in rats. Food Chem Toxicol 1996;34:353–9.

7. Kapoor R, Mehta U. Effect of supplementation of blue green alga (Spirulina) on outcome of pregnancy in rats. Plant Foods Hum Nutr 1993;43:29–35.

8. Chamorro G, Salazar M. Teratogenic study of Spirulina in mice. Arch Latinoam Nutr 1990;40:86–94 [in Spanish].

9. Iwasa M, Yamamoto M, Tanaka Y, et al. Spirulina-associated hepatotoxicity. Am J Gastroenterol 2002;97:3212–3. [Letter]

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The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or chemist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires March 2007.