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
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Blue-green algae, or spirulina, is a rich source of protein, vitamins, minerals, and essential fatty acids. It has been promoted as a weight-loss aid, but this claim has not been proven by research.
Blue-green algae, or spirulina, 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 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 scientific evidence supporting its use for this purpose is weak.
Blue-green algae can be taken as a powder or as flakes, capsules, or tablets. The typical manufacturer’s recommended intake is 2,000–3,000 mg per day divided throughout the day. However, typical amounts shown to have helpful properties in animal studies would be equivalent to 34 grams per day or more, for a 150-pound human.
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.
As it is not an essential nutrient, blue-green algae is not associated with a deficiency state. However, people who do not consume several servings of vegetables per day could benefit from the carotenoids and other nutrients in blue-green algae. Since it is a complete protein, it can be used in place of some of the protein in a healthy diet. However, very large amounts are required to provide significant quantities of these nutrients from blue-green algae.
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.
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]
Last Review: 07-08-2014
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