What does Blue-Green Algae do?

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

Spirulina’s vitamin B12 content does not appear to be readily usable by people.² Most health benefits to humans claimed for spirulina and other blue-green algae supplementation are supported by anecdotes rather than scientific research. Test tube and animal studies have demonstrated several properties of large amounts of spirulina or spirulina extracts, including antioxidant,³ antiviral,^{4 5} anticancer,^{6 7 8 9} anti-allergy,^{10 11} immune-enhancing,^{12 13 14} liver-protecting,^{15 16 17} blood vessel-relaxing,¹⁸ and blood lipid-lowering^{19 20} effects.

A small, controlled study found that overweight people taking 8.4 grams per day of spirulina lost an average of three pounds in four weeks compared with one and a half pounds when taking placebo, though this difference was not statistically significant and no effects on blood pressure or serum cholesterol were observed.²¹ A later, controlled trial found a small cholesterol-lowering effect when 4.2 grams of spirulina per day were taken for eight weeks, but serum triglycerides, blood pressure, and body weight were unchanged.²²