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-lowering19 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

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.

Blue-green algae have been used in connection with the following conditions (refer to the individual health concern for complete information):