To the Editor.—
A current health food fad involves tablets of Spirulina,1 a genus of blue-green algae belonging to the family Oscillatoriaceae of the division Cyanophyta,2 represented in the health food literature to contain large amounts of vitamin B12.We subjected three popular brands of 500-mg Spirulina tablets to both the United States Pharmacopeia microbiologic assay for vitamin B12 and the vitamin B12 radioassay method we recently applied to multivitamin pills.3The results are given in the Table.Microbiologic assay would lead one to believe that 500-mg Spirulina tablets contain about 0.25 to 1 μg of vitamin B12 per tablet, but radioassays, using R binder to measure the total of (cobalamins plus cobalamin analogues) and intrinsic factor to measure cobalamins alone (ie, "true B12"), suggest that more than 80% of what appears to be "vitamin B12" by microbiologic assay is in fact
Herbert V, Drivas G. Spirulina and Vitamin B12. JAMA. 1982;248(23):3096–3097. doi:10.1001/jama.1982.03330230018017
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