Some vegetarians and vegans use the green algaes as a Vitamin B12 source. I just searched the web and found several websites claiming that both spirulina and blue-green algae are great sources of B12. They are correct. Partially. In fact they do contain adequate amounts of B12, but it is also contains pseudo-B12. Pseudo-B12 is an analog of the actual cobalamin molecule so it will unfortunately inhibit B12 utilization in the body.
How does it inhibit B12 utilization? It competes with the active B12 and binds itself to the receptor, yet the pseudo-B12 has no active component so the body cannot use it. Thus a vegan or perhaps a vegetarian can develop a B12 deficiency or worse a deficiency by using these ‘super-foods’ containing high amounts of pseudo-B12. I advise vegans and vegetarians not to use blue-green algae or spirulina to supplement their diet. However chlorella has been shown to contain a larger percentage of active B12 and may be used as supplementation. The best B12 supplementation for a vegan or vegetarian are supplements in its natural form – methylcobalamin or hydroxycobalamin are often suggested. (cynocobalamin is the ubiquitous synthetic form)
See the following sources:
Pseudovitamin B(12) is the predominant cobamide of an algal health food, spirulina tablets., J Agric Food Chem. 1999 Nov;47(11):4736-41
Purification and characterization of a corrinoid-compound in an edible cyanobacterium Aphanizomenon flos-aquae as a nutritional supplementary food. J Agric Food Chem. 2006 Dec 13;54(25):9604-7
Purification and characterization of corrinoid-compounds from the dried powder of an edible cyanobacterium, Nostoc commune (Ishikurage).J Nutr Sci Vitaminol (Tokyo). 2007 Apr;53(2):183-6
Characterization and bioavailability of vitamin B12-compounds from edible algae.J Nutr Sci Vitaminol (Tokyo). 2002 Oct;48(5):325-31.
Dried Green and Purple Lavers (Nori) Contain Substantial Amounts of Biologically Active Vitamin B12 but Less of Dietary Iodine Relative to Other Edible SeaweedsJ. Agric. Food Chem., 47 (6), 2341 -2343, 1999.
In Health,
George Mandler
Licensed Acupuncturist
Licensed Dietitian Nutritionist
Certified Nutrition Specialist
Diplomat Oriental Medicine