Patients who have received vitamin B12 injections to aid in weight loss tell me they are effective. Since vitamin B12 is water-soluble, is there any harm in getting these injections? What would the mechanism be for weight loss?
—Suzanne Ware, MD, Bakersfield, Calif.

There is no good evidence at this time for giving vitamin B12 to promote weight loss, but there is certainly no harm in it, either. If your patients have noted weight loss on B12, it is possible they had a deficiency and adequate levels helped with their energy levels or mood. (Or it could just be that good old placebo effect.) Currently, the only weight loss-associated indication for routine B12 administration is status post gastric bypass surgery. A recent small study found that levels of homocysteine can increase with weight loss, and replacement with an oral vitamin preparation made of B12/B6/folate can “protect against increased homocysteine production during weight reduction” (Res Exp Med [Berl]. 1998;198:37-42).
—Susan Kashaf, MD, MPH (112-21)

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