Vitamin B12 (Methylcobalamin / Cyanocobalamin)

Also known as: methylcobalamin, cyanocobalamin, cobalamin, mB12

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In plain English

Vitamin B12 is an essential vitamin needed for healthy nerves, red blood cells, and energy metabolism. Injections and troches are used to correct or prevent deficiency and are commonly added to weight-loss and "energy" blends. In people who are truly deficient, replacing B12 clearly helps; adding it for energy or weight loss in people who aren't deficient has little proven benefit. It is very safe, since excess is excreted in urine.

The science

Vitamin B12 (cobalamin) is a cofactor for methionine synthase and methylmalonyl-CoA mutase, essential for DNA synthesis, hematopoiesis, and myelin maintenance. Deficiency causes megaloblastic anemia and potentially irreversible neurologic disease and is best confirmed with methylmalonic acid/homocysteine when serum B12 is borderline; both parenteral and high-dose oral cobalamin are effective repletion (Stabler, NEJM 2013). Methylcobalamin and cyanocobalamin are common forms used in injections, troches, and combination products. In replete individuals, B12 supplementation for "energy" or weight loss has minimal evidence. It has an excellent safety profile.

References

• Stabler SP, N Engl J Med 2013 (Clinical Practice: Vitamin B12 Deficiency)