Q & A Library

Vitamin B12, also known as cyanocobalamin, is a water-soluble vitamin that is part of the B complex. It helps support adrenal function as well as maintain a healthy nervous system. B12 is also involved in bone marrow activity, DNA synthesis, and other key metabolic processes.

All of the vitamin B12 in our diets must come from animal foods. For this reason, deficiencies can develop among strict vegetarians, especially vegan children. B12 deficiency is also common among older people, who lose the ability to absorb it from the stomach. Pregnant women and those who suffer from GI disorders are also at higher risk.

Vitamin B12 depletion also can occur in those who drink too much alcohol, as well as some patients on long-term antibiotic therapy and other prescribed drugs, such as stomach-acid-suppressants (H-2 blockers and proton pump inhibitors) and the diabetes drug, metformin. Nicotine can also lower serum levels of B12.

The Recommended Dietary Allowance (RDA) for B12 for people age 14 and older is 2.4 mcg a day; for adult and adolescent pregnant females, 2.6 mcg; and for adult and adolescent lactating females, 2.8mcg. Individuals over 50 years of age should consume vitamin B12-fortified foods, or take a vitamin B12 supplement - 25-100 mcg per day has been used to maintain vitamin B12 levels in older people. I recommend taking 50 mcg as part of a B-Complex that contains a full spectrum of B vitamins, including biotin, thiamine, B12, riboflavin and niacin.

The two forms of B12 supplements you ask about are tablets and sprays. Although both are effective, for those who are concerned about an actual deficiency, I often recommend the sprays (such as "Spray For Life"); spritzing them under your tongue results in much better absorption than swallowing a pill. Spray forms of supplemental B12 may be particularly useful for seniors, who might not otherwise be able to absorb the vitamin from food or tablets.

Andrew Weil, M.D.