Drug Profile

Vitamin B₁₂, also called cyanocobalamin, is essential for cell growth and normal formation of blood cells. It is found in several kinds of foods (see box above), and a well-balanced diet with a variety of healthful foods should supply all the vitamin that your body needs. The recommended dietary allowance (RDA) of vitamin B₁₂ for older adults is 2.4 micrograms per day.

Even if you do not get enough vitamin B₁₂ in your diet, a vitamin B₁₂ deficiency may take years to develop because the liver stores a vast supply of this vitamin. You may develop a deficiency from certain physical conditions or from an inadequate diet. In adults, a vitamin B₁₂ deficiency usually comes from a defect in the digestive tract’s absorption of the vitamin, a condition called pernicious anemia. You may also develop a deficiency if you have had parts of your stomach or small intestine removed, which prevents the digestive tract from adequately absorbing the vitamin. In both of these cases, you need vitamin B₁₂ injections. Since plants do not contain vitamin B₁₂, strict vegetarians who do not eat eggs or milk products also need a vitamin B₁₂ supplement and can take one by mouth.

Vitamin B₁₂ deficiency can lead to anemia and to slow, progressive, irreversible damage to the nervous system. This damage will cause loss of feeling in the hands and feet, unsteadiness, loss of memory, confusion, and moodiness. To prevent these changes, people who require lifelong treatment with monthly B₁₂ injections should be reevaluated at 6- to 12-month intervals by their doctor if they are otherwise well.[1]

Unless you have one of the conditions that require B₁₂ injections, to prevent and treat a deficiency of vitamin B₁₂ you should eat more food that is rich in this vitamin rather than taking a vitamin supplement. You should take a supplement only if your diet does not provide an adequate amount.

The claims made for vitamin B₁₂ as a remedy for numerous conditions are unfounded. There is no evidence that supplements can provide more pep or counter depression or fatigue in people who do not have a deficiency.

A recent Journal of Parenteral and Enteral Nutrition (JPEN) systematic review revealed that, with a few possible exceptions, dietary supplements offer no benefits to well-nourished adults eating a Western diet and, in many cases, may be harmful. The results of this study reinforce Worst Pills, Best Pills News’s longstanding view that there is little evidence that dietary supplements are either safe or effective.

The study authors concluded that, with the possible exception of vitamin D in elderly patients and omega-3 fatty acids in patients with a history of cardiovascular disease, no data support the widespread use of dietary supplements in the U.S. and other Western countries. Indeed, the data suggest that certain commonly used dietary supplements, including beta-carotene, vitamin A and vitamin E, may be harmful. We agree.[2]

In 2023, Movement Disorders published an article which showed that taking Vitamin B₆ (pyridoxine), B₉ (folate) and B₁₂ (cobalamin) supplements for a long time and taking more than the daily recommended dose did not decrease the risk of Parkinson’s disease.[3]