Vitamin B12 is required for the body’s manufacture of the essential amino acid, methionine, and the associated enzyme, methionine synthase. An inadequate supply of this enzyme may lead to an excess of homocysteine. This is a naturally occurring protein in the body and has been associated with the risk of cardiovascular disease. Studies show that people with blood homocysteine levels in the top 20% of the range faced a more than doubled risk of cardiovascular disease.
Given that elevated homocysteine levels are accepted as a risk factor for cardiovascular disease, and that supplementation with the B vitamins is known to reduce homocysteine levels, it makes sense that an adequate intake of these vitamins, including B12, would be a protector against cardiovascular disease.
Science is searching for the definitive answer. But in the meantime, given the relatively small amounts of these vitamins required by the body, and the absence of any reported toxicity or adverse side effects, it is really not worth running the risk of a deficiency.
The Recommended Dietary Allowance (RDA) for vitamin B12 is only 2.4 mcg a day, an amount which should be readily obtainable, except perhaps for those following a strict vegetarian diet. A single 3 oz serving of fish or red meat may provide this quantity. Sea food may provide a lot more, and chicken, turkey, eggs, milk and cheese are also good sources.
Deficiencies in B12 are commonly found even in younger as well as older individuals and cardiovascular disease is a problem which may develop without symptoms over many years. Therefore, it would seem to be a strong argument for supplementation amongst the general population. However, check with your doctor first.