Vitamin B12 - Disease Prevention

Homocysteine and Cardiovascular Diseases

Evidence is mounting that an elevated plasma homocysteine concentration is an independent risk factor for cardiovascular diseases, such as heart disease, stroke, and peripheral vascular disease. The amount of homocysteine in the blood is regulated by at least three vitamins: folate, vitamin B₁₂, and vitamin B6.

Analysis of the results of 12 homocysteine-lowering trials showed folic acid supplementation (0.5-5 mg/day) to have the greatest lowering effect on blood homocysteine levels (25%), with vitamin B₁₂ (0.5 mg/day or 500 mcg/day) providing an additional 7% reduction.

The results of a sequential supplementation trial in 53 men and women indicated that after folic acid supplementation, vitamin B₁₂ became the major determinant of plasma homocysteine. Some evidence indicates that vitamin B₁₂ deficiency is a major cause of elevated homocysteine levels in people over the age of 60.

Two studies found blood methylmalonic acid (MMA) levels to be elevated in more than 60 % of elderly individuals with elevated homocysteine levels. An elevated MMA level in conjuction with elevated homocysteine suggests either a vitamin B₁₂ deficiency, or a combined B₁₂ and folate deficiency, in the absence of impaired kidney function. Thus, it is important to evaluate vitamin B₁₂ status as well as kidney function in older individuals with elevated homocysteine levels, prior to initiating homocysteine-lowering therapy. For more information regarding homocysteine and cardiovascular diseases, see folic acid.

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