B Vitamins, Homocysteine, and Health
Q. How do B vitamins lower your homocysteine level, and how important is it to have a normal level?
A. Homocysteine is an amino acid that is part of everyone’s normal body chemistry. But people with high concentrations in their blood are at increased risk for heart disease, stroke, and cognitive decline. In families with a rare genetic condition that causes very high homocysteine levels, even young children can die from heart attacks.
B vitamins — particularly B6, B12, and folic acid — lower homocysteine levels by stimulating enzymes that transform homocysteine into other, less harmful amino acids. So it seemed important to test whether lowering homocysteine levels with B vitamin supplements would, in fact, translate into health benefits.
Many doctors regard the results reported from several large studies in 2006 as disappointing, including myself. Two randomized trials that included over 9,000 patients with cardiovascular disease or risk factors for heart disease concluded that B vitamins didn’t lower the risk for adverse cardiovascular events. And another randomized trial of 276 healthy people ages 65 or over found that the group taking B vitamins had no better cognitive functioning than the group taking placebo pills.
But I don’t regard these results as the last word on the subject. The people enrolled in these studies had normal or just slightly elevated homocysteine levels. So while the results convincingly demonstrate that high doses of B vitamins don’t protect against cardiovascular disease and cognitive decline in people with basically normal levels of homocysteine, they tell us little, if anything, about the value of high-dose B vitamins for people with significantly elevated levels (defined by most testing laboratories as over 20 µmol/L). Whether such individuals should be taking B vitamins is still unknown, but I think it’s a reasonable choice.
