Harvard Heart Letter

Ask the doctor: Should I worry about my homocysteine level?

Q. What's the current status of homocysteine as a risk factor for heart disease?

A. Homocysteine is a byproduct of digestion found in everyone's blood. "Normal" levels of homocysteine range from 5 to 15 micromoles per liter (?mol/L). People with levels of 50 or higher are at increased risk of cardiovascular events. A very few families have genetic defects that raise their levels to well over 100. In these families, even children younger than 10 can develop atherosclerosis and die of a heart attack or stroke.

Higher dietary intake of B vitamins lowers homocysteine levels, and many foods sold in the United States have been supplemented with B vitamins since the 1980s. In 2006, two large placebo-controlled studies reaffirmed that B vitamins, especially folate, lowered homocysteine levels, but they found no evidence that doing this translated into a reduced risk of heart disease. In addition, a recent analysis of unpublished data about a gene that affects homocysteine levels showed that lifelong moderate elevations in homocysteine have little or no effect on heart disease.

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