Folic acid, the B vitamin that protects against birth defects, also may reduce heart disease risk, according to a meta-analysis study published in the British Medical Journal (2006, vol. 333, no. 7578).

Folic acid, or folate, helps lower blood levels of the amino acid homocysteine. Elevated plasma levels of homocysteine may damage coronary arteries and increase the risk of blood clots; several studies have linked high homocysteine levels to an increased risk for heart disease and stroke.

Taking 800 mcg of folic acid daily decreases homocysteine levels and appears to lower the risk of heart attack by 15 percent and stroke by 24 percent, say researchers at London's Wolfson Institute of Preventive Medicine who analyzed the results of several published studies.

The RDA for folic acid is 400 mcg per day for (nonpregnant) adults, only half of what is needed to lower homocysteine levels significantly and reduce heart disease and stroke risk.

Several studies have shown that the body absorbs 100 percent of supplemental folic acid, while it absorbs only 50 percent of the folic acid that naturally occurs in foods. For optimal health, enjoy folate-rich foods—such as green leafy vegetables, beans, lentils, sunflower seeds, citrus fruits, avocados, and fortified grains—and back these up with a good multivitamin, or additional supplement.