High blood levels of the amino acid homocysteine may raise the risk of heart disease, stroke and blood clots in the legs, a new study confirms. The good news, researchers say, is that supplements containing the B vitamin folic acid might help reduce this risk.
Homocysteine is a normal byproduct of metabolism, but high levels of the amino acid in the blood have been linked to heart disease, stroke and blood clots. Folic acid is known to aid in breaking down homocysteine, and researchers are studying whether the vitamin can help ward off cardiovascular disease by lowering homocysteine in the blood.

But while this question is not yet answered, existing research gives "strong evidence" that high homocysteine levels do promote cardiovascular disease, according to the new report, published in the November 23rd issue of the British Medical Journal.

The researchers, led by Dr. David S. Wald of Southampton General Hospital in the UK, base that conclusion on their review of 92 studies on homocysteine and cardiovascular disease risk.

Across the studies, they report, each unit increase in blood homocysteine was associated with a 32% to 42% increase in the risk of ischemic heart disease, in which blood flow to the heart is reduced. Similar patterns were found for stroke and deep vein thrombosis (DVT)--blood clots in deep veins, usually in the legs, that can be life-threatening if they dislodge and travel to the lungs.

On the bright side, though, Wald's team estimates that lowering homocysteine levels by an amount achievable with daily folic acid supplements could cut the risks of heart disease, stroke and DVT.

To "maximally" cut homocysteine levels--and, potentially, disease risk--a person would have to take about 0.8 milligrams (mg) of folic acid a day, according to Wald's team. US dietary recommendations call for adults to get 0.4 mg of folic acid daily.

In the US, where many grains are fortified with folic acid, Wald told Reuters Health, a healthy diet plus a daily multivitamin containing folic acid may help maintain normal homocysteine levels.

"Adults," Wald said, "particularly those aged 55 and older, stand to benefit from taking a folic acid supplement everyday."

Currently, the American Heart Association does not recommend taking folic acid specifically for the prevention of cardiovascular disease, due to the lack of studies showing the vitamin prevents these conditions. However, it does advise that people at risk of cardiovascular disease be especially sure to get enough folic acid, as well as vitamins B-6 and B-12, in their diets.

Besides fortified grains, good dietary sources of folate--the form of the vitamin that naturally occurs in food--include beans, leafy green vegetables and orange juice.