Homocysteine is a toxic amino acid, a breakdown product of protein metabolism that has been linked to heart attacks and strokes. Several studies suggest homocysteine may contribute to atherosclerosis by damaging the inner lining of arteries and promoting blood clots.
Blood levels of homocysteine tend to be higher in people who eat a lot of animal protein and whose diets are low in fruits and leafy vegetables. These non-meat foods provide folate (a water soluble B vitamin that occurs naturally in food, equivalent to folic acid) and other B vitamins that help break down homocysteine so the body can get rid of it. We don't yet know for sure whether lowering homocysteine levels will reduce the risk of heart disease or stroke. However, there is evidence suggesting that the higher the blood levels of B vitamins, the lower the concentrations of homocysteine, and that low blood levels of folic acid are associated with a higher risk of fatal coronary heart disease and stroke.
To lower your homocysteine levels you should first reduce the amount of animal foods in your diet. Beyond that, your main strategies should be to make sure that you get plenty of vitamins B6, B12 and folate from your diet and from supplements. I recommend taking a daily multivitamin supplement that provides 400 mcg of folic acid as well as at least 50 mg of vitamin B6. It should also give you 50 mcg of B12 along with the other B vitamins. However, since B12 isn't always well absorbed through the stomach, you might consider taking it in spray form or sublingually (tablets that dissolve under the tongue).
In addition to supplements, make sure that your diet contains plenty of foods rich in folate. Breakfast cereals and foods made with enriched flour are now fortified with folic acid (since the FDA required fortification in 1996, average homocysteine levels in the United States have declined). Good natural sources of folate include spinach, asparagus, broccoli, turnip greens, citrus fruits and juices, dried peas and beans.
Andrew Weil, M.D.