The Hidden Heart Disease Risk Factor

As the search for predictors and preventions of heart disease continues, homocysteine (a building block of protein) has emerged as the latest risk factor for coronary artery disease. While not as potent a risk factor for heart disease as cholesterol, homocysteine may be running a close second.

Like cholesterol, a high concentration of homocysteine in the blood can damage artery walls and contribute to blocking off blood vessels. Its potential artery-damaging effects have been suggested for at least thirty years. But only lately has the substance moved, and rather swiftly, to center stage as a risk factor for heart disease.

Homocysteine is an amino acid (one of the chemical compounds that forms proteins). Everyone produces it, mainly from eating animal products. Normally, the substance is converted into other non-damaging amino acids. But in some people, this conversion is sluggish and results in the accumulation of homocysteine in the blood. In the past decade, there's been an explosion of research showing a relationship between high levels of homocysteine in the blood and cardiovascular disease.

Research has also shown that homocysteine levels can be lowered through dietary changes and supplements that increase the intake of B6 and B12 vitamins and folic acid. What hasn't yet been proven is whether or not lowering the levels of homocysteine has a preventive benefit, but such research is underway. Studies indicate that this problem is strongly influenced by diet -- specifically, low blood levels of vitamins B-6, B-12 and folic acid in particular. These vitamins convert homocysteine into other harmless amino acids. So, it's being suggested by some health professionals and supplement manufacturers that consuming more of these vitamins may, at least in part, decrease homocystine concentrations and cardiovascular disease risk.

But not so fast, says the American Heart Association (AHA). The AHA points out that everything we know so far about homocysteine, vitamins and heart disease comes from epidemiological studies (where groups of people, as opposed to individuals, are investigated). What has not been done are clinical trials, where some individuals receive the vitamins and others do not. Under these procedures, the vitamins' effects could not be attributed to dietary variations, age, health status or other factors. In addition, optimal amounts (which are currently unknown) could be determined, and toxicity would be monitored.

What to do?

Until clinical trials are conducted, be cautious about taking high doses of "B" vitamins. Too much folic acid can mask vitamin B12 deficiency, and extremely high doses of B6 can cause nerve damage. The AHA recommends that we obtain an adequate intake of these vitamins by eating a variety of foods, rather than supplements. Good sources of folic acid are citrus fruits, tomatoes, vegetables and grain products. Also, beginning in January 1998, grain and cereal products will be fortified with folic acid. The richest sources of B6 are chicken, fish, liver, pork, kidney and eggs, as well as unmilled rice, soybeans, oats, and whole-wheat products. The richest sources of B12 are animal products, peanuts and walnuts.

Still, if you don't eat a well-balanced diet, or you feel the need for a little "extra protection," there is no harm in taking daily multivitamins. Current information indicates that an optimal daily intake is 3 to 3.5 milligrams of B6, 350 to 400 micrograms of folic acid, and 5 to 15 micrograms of B12 -- amounts that are contained in many multivitamins. If you are at high risk for heart disease, you may want to discuss all this with your doctor.