Rethinking a Heart-Disease Risk

By MICHAEL D. LEMONICK

If you follow medical news even casually, you have probably heard about homocysteine. Over the past few years, this amino acid, produced in the body, has been implicated as an important risk factor for cardiovascular disease--maybe even more important than LDL, or "bad cholesterol." According to many studies, elevated homocysteine levels can triple the chance that you'll get heart disease and significantly increase your risk of stroke--and maybe of Alzheimer's disease as well. Researchers even have a plausible explanation: homocysteine seems to damage the internal walls of the arteries--a major source of cardiovascular problems.

But other studies have failed to find any increase in risk at all. Now comes a report in last week's Journal of the American Medical Association that may go a long way toward reconciling this paradox. By doing a meta-analysis (a combined statistical analysis of many previous studies), a team led by Dr. Robert Clarke of Radcliffe Infirmary in Oxford, England, has deduced that homocysteine is a risk factor--but not a huge one, at least for most healthy people. The latest results say that reducing homocysteine levels in the blood 25% lessens the risk of heart disease 10% and the risk of stroke 19%--not bad, but not fabulous either.

Yet there are cases in which homocysteine levels may prove vitally important. People with kidney disease or diabetes, for example, or those who have a family history of heart disease are much more likely to suffer a heart attack. For them, even a modest decrease in cardiac risk can pay big dividends. Moreover, some people have a genetic mutation that reduces levels of a homocysteine-eating enzyme. A second meta-analysis, out of the Netherlands and also reported in last week's JAMA, shows that the mutation raises heart-disease rates 16%--and thus makes the impact of homocysteine reduction correspondingly greater.

Fortunately, there's a simple way to minimize that effect: boost your intake of B vitamins, especially folic acid. You don't even have to take vitamin supplements. In 1998 the government mandated that cereal and flour manufacturers add folic acid to their products --not to fight heart disease but because it prevents neural-tube defects such as spina bifida in newborns. The other major sources of B vitamins are beans and--you guessed it--leafy green vegetables.

The bottom line, says Dr. Peter Wilson, of the Boston University School of Medicine, who wrote an editorial accompanying the two JAMA articles: "If you're already at high risk for heart disease, having your homocysteine levels tested is probably appropriate. If you're in good health, there's no point." Taking a multivitamin with 400 micrograms of folic acid certainly won't hurt. An even better idea, as always, is to eat plenty of leafy green vegetables, since they're high in the sorts of natural compounds that not only protect your heart but also may reduce your cancer risk.

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