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Victims of the rare genetic disorder known as homocystinuria usually die by age 20 from heart attack or stroke. They also have high blood levels of the amino acid homocysteine, a by-product of protein metabolism. That's highly suggestive of a cause-and-effect relationship, but after decades of investigation, the link between homocysteine and heart disease is still elusive. Says Dr. Andrew Bostom, co-director of the Cardiac Rehabilitative program at Memorial Hospital in Pawtucket, R.I.: "We have tantalizing suggestions that we might actually be dealing with a real risk factor, but we don't have smoking-gun evidence."
They do, however, have a plausible explanation for how homocysteine possibly works. If too much circulates in the blood, researchers believe, it may combine with LDL to form large molecules that are especially likely to attract the immune-system cells that help form plaques.
The good thing about homocysteine is that if it does prove to be a significant cause of heart disease, the treatment is in hand: studies have consistently shown that homocysteine can be easily controlled with B vitamins and folic acid, either in the diet or in supplements. The most recent study appeared two months ago in the New England Journal of Medicine: a government requirement that all flour, pasta and other grain products manufactured after Jan. 1, 1998, be enriched with folic acid (to stave off spinal-cord defects in newborns) has already measurably reduced homocysteine levels across the board.
New risk factors identified, old risks reassessed, varying degrees of uncertainty about every medical study ever published--it all seems so confusing, you may be tempted just to throw a steak on the grill, butter your baked potato and forget the whole thing.
But that would reflect a misunderstanding about how science works. It is not a steady march from ignorance to knowledge. It's more like a mountaineering expedition. On the way up an unscaled peak, climbers will gain some altitude on one route, then find it's a dead end. They'll spot a better one, backtrack a little and move on. The fact that they sometimes have to take a step backward for every two steps forward doesn't mean they're wasting their time. It means that inching up an uncharted mountain is tough work.
When you step back, though, and take a look at the overall picture--a long view from the upper slopes of the mountain--it turns out in hindsight that the path was clear. So it is with medical science. From the perspective of 1999, the past 40 years' worth of research points to a consistent theme: eat a balanced diet that includes lots of fruits and vegetables and fewer animal-based foods; don't smoke; and get as much exercise as you can comfortably maintain.
If it sounds as though nothing much has changed in the past three decades, that's because the basics of cardiac health--the base of the mountain--have been there all along. What has changed is doctors' understanding of why it's all true. And they're continuing to refine their knowledge so that the confusing new research emerging from the labs will one day stand on an equally firm footing. Until that happens, the best bet is to focus on those basics. Your heart will thank you for it.
--Reported by Christine Gorman and Alice Park/New York