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Remedies to Prevent Heart Disease Questioned B Vitamins May Not Help Those at Risk

Posted on: Tuesday, 14 March 2006, 09:01 CST

By Gina Kolata

A widely promoted B-vitamin regimen for the prevention of heart attacks and strokes has shown no beneficial effects in people at high risk, researchers are reporting in two new studies. The widely accepted hypothesis was that B vitamins folic acid, vitamin B12 and vitamin B6 could protect against homocysteine, an amino acid that some doctors said was as important and dangerous a risk factor for heart disease as cholesterol.

Studies of populations had shown that the higher the homocysteine level in the blood, the greater the risk of heart attacks and strokes.

And studies of animals had indicated that homocysteine could actually damage the tender linings of arteries, setting the stage for atherosclerosis.

B vitamins, however, reduce blood levels of homocysteine. The vitamins, which are found in a variety of foods, have no known harmful effects. And if people take the vitamins as supplements, their homocysteine levels plummet. So it seemed reasonable that taking the vitamins would be protective. It might be even better than taking statins, some said, which are well established to prevent heart disease by lowering cholesterol levels.

It is not, the new studies find.

And while some heart-disease researchers still say the vitamins help prevent heart disease, others say that remains to be seen.

"Every intervention that works in sick people also works in less sick people: Cholesterol lowering, blood pressure lowering," said Dr. Salim Yusuf of McMaster University in Hamilton, Ontario, an author of one of the new studies. "And things that don't work in sick people don't work in less sick people either."

Two of the studies will be published in The New England Journal of Medicine on April 13, and one was published in 2004 in the Journal of the American Medical Association. Together, the three studies included more than 9,000 patients and put the homocysteine hypothesis to a rigorous test: Patients at high risk of heart attack or stroke were given the vitamins, or placebos, and followed for several years.

All three studies showed that the vitamin regimens drove patients' homocysteine levels down by nearly a third; if the hypothesis were correct, patients taking the vitamins should have been better off.

Instead, they had about the same number of heart attacks and strokes as the patients taking placebos.

"The evidence is clear that this type of vitamin therapy is really not effective in reversing or benefiting advanced vascular disease," said the hypothesis' father, Dr. Kilmer McCully of the Veterans Affairs Boston Health Care System in West Roxbury, Massachusetts. McCully first proposed that homocysteine caused heart disease in 1969, and sacrificed his career to the hypothesis.

But he and others say more research is needed, adding that there might be a more complex biochemical picture than researchers had imagined. Other experts say that as far as they are concerned, the hypothesis, once so promising, is dead.

Dr. Joseph Loscalzo of Brigham and Women's Hospital in Boston, commented on the three studies in an editorial accompanying the papers in The New England Journal of Medicine: "The consistency among the results leads to the unequivocal conclusion that there is no clinical benefit of the use of folic acid and vitamin B12 (with or without vitamin B6) in patients with established vascular disease."

"One could say this dismisses the homocysteine hypothesis," Loscalzo added in a telephone interview. But he said he was not so ready to dismiss it.

He also said it was possible that B vitamins could help if people took them before heart disease had developed.

The most likely explanation for the studies' results, Yusuf of McMaster University said, was that homocysteine levels were not the cause of disease. Instead, he said, they are probably a sign of heart disease, much like fever is a sign of infection. Treating a fever with aspirin does not cure the disease, and lowering homocysteine levels with B vitamins does not cure disease either.

"We had a significant drop in homocysteine levels but practically no result," Yusuf said.

Source: International Herald Tribune

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