Healthy Skepticism Library item: 3861

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Publication type: news

Kolata G.
Studies Find B Vitamins Don't Prevent Heart Attacks
New York Times 2006 Mar 12
http://www.nytimes.com/2006/03/12/health/12cnd-heart.html?ex=1142830800&en=3372356f1677c61e&ei=5070&emc=eta1

Notes:

Ralph Faggotter’s Commments:

We have known about a link between elevated homocysteine levels and heart disease risk for a long time, and it was hoped that lowering the homocysteine level ( with B group vitamins) would lead to a lessening of this risk.

Sadly, this turns out not to be the case.
Homocysteine is probably a flag of, rather than a cause of, heart disease.

The lesson here is, don’t jump to therapeutic conclusions based soley on theoretical possibilities.
Do the trials first!

Full text:

Studies Find B Vitamins Don’t Prevent Heart Attacks

By GINA KOLATA
Published: March 12, 2006

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 today.

The hypothesis was that B vitamins – folic acid, vitamin B12 and vitamin B6 – can protect people 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 showed that the higher the homocysteine level in the blood, the greater the risk of heart attacks and strokes. And studies of animals indicated that homocysteine can actually damage 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, including fruits and vegetables, have no known harmful effects. And if people take them as supplements, their homocysteine levels plummet. About 35 percent of Americans take B vitamins, mostly in the form of multivitamin pills, according to the Council on Responsible Nutrition, a trade group.

So it seemed reasonable to many doctors and patients to expect 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 was not, the new studies find.

And while some say it still is possible that the vitamins help healthy people prevent heart disease, others say that remains to be seen.

“Every intervention that works in sick people also works in less sick people,” said Dr. Salim Yusuf of McMaster University in Ontario, Canada, an author of one of the new studies. “Cholesterol lowering, blood pressure lowering. 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. (The New England Journal papers were being discussed today at a meeting of the American College of Cardiology and so The Journal lifted its embargo on them.) Together, the three studies included more than 9,000 patients and they put the homocysteine hypothesis to science’s most rigorous test: Patients at high risk of a heart attack or stroke were given the vitamins or placebos and followed for years.

All three studies had the same result – the vitamins drove patients’ homocysteine levels down so much, nearly a third, that if the hypothesis were correct, patients taking them 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’s father, Dr. Kilmer McCully of the V.A. Boston Health Care System in West Roxbury. Dr. McCully first proposed that homocysteine caused heart disease in 1969 and literally sacrificed his career to the hypothesis.

But he and others say that more research is needed, adding that there might be a more complex biochemical picture than researchers had imagined.

Others say that as far as they are concerned, the hypothesis, once so promising, is dead.

One of the New England Journal of Medicine papers, sponsored by the Canadian Institutes of Health Research, involved 5,522 patients aged 55 or older who had diabetes, or who had had a heart attack or who had documented heart disease. They were randomly assigned to take 2.5 milligrams a day of folic acid, 50 milligrams of vitamin B6 and 1 milligram of vitamin B12 or to take a placebo and were followed for five years.

The other study, the Norwegian Vitamin Trial, involved 3,749 men and women aged 30 to 85 who had recently had a heart attack. They were randomly assigned to take one of four regimens: vitamin B12 and B6; folic acid and vitamin B6; vitamin B6; or placebo. The study lasted for three years and four months.

The third study, published last year in the Journal of the American Medical Association, involved 3,680 stroke patients randomized to take the vitamins or not.

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,” Dr. Loscalzo said in a telephone interview. But he is not so ready to let it go, citing, “abundant evidence that argues that homocysteine has an adverse effect on blood vessels and should contribute to atherosclerosis.”

And so, Dr. Loscalzo says, “if you believe those observations, you have to think of an alternative explanation.” He suggests it may involve chemical reactions in the blood vessels whereby B vitamins themselves cause cells to divide and plaque to grow. Homocysteine may be a culprit, but doses of B vitamins that exceed the recommended daily amounts that can be obtained from foods may have deleterious effects that cancel out their good effect of homocysteine lowering.

He also thought it was possible that B vitamins might be helpful if people took them earlier, before heart disease had a chance to develop.

Others are ready to move on.

“We were surprised but as scientists we accept the finding,” Dr. Kaare Bonaa said in a telephone interview. Dr. Bonaa, the lead author of the Norwegian study and a professor of medicine at the University of Tromso in Tromso, Norway.

“The whole homocysteine story should be rethought,” says Dr. Yusuf.

The most likely explanation for the studies’ results, he says, is that homocysteine levels never were causing disease. Instead, he says, they are a sign of heart disease, just like fever is a sign of an infection. Treating a fever with aspirin does not cure the disease and lowering homocysteine levels with B vitamins does not cure disease either, he says.

“We had a significant drop in homocysteine levels but practically no result,” Dr. Yusuf said. “Pretty compelling, isn’t it?”