Two Studies Deflate Benefits of B Vitamins
Monday, March 13, 2006
Contrary to a widely promoted theory, B vitamins do not cut the risk for heart attacks or strokes, according to two large new studies.
The findings, released yesterday, are the latest in a series of recent studies that have found vitamins and other dietary supplements fail to have the health benefits they are touted for.
The new findings undermine a theory that taking B vitamins to reduce levels of an amino acid in the blood called homocysteine could protect against heart attacks and strokes. Previous research had indicated people with high homocysteine levels were at greater risk.
Although the new studies did show that the vitamins cut homocysteine levels, that did not translate into a reduction in the risk for heart attacks or strokes.
In the first study, Eva Lonn of McMaster University in Canada and her colleagues gave 5,522 Americans and Canadians who had heart disease or diabetes either the supplements or a placebo for five years. Although homocysteine levels among those taking the supplements fell, they were no less likely to die from a heart attack or stroke, the researchers found.
In the second study, Kaare Harald Bonaa of the University of Tromso in Norway and colleagues researchers gave 3,749 patients who had had a heart attack within the previous week the vitamins or a placebo for more than three years on average. Again, while those receiving the supplements had lower homocysteine levels, they were no less likely to have another heart attack or a stroke, or to die from heart disease.
The studies, released early by the New England Journal of Medicine to coincide with their presentation at an American College of Cardiology meeting in Atlanta, confirm the results of another large study that was published in 2004 in the Journal of the American Medical Association.
"The consistency among the results lead to the unequivocal conclusion that there is no clinical benefit of the use of folic acid and vitamin B12 (with or without the addition of vitamin B6) in patients" with heart disease, wrote Joseph Loscalzo of the Brigham and Women's Hospital in Boston in an editorial that will be published with the studies.
The Council for Responsible Nutrition, a trade group representing dietary supplement makers, said the findings did not rule out the possibility that the vitamins may reduce the risk for heart disease among healthy people.
"These studies did not test whether B vitamins used by healthy people can help keep them healthy. Instead, they looked at whether B vitamins can treat or reverse heart disease in people who already have it. Vitamins should not be expected to perform like drugs -- their greatest promise is in prevention," said Annette Dickinson in a written statement.
Kilmer McCully of the V.A. Boston Healthcare System in West Roxbury, who proposed the homocysteine theory, agreed, adding that more research is needed to understand the exact role of the amino acid in heart disease.
"You really can't deny that homocysteine is involved in the disease process," McCully said in a telephone interview. "There are hundreds, if not thousands, of papers showing that."
But Steven E. Nissen, president of the American College of Cardiology, said the findings should end debate about the theory, which had already lost credibility among many scientists. "The homocysteine theory really isn't getting much attention anymore," he said.
The findings follow a number of disappointing studies testing vitamins and other dietary supplements for health reasons. Recent studies have failed to find a clear benefit for glucosamine and chondroitin for arthritis, saw palmetto for prostate problems and echinacea for the common cold.
Another study presented at the cardiology meeting did surprise researchers when it did not find any benefit to combining the blood-thinner Plavix with aspirin for preventing heart attacks, strokes or deaths in heart patients. Earlier research had indicated that the combination would be effective. The new study, involving more than 15,000 high-risk patients, did not find any overall benefit and even suggested the combination may be dangerous for some patients.