Vitamin E and beta-carotene pills are useless for warding off major heart problems, and beta-carotene, a source of vitamin A, may be harmful, an analysis of key studies has concluded.
Many experts say the finding, published this week in The Lancet medical journal, settles the issue of antioxidant vitamins for heart health.
But others argue that the pills might still prove useful if started earlier and that while they do not seem to prevent heart attacks and premature death, further studies may show they help to delay the onset or progression of heart disease or other blood vessel problems.
Antioxidant nutrients, especially vitamin E, were widely recommended a few years ago as a way of keeping the heart healthy. However, several recent large studies failed to show any benefit, and a few raised the possibility that the pills might be harmful for some.
The latest research, conducted by scientists at the Cleveland Clinic Foundation, analyzed the pooled results from 15 key studies involving nearly 220,000 people.
"The public health viewpoint would have to be that there's really nothing to support widespread use of these vitamins," said Dr. Ian Graham, a professor of cardiology at Trinity College in Dublin, Ireland.
Most of the participants in the studies either already had heart or blood vessel disease or were at increased risk of such problems. Seven of the studies involved vitamin E alone or in combination with other antioxidants. Eight involved beta carotene alone or with other antioxidants. The follow-up period ranged from one to 12 years.
The researchers found that vitamin E did not reduce death from cardiovascular or any other cause and did not lower the incidence of strokes.
Beta carotene was linked with a 0.3 percent increase in the risk cardiovascular death and a 0.4 percent increase in the risk of death from any cause by the end of the study.
"For heart health, we've answered the question and one is potentially hazardous," said one of the investigators, Dr. Mark Penn, a Cleveland Clinic cardiologist.
Alice Lichenstein, nutrition spokeswoman for the American Heart Association, agreed.
"I think there are enough studies that have looked at a diverse enough group of individuals that it's unlikely that we're going to have a flip-flop," said Lichenstein, a professor of nutrition science and policy at Tufts University who was not connected with the research.
The idea that antioxidant vitamins might ward off heart trouble was plausible. Test tube studies indicated that antioxidants protect the heart's arteries by blocking the damaging effects of oxygen. The approach works in animals, and studies show that healthy people who eat vitamin-rich food seem to have less heart disease.
However, experts say that perhaps antioxidants work when they are in food, but not when in pills. Some even think antioxidants may have been a red herring and that maybe people who eat vitamin-rich food generally take better care of themselves and that's why they have lower heart disease risks.
However, Jeffrey Blumberg, a professor of nutrition and chief of the Tufts antioxidants research lab, maintained that scientists should not write off antioxidants for heart health just yet.
"If in a six-year study, the same number in the vitamin E group and the control group died, but the ones in the vitamin E group died a little later in that six-year period, that is something that needs to be looked at," Blumberg said.
"Some of the studies showed benefits in other areas, such as ... cardiac arrythmias, which suggested there were some benefits in some subsets of groups," he said.
John Hathcock, vice president of scientific and international affairs at the Council for Responsible Nutrition, a trade group for makers of antioxidants and other dietary supplements, noted that although animal studies and observations in humans suggested the pills would best be used in healthy people, the key studies were done in people who were already either sick or at elevated risk of heart disease.
"Ultimately, the end points of deaths and heart attacks are valid, but if you start when the person is already at high risk or has disease, then it may be too late for the benefit to occur," Hathcock said.