Study Questions Value of Antioxidant Vitamins : Health: Data on smokers suggest beta carotene raises cancer risk. Vitamin E may cut prostate cancer chances.
In a surprising study that casts doubt on the health benefits of antioxidant vitamins, a team of Finnish and American researchers has found that supplements of Vitamin E and beta carotene do not protect smokers against lung cancer--as previous studies have shown--and that beta carotene may in fact raise the risk of cancer among smokers.
The massive six-year study of 29,133 Finnish men, financed by the National Cancer Institute, also pointed to another troubling but inconclusive connection: Smokers who took beta carotene apparently had an increased risk of stroke, and a slightly increased risk of heart disease.
At the same time, the study is also the first to report another possible benefit of Vitamin E, which apparently lowered the risk of prostate cancer by 34% in men who participated in the research--a finding the lead researcher termed “very interesting and intriguing.”
Results of the long-awaited $43-million study, to be published in Thursday’s New England Journal of Medicine, come amid mounting scientific evidence that the class of vitamins known as antioxidants--which includes Vitamins C, E and beta carotene, the plant form of Vitamin A--can help prevent a broad range of illnesses, including cancer and heart disease, in smokers and nonsmokers.
A large study in China recently found substantial reductions in cancer among people who took beta carotene, Vitamin E and selenium, another antioxidant. Other smaller studies have shown a reduced risk of lung cancer in smokers who took Vitamin E and beta carotene, which prompted the NCI to join with Finnish researchers to conduct their large-scale study.
Given the previous research, the outcome of the Finnish study is extremely puzzling, even to those who conducted it.
“If you don’t have some level of confusion about how to interpret this study, you should,” Dr. Philip R. Taylor, the NCI official who supervised the research, told a group of reporters in Washington on Tuesday.
The study is likely to generate a flurry of concern among the millions of Americans who take the vitamins, either in single megadose supplements or new antioxidant formulas that manufacturers began marketing last year in an effort to capitalize on the favorable findings of previous studies.
Experts say that although the new study is too large and well-conducted to be ignored, it does not provide proof that antioxidants are harmful. Most called for additional research, and said the study should simply provide consumers with a healthy dose of skepticism toward overstated claims of the benefits of antioxidants.
Dr. Charles Hennekens, a professor of medicine at Brigham and Women’s Hospital in Boston who is conducting two other long-running studies designed to examine the benefits of antioxidants, said: “If someone has chosen to take antioxidant vitamins, I certainly wouldn’t dissuade them based on the evidence in this trial. But nor would I have told them to take them based on the evidence that we do have.”
Meanwhile, the Council for Responsible Nutrition, a trade industry group that represents 70 vitamin manufacturers, sought to cast doubt on the study, saying the participants--middle-aged men who on average had been smoking a pack a day for 36 years when the study began--had done themselves so much harm that no vitamin could counteract it.
“No one has ever suggested that the way to use these things is to adopt poor habits and carry these habits on for a lifetime and then to expect a magic bullet at the end,” said Annette Dickinson, a spokeswoman for the group.
Indeed, experts said that if there is any uniform message to the study, it is that the best protection against cancer is to quit smoking and eat a healthy diet, low in fat and high in fruits and vegetables. “The study is a reminder that smoking is not a healthy behavior,” said Dr. Demetrius Albanes of the NCI, a lead author of the study.
This study, and other research into antioxidants, sought to test the theory that the vitamins combat the effects of “free radicals,” unstable molecules in the body that damage other cells and contribute to disease. Free radicals are manufactured when a person breathes, although cigarette smoking and pollution are known to increase their production.
The process is one of oxidation; in much the same way as lettuce turns rancid, the body’s tissues turn rancid with exposure to free radicals. Antioxidants, some scientists believe, help stop this process.
To conduct their study, Albanes and his colleagues separated the participants into four groups of about 7,250 men apiece. One group took both beta carotene and Vitamin E; another took only beta carotene; another took just Vitamin E, and the fourth group received placebos.
During the study, 876 of the men developed lung cancer. Taking Vitamin E appeared to have no significant effect; 433 of the cancer patients took the vitamin and 443 did not.
But among those taking beta carotene, the researchers observed a statistically significant difference; 474 of the lung cancer patients took this supplement, while 402 did not. That translates into an 18% increase in lung cancer rates for those who took beta carotene.
The study’s authors and other experts could not explain the unexpected findings with respect to beta carotene--which has always been considered safe--except to say that it is possible those results were due to chance.
“It could have been a fluke,” said Dr. Jeffrey Blumberg, who runs a government-financed antioxidants research laboratory at Tufts University.
But Blumberg and others offered several explanations for the Vitamin E outcome. One theory is that the vitamin did not help because the dose was too low--only 50 milligrams (roughly 50 international units) per day, whereas other studies have shown benefits accrue at 400 international units or more. Another is that the study did not last long enough to document a favorable effect.
As to the findings on strokes, heart disease and prostate cancer, Albanes said those need to be explored further. The study found that men who were taking beta carotene had 13% more deaths from heart disease and stroke--a finding that Albanes said is not significant enough to warrant a conclusion about the effects of the supplement on those diseases.
Times staff writer Ray Delgado in Washington contributed to this article.
