(HealthDay is the new name for HealthScoutNews.)
MONDAY, June 30, 2003 (HealthDayNews) -- Earlier this month, researchers reported they couldn't find enough evidence to support claims that vitamin supplements reduce the risk of heart disease.
Now comes a new study from a panel of prevention experts who say they can't recommend supplements to ward off heart disease or cancer.
The quasi-governmental group, called the U.S. Preventive Services Task Force, found insufficient evidence to either promote or discourage taking supplements to prevent cancer and cardiovascular ailments such as strokes and heart attacks. The fence-sitting covers antioxidants such as vitamins A, E and C alone or in combination with each other; multivitamins; and multivitamins that contain the nutrient folic acid.
But the absence of good data doesn't necessarily mean the benefits of supplements are there for the discovery. In one case, solid evidence led the panel to caution against taking extra beta carotene, which the body converts into vitamin A, for cancer or heart disease. Not only do the supplements fail to protect against these illnesses, but they appear to do more harm than good in smokers by raising the risk of lung cancer and premature death.
"With the exception of vitamins for which there is compelling evidence of net harm (e.g., beta-carotene supplementation in smokers)," the report says, "there is little reason to discourage people from taking vitamin supplements. Patients should be reminded that taking vitamins does not replace the need to eat a healthy diet."
The panel, which reviewed 38 published studies, also cautioned consumers from loading up on megadoses of vitamins in the hopes that if a little is good a lot is better. "Some vitamins, such as A and D, may be harmful in higher doses; therefore, doses greatly exceeding the recommended dietary allowance (RDA) or adequate intake (AI) should be taken with care while considering whether potential harms outweigh potential benefits," the report says.
The prevention task force is a group of private health experts convened by the government's Agency for Healthcare Research and Quality. The new report appears in the June 30 issue of the Annals of Internal Medicine. It marks the first time the group has looked at the issue of supplements.
Janet Allan, vice chairwoman of the panel and dean of the school of nursing at the University of Maryland, says the report's conclusions don't rule out the possibility that supplements lower the risk of cancer and heart and vessel diseases. That just hasn't been proved yet.
"The research is young in this area," says Allan, who notes the studies she and her colleagues reviewed were typically short. Longer studies might better tease out the benefits of diet aids if they exist.
Researchers are now conducting at least eight prevention trials of vitamin supplements and cardiovascular disease, and four prevention trials of the nutrients and cancer, she says: "In the next decade, we'll have a lot better evidence to look at."
John Hathcock, vice president for nutritional and regulatory science at the Council for Responsible Nutrition, a Washington, D.C.-based supplement industry group, says the latest report provides no new information. "It doesn't tell us anything different from what we already know."
Still, Hathcock says his group doesn't dispute the thrust of the report, that dietary supplements haven't been proven to reduce the risk of cancer or cardiovascular disease. If such an effect does exist, he adds, it's likely to be rather small.
However, Hathcock says evidence supports taking supplements to guard against specific tumors -- vitamin C and stomach cancer, for example, and vitamin E for prostate and colon tumors.