Antioxidant Supplements: Are They Worth It?
What's going on in the marketplace doesn't appear to be reflecting what's going on in the laboratory.
In the marketplace, Americans are now spending nearly $2 billion a year on supplements of vitamins C, E, and beta-carotene, commonly referred to as the antioxidant nutrients. Vitamin E has become the third most popular supplement after multivitamins and calcium, according to Laurie Demeritt, a spokesperson for The Hartman Group, a Bellevue, Washington–based consumer market research firm specializing in wellness products. Consumers are spending $1 billion a year on vitamin E alone, she says.
Based on preliminary results, the largest double-blind, placebo-controlled studies in history were designed and conducted, looking for a safe, natural way to prevent heart disease and cancer. Unfortunately, the results have been almost entirely negative.
For example, the HOPE study involved over 9000 people and followed them for several years. The results showed no reduction in heart attacks, strokes, or deaths from heart disease among people who took 400 International Units for an average of almost five years. Other studies enrolling a total of tens of thousands of people also failed to find benefit.
In another study, almost 20,000 women who took 50 milligrams of beta-carotene every other day were no more protected from getting cancer or heart disease than women who took a placebo, or dummy pill. The results were similar to those of Harvard's Physicians' Health Study, in which beta-carotene failed to confer any benefit for 22,000 men who had taken the substance for 12 years.
Early Research Produced Heightened Expectations
What's happening here?
The results of recent studies are "not living up to the expectations" consumers have for these nutrients, says Paul Thomas, EdD, publisher of The Daily Supplement , a newsletter in Maryland marketed primarily to healthcare professionals to guide them in their advice to patients on supplement use. Things "look less promising than they did a decade ago," he remarks. "The great bubble of hope with antioxidants, if not burst, has at least been pricked."
A decade ago, studies looking at what people eat found that those whose diets contained foods high in antioxidants were less likely to end up with chronic illnesses, including heart disease and cancer. Basic test tube research also bolstered the case for antioxidants. But, comments Regina Ziegler, PhD, a nutritional epidemiologist with the National Cancer Institute, there's this idea that because something "happens in a test tube, therefore it must be true in humans." It doesn't go that way.
"One of the reasons these [antioxidants] were oversold," she adds, was the theory that because something reduces oxidation, it decreases the risk of cancer. "I have always thought that was an overly simplistic argument," she says. "It is not at all clear that all cancers are caused by oxidative damage."
Beta-carotene Supplements: Likely Not Worth It
Certainly, beta-carotene hasn't panned out when it comes to cancer prevention. Not only have some studies shown it to be useless in the high doses given in supplements, but some research has even shown it to be harmful in certain groups of people.
A study in Finland found that male smokers who took beta-carotene for at least five years were 18% more likely than others to get lung cancer. In the United States, a study indicated that smokers, former smokers, and workers exposed to asbestos who swallowed beta-carotene supplements were almost 30% more likely than others to develop lung cancer.
There's "pretty strong evidence to throw out beta-carotene," says Eric Rimm, ScD, a Harvard nutrition researcher. Adds Jeffrey Blumberg, PhD, an antioxidant expert at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, there are "40 studies now" on beta-carotene that show "no effect, or an adverse effect," depending on the group being studied and the disease being looked at. "I would tell people, 'Don't take high doses of beta-carotene,'" meaning don't take more "than you could get in food."
In terms of beta-carotene, it is still good for you. However you can get an appropriate amount from eating orange fruits and vegetables several times a week.
Vitamin C: Easy to Get From Foods
For vitamin C, Blumberg says, "I don't think the final story is in yet." But, he adds, you don't need a supplement "if you're getting 200 to 250 milligrams in your diet." That's easy to do, he points out, as long as you consume at least five servings daily of fruits and vegetables.
His stand on vitamin C comes, in part, from research conducted by Mark Levine, MD, Chief of the Molecular and Clinical Nutrition Section of the National Institutes' of Health Digestive Diseases Branch. What Levine found, at least in healthy young men, is that with 200 milligrams of vitamin C a day, the blood becomes about 80% saturated with the nutrient, and the tissues become 100% saturated. Taking much more than 200 milligrams daily, Levine says, is "like pouring water over an already-soaked sponge."
"I think vitamin C should come from foods," he adds flatly. "We do know there is definite benefit for cancer prevention for people who eat fruits and vegetables," he says. "We don't have good evidence...that there's benefit from vitamin C by itself."
Vitamin E: The Jury Is Still Out
For vitamin E, the picture is just as bad. Multiple studies involving tens of thousands of people have failed to find benefits for cancer (except, possibly, prostate cancer), heart disease, or strokes. The evidence regarding benefits for other conditions, such as Alzheimer's disease or supporting the immune system, remains contradictory. Studies have involved both natural and synthetic forms of the alpha tocopherol form of the vitamin.
Some hope remains that one relatively untested form of vitamin E, gamma tocopherol, might produce benefits that regular vitamin E does not; however, researchers, having been disappointed by all the negative results with alpha tocopherol, are not counting their chickens too soon.
Combination of Antioxidants
Some researchers pin their hopes on combination antioxidant treatments. However, even here results have been less than impressive. The Supplémentation en Vitamines et Minéraux Antioxydants (SU.VI.MAX) study, following 13, 017 French adults for over seven years, tested a combination of vitamin C, vitamin E, beta carotene, selenium, and zinc, as compared to placebo. The results failed to show any overall reduction in cancer incidence, heart disease, or mortality. A close look at the data, however, suggests that men may have experienced some cancer risk reduction, while women did not; this type of "dredging the data," however, is questionable, and can easily lead to statistical illusions.
JoAnn Manson, MD, a Harvard researcher serving as principal investigator of the Women's Antioxidant Cardiovascular Study, which is testing vitamins C, E, and beta-carotene, isn't optimistic. "Recent trial results have been disappointing," and "I do believe that it's premature to make public health recommendations about the use of antioxidant supplements."
She adds, the antioxidant grouping "probably will not end up living up to its top billing as a miracle drug."
There is no substitution for getting these nutrients from fresh fruits and vegetables. There are other things in fruits and vegetables that provide health benefits and all these working in a synergistic way is what is shown to reduce the risk of cancer.
Lifestyle Still Important
But irrespective of future study findings, she cautions, "it's important that supplements aren't construed as taking the place of lifestyle modifications. There is a danger that people will think that simply popping a pill can replace more difficult [habit changes], and that could be detrimental. The antioxidants will never be a substitute for "basic, healthful living," she says. "It's always going to be tremendously important to quit smoking and eat a heart-healthy diet and control blood pressure and cholesterol and engage in regular exercise." Those changes, she says, "are tried and true and have been documented to be of benefit."
Public Health Agency of Canada
U.S. Food and Drug Administration Center for Drug Evaluation and Research. Available at: http://www.fda.gov/cder/.
Last reviewed February 2008 by
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