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Another nutrition myth went down the drain this week. It seems that antioxidant vitamins don’t quite live up to their hype.
Researchers reviewing 68 studies on the effect of antioxidants on life span reported in the Journal of the American Medical Association this week that consumption of beta carotene, vitamin A, vitamin C, vitamin E and selenium, whether singly or combined, did not reduce the risk of premature death.
If anything, the researchers concluded, there was actually a slight increase in risk of premature death among antioxidant supplement takers (with the exception of vitamin C and selenium).
Antioxidants have been hypothesized to reduce the oxidative damage to the body caused by so-called “free radicals.” Some have suggested that antioxidant supplements may reduce the risk of cancer and heart disease. Such claims helped fuel the growth of the multi-billion dollar nutritional supplement industry.
The researchers didn’t conduct new experimental research. Instead, they conducted a systematic review of the results of 68 studies involving 232,606 antioxidant supplement users, combing their results using a controversial statistical technique known as “meta-analysis.”
The conclusion that antioxidant supplements don’t appear to help you live longer is likely on a sound footing. Even without statistically combining the studies through meta-analysis, it’s fairly clear that antioxidant supplements are ineffective for increasing longevity.
Of the 68 studies examined, 66 studies reported no statistically significant association between supplement use and longevity. The remaining two studies actually reported statistically weak increases in premature death with supplement use.
One strength of this analysis is that longevity is perhaps the most objective measure of health. A potential weakness of the study – at least in terms of putting the myth to bed – is that the researchers didn’t examine whether supplement use reduced the risk of cancer or heart disease – two diseases often touted as preventable by antioxidant use. This shortcoming may enable the supplement industry to keep making unproven claims about antioxidants preventing those two diseases.
The study’s other conclusion concerning the risk of antioxidant supplements increasing the risk of premature death rests on shaky ground, however.
The researchers reported that beta-carotene supplements taken singly, vitamin A supplements taken singly or in combination with other antioxidant supplements; and vitamin E supplements taken singly or in combination with other antioxidant supplements were associated with 6 percent, 16 percent and 4 percent, respectively, increases in risk of premature death among the study group.
Although the three reported increases in risk were statistically significant, this is not likely a reason to fret about supplement use.
All three results are relatively weak statistical correlations that would require large, well-designed, and carefully controlled clinical trials to confirm. But since there’s no apparent health benefit from taking these supplements to begin with, there’s probably little reason to take them or to study them further.
It will be interesting to see what impact this study has on the nutritional supplement industry. A Google search on “antioxidant” produced advertisements proclaiming, “Natural Antioxidant = Better Health”; and “Naturally Remove Free Radicals.”
A search on “beta-carotene” produced, “Reduce Cancer and Disease.”
A “vitamin E” search produced “Feel Strong. Be Healthy” and “You can look and feel 20 years younger than you actually are.”
Then there’s the vitamin C industry that’s been built around double-Nobel Laureate Linus Pauling, perhaps the most prominent promoter of the notion that mega-doses of vitamin C improve health.
In his highly publicized 1970 book “Vitamin C and the Common Cold,” Pauling claimed that taking 10 times the recommended daily allowance of vitamin C reduced the incidence of colds by 45 percent. In his 1986 book, “How to Feel Better and Live Longer,” Pauling claimed that mega-doses of vitamins “can improve your general health … increase your enjoyment of life and can help in controlling heart disease, cancer, and other diseases and in slowing down the process of aging.”
As Quackwatch.org's Dr. Stephen Barrett points out, “Although Pauling's mega-vitamin claims lacked the evidence needed for acceptance by the scientific community, they have been accepted by large numbers of people who lack the scientific expertise to evaluate them. Thanks largely to Pauling’s prestige, annual vitamin C sales in the United States have been in the hundreds of millions of dollars for many years.”
While the jury is probably still out on whether typical use of antioxidant supplements pose any sort of long-term health risk, it is possible to overdose on antioxidants, particularly vitamin A. With respect to Pauling and mega-doses of vitamin C, Dr. Barrett says, “The physical damage to people he led astray cannot be measured.”
None of this is to say that no nutritional supplement can have any value under any circumstances. But before falling blindly for claims made by the nutritional supplement industry, you should probably do your own research and check with your physician.