Are antioxidant supplements safe?
Many people take antioxidant supplements – particularly beta carotene, vitamins A and E, vitamin C, and selenium – because they think that they’re good for them. But are they? You may have heard reports that a new study brings these supplements into question.
Antioxidants and health
Studies have shown that people whose diets are rich in fruits and vegetables have lower cancer rates. This has lead to the theory that these diets contain substances which protect against the development of cancer, and antioxidants have been pinpointed as a possible source. There is definitely intense interest and scientific investigation into this topic. So far, however, no large, well designed studies have shown that dietary supplementation with extra antioxidants reduces the risk of developing cancer.
Antioxidants are also thought to have a role in slowing the aging process and preventing heart disease and strokes. Unfortunately, again, the data is inconclusive that it is antioxidants specifically that have this effect.
New study questions findings
Enter the new study that states the supplements may, in fact, have some impact on health – but a negative one. In a press release from the Journal of the American Medical Association (JAMA), researchers from the Copenhagen University Hospital stated that they have found that the supplements may actually be associated with an increased risk of death.
Goran Bjelakovic, M.D., Dr.Med.Sci., of the Center for Clinical Intervention Research, Copenhagen University Hospital, Copenhagen, Denmark, and colleagues conducted an analysis of previous studies to examine the role of antioxidant supplements on the death of adults in studies of the preventative effects of the supplements.
Using electronic databases and bibliographies, the researchers looked at 68 randomized trials representing 232,606 participants. The authors also classified the trials according to the risk of bias based on the quality of the methods used in the study, grouping them into two groups – “low-bias risk” (high quality) or “high-bias risk” (low quality).
When the researchers looked at all the studies, regardless of how they evaluated the quality of the studies’ research, they found no significant association between antioxidant use and mortality. But when they separated out the studies that they considered to be of higher quality (47 trials involving 180,938 participants), the antioxidant supplements were associated with a 5 per cent increased risk of mortality.
Specifically, use of beta carotene, vitamin A, and vitamin E was associated with 7 per cent, 16 per cent and 4 per cent, respectively, increased risk of mortality, whereas there was no increased mortality risk associated with vitamin C or selenium use.
“Our systematic review contains a number of findings. Beta carotene, vitamin A, and vitamin E given singly or combined with other antioxidant supplements significantly increase mortality. There is no evidence that vitamin C may increase longevity. We lack evidence to refute a potential negative effect of vitamin C on survival. Selenium tended to reduce mortality, but we need more research on this question,” the authors write.
“Considering that 10 per cent to 20 per cent of the adult population (80-160 million people) in North America and Europe may consume the assessed supplements, the public health consequences may be substantial. We are exposed to intense marketing with a contrary statement, which is also reflected by the high number of publications per included randomized trial found in the present review.”
Recent study brought into question
However, other researchers have called the review study into question. Science Daily quoted Balz Frei, professor and director of the Linus Pauling Institute at Oregon State University, one of the world’s leading institutes that studies these topics, as saying “This is a flawed analysis of flawed data, and it does little to help us understand the real health effects of antioxidants, whether beneficial or otherwise.”
And an Associated Press article quoted Meir Stampfer, professor of nutrition and epidemiology at the Harvard School of Public Health, as saying almost the same, stating “This study does not advance our understanding, and could easily lead to misinterpretation of the data.”
Critics also argue that the study may have found increased mortality because the larger studies included patients who had been diagnosed with terminal conditions. Another possibility is that some individuals who supplement then make poor nutritional choices because they believe they are protected.
To supplement or not to supplement
One thing seems clear: the original finding that eating more fruits and vegetables can help prevent cancer, heart disease, and stroke has not been called into question. So be sure to get your 5-10 servings per day of these antioxidant rich foods. If you decide to take supplements, chose carefully and don’t go over recommended daily limits. And stay tuned for more studies on the topic.