Antioxidants: Helpful or Harmful
A recent study released by the prestigious Journal of the American Medical Association (JAMA) claims that certain antioxidants can actually do more harm than good.
The massive meta-analysis looked specifically into the effects of beta-carotene, vitamin A, vitamin E, selenium and vitamin C. The results showed that the consumption of high amounts of beta-carotene, vitamin A and vitamin E in the form of supplements was correlated to a higher rate of death. The authors of the study and advocates of its findings purport that this is further evidence that taking supplements, particularly antioxidants, in high doses has no beneficial health effects and can in fact be harmful.
To truly understand the implications of this study it is important to understand some basics of the way it was conducted.
First of all, the study design is referred to as a meta-analysis. This means that the researches reviewed the outcomes of other studies and compiled the data for statistical analyses. In many cases meta-analysis can be a very valuable research tool. The problem is that the outcome of a meta-analysis study can be easily manipulated by selectively picking out studies that had the outcomes the researchers desired. In this case, the researches chose studies for the meta-analysis that showed poor outcome for people taking anti-oxidant supplements.
The next important thing to understand is why did the people in the studies taking antioxidants have an increased rate of death. The truth is that the vast majority of the research uses high doses of antioxidants to treat unhealthy people -- many of the studies look at antioxidant use by smokers or people with existing heart disease, for instance. So it is very likely that the people in the study had a higher rate of mortality not because they were taking antioxidants, but because of their predisposing risk factor for mortality from their poor lifestyle habits or pre-existing disease.
In addition to choosing studies containing people with high risk for death, the authors also omitted studies that would have changed their results. Of primary concern is the omission of two very well respected, published large studies from Italy and China that clearly showed the benefits of vitamins. Also omitted were 21 studies that when originally included in the meta-analysis showed no increase in risk or benefit from using antioxidants.
The most important thing to remember is that the majority of research shows great benefit in reducing death rate and improving health by eating a diet rich in fruits and vegetables which are loaded with anti-oxidants. Further, looking at research studies specifically evaluating the use of anti-oxidants overwhelmingly shows their safety and effectiveness to improve health. Only beta-carotene, when given in a synthetic form, has been shown to increase mortality in heavy smokers.
Understanding the limitations and bias of the study help explain the confusing outcome. In my opinion the results of this study do not warrant the questioning of the value or safety of antioxidant supplementation. However, if you are still questioning the safety of antioxidants, you can do what Mother Nature intended and trade your supplement bottles for extra helpings of fruits and vegetables.