Readers of this blog are likely to take the value of antioxidants for granted. And indeed, a part of my overall anti-aging regimen is the firewall against oxidative damage which includes a number of antioxidants. Research studies supporting the value of antioxidants are frequently cited both in this blog and in my longevity treatise. However, serious research publications also appear from time to time that question the value or even the safety of antioxidant consumption. I cite and comment on two of these here.
One such study, published in 2007 in the Journal of the American Medical Association (JAMA), is entitled Mortality in Randomized Trials of Antioxidant Supplements for Primary and Secondary Prevention. The study was a meta-analysis based on synthesizing data from other studies. “We included 68 randomized trials with 232 606 participants (385 publications).” The data for the entire sample of trials reported showed that there was no significant impact of taking antioxidant supplements on mortality, one way or the other. However, when the trials were separated into two categories “high-bias risk trials” and “low-bias risk trials,” the data for the low-bias trials showed a significant association between taking antioxidants with increased mortality – the opposite of the hoped-for result. “Multivariate meta-regression analyses showed that low-bias risk trials (RR, 1.16; 95% CI, 1.05-1.29) and selenium (RR, 0.998; 95% CI, 0.997-0.9995) were significantly associated with mortality. In 47 low-bias trials with 180 938 participants, the antioxidant supplements significantly increased mortality (RR, 1.05; 95% CI, 1.02-1.08). In low-bias risk trials, after exclusion of selenium trials, beta carotene (RR, 1.07; 95% CI, 1.02-1.11), vitamin A (RR, 1.16; 95% CI, 1.10-1.24), and vitamin E (RR, 1.04; 95% CI, 1.01-1.07), singly or combined, significantly increased mortality. Vitamin C and selenium had no significant effect on mortality(ref).” Several letters cited on the JAMA website page along with the abstract for this study question the validity of the approach used in the analysis. One such letter written by two doctors at the National Cancer institute states “We believe that the approach used in the meta-analysis of mortality in randomized trials of antioxidant supplements by Dr Bjelakovic and colleagues1 erred in several important ways, probably resulting in biased conclusions(ref).” The implication is that deciding what studies were “low bias risk” was actually an exercise of bias.
Another recent study publication is entitled Antioxidants prevent health-promoting effects of physical exercise in humans. “ Consistent with the concept of mitohormesis, exercise-induced oxidative stress ameliorates insulin resistance and causes an adaptive response promoting endogenous antioxidant defense capacity. Supplementation with antioxidants may preclude these health-promoting effects of exercise in humans.” In a experiment involving 49 healthy young men it was found that “Exercise increased parameters of insulin sensitivity (GIR and plasma adiponectin) only in the absence of antioxidants –“ Also, “ Molecular mediators of endogenous ROS defense (superoxide dismutases 1 and 2; glutathione peroxidase) were also induced by exercise, and this effect too was blocked by antioxidant supplementation(ref).” The study does not deal with the critical question of whether the total impact of both exercising and taking antioxidant supplements is more or less health-producing than exercise or taking antioxidant supplements alone.
Personally I do not know what to make of these two studies except to be open to further research that corroborates or negates the views that they express. I continue to see taking antioxidants as an important part of an anti-aging program. But I stress that taking antioxidants is only one component of what is likely to be an effective anti-aging program such as that identified in my treatise ANTI-AGING FIREWALLS – THE SCIENCE AND TECHNOLOGY OF LONGEVITY. Further, taking certain antioxidants in excess quantities could conceivably be dangerous to health or longevity.