Targeting free radicals to slow aging

Because of the strong association between oxidative stress and aging, as well as a range of age-related diseases, it makes perfect sense to target free radicals as a means to slow aging. Almost all anti-aging strategies for the last 30 years have included high doses of antioxidants as a central ingredient.

The problem is that although the idea of antioxidants is sound, the long-term effects on health and longevity are yet to be realized or understood.

Unequivocally, diets naturally high in antioxidants can both prolong life and reduce the effects of aging and have done so for centuries.  However, with a few exceptions, clinical trials with antioxidant supplements have not demonstrated the advantages of dietary sources. Indeed some antioxidants have proven to be harmful to human health.

So why the difference between antioxidants from supplements and antioxidants from food?

  • Firstly, the antioxidants most commonly used in clinical trials (Vitamins A, C, E and carotene) are not very selective in their actions and have other effects on the human body, particularly in high doses. Some can actually generate free radicals!
  • Secondly, most studies were not specifically performed in individuals with high levels of oxidative stress. It is possible that participants in these trials did not benefit simply because reduced antioxidant defense was not their problem.
  • Thirdly, it may be that other components of a diet naturally rich in antioxidants contribute to their benefits. These may include a range of polyphenols and pathway intermediates, such as lycopenes. It may also be that different dietary elements have a greater effect when coupled together. Indeed, a basic principle of traditional medicine is that complex conditions are best managed by complex medicines. In order to capture the different defense and protective actions, a ‘brew’ often contained extracts from a range of different sources. In the same way, the health benefits of tomatoes are more than the sum of its lycopenes. Citrus is not just Vitamin C, but also rutin, other antioxidant bioflavonoids and a host of other ingredients.
  • Finally, it may be too much to ask of a supplement to get into each cell, and especially each mitochondria of each cell, to reduce ROS levels. Neither Vitamin A, C or E actually inhibit production of ROS. They only clean up after the fact, by which time the damage may have already been done or molecules are generated that are immune to the scavenging effects of these antioxidants. To this end, more specific interventions to reduce radical formation, like selenium supplements, may prove more useful than non-specific ‘after the fact’ scavengers.

Last Reviewed 02/Mar/2014


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Dr Merlin Thomas

Professor Merlin Thomas is Professor of Medicine at Melbourne’s Monash University, based in the Department of Diabetes. He is both a physician and a scientist. Merlin has a broader interest in all aspects of preventive medicine and ageing. He has published over 270 articles in many of the worlds’ leading medical journals

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