During metabolism a small proportion of oxygen is converted into toxic products, collectively known as Reactive Oxygen Species (ROS or free radicals). When attacked by free radicals,  proteins, DNA and lipids don’t work as they should so function declines. As we get older and our systems for metabolizing oxygen become less efficient, our production of free radicals increases.  If the production of free radicals outstrips our (antioxidant) defense mechanisms, a state of oxidative stress is said to exist.

Oxidative stress is one of the most important elements of the aging process. There is a lot we can do to bolter our antioxidant defenses, as well as erode them prematurely. Unequivocally, diets naturally high in antioxidants can improve health and  prolong life and have done so for centuries.

Will anti-antioxidant supplements slow the aging process?

Almost all anti-aging strategies for the last thirty 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 proved to be harmful for human health.

So, why the difference between antioxidants from supplements versus those from food?

    • Firstly, the antioxidants most commonly used in clinical trials (Vitamin A, C, E and carotene) are not very selective in their actions and have other effects on the human body, particularly in high doses
    • 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.
    • Finally, it may be that is 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 inhibits the production of ROS. They only clean up after the fact, by which time 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.

What can we do then?

In other articles, we look in detail at the most common antioxidants that are available as supplements and the evidence for and against their actions to slow aging. There is not data on which is the best of these many antioxidants when taken as supplements. Each of these will have their own supporters. It may be that, like the computer we will be kicking ourselves for not investing earlier. Some may also turn out to be a waste of money.

Last Reviewed 03/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