Wednesday, June 3, 2009

Current defense strategies from reactive oxygen species (ROS)

The traditional strategy of combating free radicals is based on counteracting ROS with antioxidants, free-radical scavengers or readily oxidizable substances acting as free-radical captors. Common antioxidants include vitamins (vitamin C, vitamin E), carotenoids (β-carotene, lycopene) and microelements (zinc and selenium; the latter can also enhance the body's own repair pathways). To prevent ageing and age-related diseases, these compounds are usually taken as dietary supplements, which are widely used in industrialized countries.

It is thought that such nutraceuticals protect human cells and tissues from the damaging effects of oxidation. Many nutraceutical and health-food companies are now involved in the production and distribution of antioxidant-containing dietary supplements. However, despite widespread public optimism about the likely beneficial anti-ageing effects of antioxidants, so far there is no solid proof that use of antioxidants can stop or reverse the ageing process. Although some researchers claim that antioxidant supplements do show positive results in the battle against ageing, others have not identified any statistically significant benefit from the use of antioxidants. Some studies indicate that dietary antioxidants might only be effective in men because their bodies are somewhat lower in the contents of certain antioxidants, for example, β-carotene, than women's bodies.

However, the amounts in which these antioxidants should be consumed to be truly beneficial without being harmful has to be carefully considered, especially for elderly or other vulnerable populations. Indeed, by modulating cellular redox status, an optimal ROS level could be very important in homeostasis of aerobic life. In this regard, a recent study has come to a shocking conclusion: treatment with β-carotene, vitamin A and vitamin E might actually increase mortality! This study also concluded that the potential roles of vitamin C and selenium in longevity in humans need further investigation.

The contradictory results obtained with antioxidants as anti-ageing agents make it clear that alternative approaches are needed. A fresh look at the old problem has just been taken from the chemical kinetics viewpoint.

Vadim V. Demidov (2007) Heavy isotopes to avert ageing?
Trends in Biotechnology, Volume 25, Issue 9, September 2007, Pages 371-375

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