Antioxidants are unlikely to prevent ageing, study suggests
1 December 2008
'Superoxide' free radicals - oxygen molecules that have an imbalance of electrons to protons - are generated in the body through natural processes such as metabolism. These free radicals can cause oxidation in the body, analogous to rust when iron is exposed to oxygen. Biological systems, such as the human body, are usually able to restrict or repair this damage.
In 1956, Denham Harman proposed the theory that ageing is caused by an accumulation of molecular damage caused by 'oxidative stress', the action of reactive forms of oxygen, such as superoxide, on cells. This theory has dominated the field of ageing research for over 50 years. But now, a study published online today in the journal 'Genes and Development' suggests that this theory is probably incorrect and that superoxide is not a major cause of ageing.
"The fact is that we don't understand much about the fundamental mechanisms of ageing," says Dr David Gems from UCL. "The free radical theory of ageing has filled a knowledge vacuum for over fifty years now, but it just doesn't stand up to the evidence."
Dr Gems and colleagues at the Institute of Healthy Ageing studied the action of key genes involved in removing superoxide from the bodies of the nematode worm C. elegans, a commonly used model for research into ageing. By manipulating these genes, they were able to control the worm's ability to 'mop up' surplus superoxide and limit potential damage caused by oxidation.
Contrary to the result predicted by the free radical theory of ageing, the researchers found that the lifespan of the worm was relatively unaffected by its ability to tackle the surplus superoxide. The findings, combined with similar recent findings from the University of Texas using mice, imply that this theory is incorrect.
"One of the hallmarks of ageing is the accumulation of molecular damage, but what causes this damage?" says Dr Gems. "It's clear that if superoxide is involved, it only plays a small part in the story. Oxidative damage is clearly not a universal, major driver of the ageing process. Other factors, such as chemical reactions involving sugars in our body, clearly play a role."
Dr Gems believes the study suggests that anti-ageing products that claim to have antioxidant properties are unlikely to have any effect.
"A healthy, balanced diet is very important for reducing the risk of developing many diseases associated with old age, such as cancer, diabetes and osteoporosis," he says. "But there is no clear evidence that dietary antioxidants can slow or prevent ageing. There is even less evidence to support the claims of most anti-ageing products."
The research was welcomed by Dr Alan Schafer, Head of Molecular and Physiological Sciences at the Wellcome Trust.
“With increasing lifespan comes greater exposure and vulnerability to the ageing process," comments Dr Schafer. "Research such as this points to how much we have to learn about ageing, and the importance of understanding the mechanisms behind this process. This new study will encourage researchers to explore new avenues in ageing research."
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Notes for editors
1. Doonan R et al. Against the oxidative damage theory of aging: superoxide dismutases protect against oxidative stress but have little or no effect on life span in Caenorhabditis elegans. Genes Dev. 30 November 2008 [Epub ahead of print]
2. The Wellcome Trust is the largest charity in the UK. It funds innovative biomedical research, in the UK and internationally, spending over £600 million each year to support the brightest scientists with the best ideas. The Wellcome Trust supports public debate about biomedical research and its impact on health and wellbeing.
3. Founded in 1826, UCL was the first English university established after Oxford and Cambridge, the first to admit students regardless of race, class, religion or gender, and the first to provide systematic teaching of law, architecture and medicine. In the Government's most recent research assessment exercise, 59 UCL departments achieved top ratings of 5* and 5, indicating research quality of international excellence.
UCL is in the top ten world universities in the 2007 THES-QS World University Rankings, and is the fourth-ranked UK university in the 2007 league table of the top 500 world universities produced by the Shanghai Jiao Tong University. UCL alumni include Marie Stopes, Jonathan Dimbleby, Lord Woolf, Alexander Graham Bell and members of the band Coldplay.
4. The UCL Institute of Healthy Ageing (Director: Prof Linda Partridge FRS, CBE) opened in 2007. Its function is to combine work on the new biology of ageing with the study of diseases of ageing and to discover new means to enhance healthy ageing and lifelong wellbeing.