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Antioxidants are
unlikely to prevent aging, study suggests
Diets and beauty products which claim to
have anti-oxidant properties are unlikely to
prevent ageing, according to research funded
by the Wellcome Trust.
Researchers at the Institute of Healthy
Ageing at UCL (University College London)
say this is because a key fifty year old
theory about the causes of ageing is wrong.
"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 fifty years. But
now, a study published online today in the
journal Genes & 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 which claim to have
anti-oxidant 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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