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WASHINGTON (AP), 24.03.2004
Many studies have shown that
starting young mice on a restricted-calorie diet helps them
live for months longer than lab animals fed
a standard diet. But the new research shows that even 19-month-old
mice, about the human equivalent of 60 to 65 years, can have
a longer life when eating fewer calories. The study appears
this week in the Proceedings of the National Academy of Sciences.
Researchers led by Stephen R. Spindler of the University of
California, Riverside, found that restricting calories for
old mice had an immediate benefit in slowing the aging process
and that eventually the animals lived up to six months longer
than their litter mates who were fed the standard diet.
The
diet change added about 42% to the remaining life span of the
calorie-restricted mice when compared with the others, said
Spindler.
It's still unproven that calorie restriction would
extend life in humans as it does in mice, said Spindler, but
if the findings do translate to people "this could mean a lot
more years and a lot of good years. The mice on caloric restriction
live longer and they are healthier."
Spindler said that while
older mice who go on a diet do live longer than those who don't,
they still don't live as long as mice that have been on restricted
diets for a lifetime. He said mice put on low-calorie diets
just after birth have been known to live up to four years,
almost twice as long as normal mice and months longer than
the aged mice in the new study.
The message, he said, is that
sensible eating for a lifetime is best, but there are life
span benefits even if the diet is not started until old age.
"This
is a very important finding," said Dr. George S. Roth of the
National Institute on Aging, one of the National Institutes
of Health.
"The dogma has always been that the earlier in life
you start a restricted diet, the better it works for extending
life," said Roth, a researcher studying the aging process who
was not involved in Spindler's research. "This finding suggests
that you may get some of the same benefits starting late in
life."
Spindler said the study also found that the restricted-calorie
diets also slowed the development and advancement of cancer.
Death from tumors is very common among aged mice, he said,
but the researchers found that tumor growth either started
later or was slowed among mice fed limited calories.
The researchers
also analyzed how the action of genes changed in mice placed
on restricted calorie diets. Spindler said there were changes
and that these might be biomarkers of how the restricted diet
works to extend life.
"People have been searching for 30 years
for biomarkers of the changes that take place during the aging
process," said Spindler. He said the new study in mice suggests
that by measuring gene expression — the amount and type of
proteins made by the genes — scientists could pinpoint the
biomarkers of aging.
Once those are known, he said, it would
be possible to find drugs that have the same effect on life
extension as calorie-restricted diets.
Does this mean that
eventually aging could be slowed by taking a pill? "I am confident
that that day will come," said Spindler.
© 2004
The Associated Press
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