Diet Rich in Vitamins C, E May Pare Alzheimer's Risk
By: Susan Okie
Washington Post, June 26, 2002
Eating a diet rich in vitamin E and vitamin C may
lower the risk of developing Alzheimer's disease, according to two studies
released yesterday.
The studies, from the United States and the
Netherlands, both found evidence to suggest that high vitamin E intake
from food -- although perhaps not from supplements -- could reduce the
risk of the degenerative brain disease. The Dutch study also found that a
diet high in vitamin C was associated with a lower risk of Alzheimer's.
Both vitamins are antioxidants, which help protect
the body's cells from damage by free radicals, harmful substances
generated during normal metabolism. Researchers believe that a gradual
buildup of cell damage caused by free radicals is a factor in aging and
probably contributes to the development of Alzheimer's.
The findings offer some of the first evidence in
humans that antioxidants may help protect healthy people against
Alzheimer's, although research in animals has suggested that antioxidants
can prevent age-related changes in the brain. A previous trial found that
high-dose vitamin E supplements could slow the rate of decline in
Alzheimer's patients.
"We know that antioxidant nutrients work as a
defense network," said Jeffrey Blumberg, a professor of nutrition at
Tufts University. "It makes sense that antioxidants like vitamin E
and C, over the long term, help to reduce the risk."
In the U.S. study, the frequency of Alzheimer's
disease among participants with the highest level of dietary vitamin E
intake was 70 percent lower than among those with the lowest intake.
"I think it's very interesting that studies in
two different countries, with two different types of diets, showed the
same nutrient to be protective," said Martha Clare Morris, an
epidemiologist at Chicago's Rush Institute for Healthy Aging, who led the
project.
Good sources of vitamin E include nuts, seeds,
vegetable oils, whole grains, green leafy vegetables and cereals fortified
with vitamin E. Vitamin C is abundant in fruits and vegetables, especially
citrus fruits.
While Morris cautioned consumers against rushing out
to buy dietary supplements, some other experts said supplements might be a
reasonable choice for some people.
"I think it's important that we not discourage
people from using vitamin E and C supplements, so long as they are using
them well, with discussions with their doctors about . . . how much
they're taking," said Daniel E. Foley of the National Institute on
Aging.
In the studies, published in today's issue of the
Journal of the American Medical Association, researchers monitored the
health of a large group of older people after questioning them extensively
about their diet, use of supplements and other lifestyle factors.
Because of their design, the studies cannot prove
that high intakes of vitamins E or C caused a reduction in Alzheimer's
rates. Experts hope that definitive proof will come from ongoing studies
in which groups of elderly people are randomly assigned to take vitamin E,
vitamin C or various other dietary supplements and are then compared with
others assigned to take a placebo to see which groups have lower rates of
Alzheimer's disease. Results are not expected for five to seven years,
said Neil Buckholtz,chief of the dementias of aging branch of the National
Institute on Aging.
Meanwhile, the findings underscore the importance of
a healthy diet and especially of vitamin E intake. "Americans do not
meet their requirements for vitamin E," in part because some of the
best sources are vegetable fats that many people have tried to cut down
on, Blumberg said.
U.S. women typically consume between 50 percent and
70 percent, and men about 75 percent, of the recommended daily allowance
(currently 15 milligrams), he said. In contrast, Americans' average intake
of vitamin C exceeds the recommended daily allowance of 75 milligrams for
women and 90 milligrams for men.
In the Dutch study, researchers enrolled 5,395
residents of Rotterdam who were over 54 years old, obtaining information
on diet and many other factors. During a six-year follow-up period,
participants underwent regular mental status examinations and were seen by
a neurologist if dementia was suspected.
A total of 146 participants developed Alzheimer's
disease. High dietary intakes of vitamins E and C (but not taking
supplements) were both associated with lower rates of Alzheimer's,
especially among smokers, who are at higher risk of the disorder than
non-smokers. In smokers (but not in non-smokers), high intakes of beta
carotene and flavonoids -- other kinds of antioxidants -- were also
associated with a reduced risk of Alzheimer's.
In the U.S. study, 815 Chicago residents over the age
of 64 were questioned about their diet and other factors and were followed
for an average of four years. About half of the study participants were
white and half were black. A total of 131 participants developed
Alzheimer's disease. High dietary intake of vitamin E, but not vitamin E
supplements, was associated with lower rates of Alzheimer's. However, the
protective effect of the vitamin was not seen in people (about one-third
of participants) who carried a gene called APOE epsilon 4 that is
associated with a higher risk of the disorder.
Experts said the fact that the studies found benefits
from dietary vitamin E and C but not from vitamin supplements does not
necessarily mean that supplements are ineffective. The rates of supplement
use in the studies were relatively low, and use was often recent.
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