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Individuals with high blood levels of vitamin C, as
well as those who consume a lot of vegetables, have significantly reduced
risk of stroke, according to a just published long-term study.
"To my knowledge, this is the first prospective study to make the
correlation between vitamin C in the bloodstream and incidence of stroke,"
says author Tetsuji Yokoyama, M.D., research associate in epidemiology
at the Medical Research Institute of Tokyo Medical and Dental University.
"The risk of stroke was inversely
related to vitamin C in the bloodstream and frequency of vegetable consumption."
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The researchers examined 880 men and 1,241 women
in rural Japan, which were divided into four groups according to the
level of vitamin C in their blood.
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Among the participants, 196 strokes occurred
during a 20-year period beginning in 1977.
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"The risk of stroke was 70 percent higher
among those in the lowest quarter than those in the highest,"
says Dr. Yokoyama.
When researchers examined strokes based on the number
of days per week the participants ate fruits and vegetables, they found
a similar relationship. The clearest association was
for vegetable consumption.
"The risk of
all types of stroke was 58 percent lower among those who consumed vegetables
six to seven days per week, compared to those who only consumed
them up to two days a week," notes Dr. Yokoyama.
The 196 strokes that occurred included:
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109 cerebral infarctions - a stroke in
which blood flow to the brain is blocked
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54 hemorrhage strokes, which occur when
an artery in the brain bursts
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33 strokes which were of undetermined typed.
Because a risk reduction was observed in both types
of stroke, Dr. Yokoyama says the responsible mechanism
probably extends beyond vitamin C's known antioxidant effects.
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Cerebral infarctions
are considered to be the result of atherosclerosis, the build-up of
fatty deposits in arteries. Antioxidants can prevent the buildup.
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Hemorrhagic stroke
results from a ruptured blood vessel in the brain.
The researchers are preparing a database to analyze
the association between blood levels of vitamin C and subsequent incidence
of heart attack in the same population.
Stroke October,
2000; 31: 2287-94.
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