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Men with high blood levels of gamma-tocopherol, a form of vitamin
E not usually found in vitamin supplements, have a reduced risk
for prostate cancer. However, many vitamin E supplements contain
only alpha tocopherol, which can actually lower levels of gamma
tocopherol.
- Researchers looked at blood samples taken from nearly 10,500
men.
- The 20% with the highest levels of gamma-tocopherol were five
times less likely than men with the lowest levels of
the vitamin to get prostate cancer over the next seven years.
Vitamin E is found naturally in vegetable and seed oils, nuts,
whole grains and leafy greens, but levels of the different forms
of vitamin E vary.
Men with high levels of alpha-tocopherol and the mineral selenium,
were less likely to develop prostate cancer only when gamma-tocopherol
was also high, suggesting gamma-tocopherol boosts the power of the
other two antioxidants.
In an editorial accompanying the report, Dr. Edward Giovannucci
of Harvard Medical School in Boston, Massachusetts calls the findings
"further reason for optimism" that vitamin E and other
compounds may fight prostate cancer.
However, he notes that some vitamin E supplements -- mainly alpha-tocopherol
-- can lower blood levels of gamma-tocopherol. According to Dr.
Giovannucci, the average American's bloodstream is five times richer
in alpha-tocopherol than gamma-tocopherol. And, that difference
jumps to 20-fold among people who take
vitamin E supplements.
Since vitamin E supplements may displace gamma-tocopherol, the
researchers conclude, future studies aimed at prostate cancer prevention
should include both forms of vitamin E.
Journal of the National Cancer
Institute, December 20, 2000; 92: 44-49
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