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.

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