Vidyya Medical News Service
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Volume 6 Issue 89 Published - 14:00 UTC 08:00 EST 29-Mar-2004 Next Update - 14:00 UTC 08:00 EST 30-Mar-2004
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Higher serum α-tocopherol and γ-tocopherol concentrations are associated with lower prostate cancer risk

Two forms of vitamin E - α- and γ-tocopherol - appear to lower the risk of prostate cancer by as much as 53 percent and 39 percent, respectively, based on the findings of a team of scientists from the National Cancer Institute, the Fred Hutchinson Cancer Research Center in Seattle and the National Public Health Institute of Finland.

The researchers, led by Stephanie J. Weinstein, M.S., Ph.D., and Demetrius Albanes, M.D., of the NCI Nutritional Epidemiology Branch, Division of Cancer Epidemiology and Genetics, drew their subjects from the α-Tocopherol, Beta-Carotene Cancer Prevention Study cohort of 29,133 Finnish men, aged between 50 and 69 years. From that group were selected 100 men with prostate cancer and 200 without, to determine whether there exists an association between higher levels of α-tocopherol and γ-tocopherol circulating in the blood stream and lower risks of prostate cancer. The ATBC Study previously had demonstrated a 32 percent reduction in the rate of prostate cancer among men who took 50 mg of α-tocopherol per day for a period of five to eight years.

Since the baseline value for serum levels of α-tocopherol and γ-tocopherol in this study came from blood drawn before men in the ATBC trial started taking any pills, use of vitamin E supplements was a factor only if the participants had been taking them already. Ten percent had, leaving 90 percent whose serum levels of α-tocopherol and γ-tocopherol could be attributed exclusively to dietary intake. In addition, in keeping with earlier findings, the men who were randomized to receive a vitamin E supplement as part of the ATBC trial and who had the highest serum vitamin E levels at baseline displayed the lowest risk of prostate cancer.

"Nuts and seeds, whole grain products, vegetable oils, salad dressings, margarine, beans, peas and other vegetables are good dietary sources of vitamin E," Weinstein said.

She explained the striking difference in the relative amounts of α-tocopherol and γ-tocopherol in the body compared to dietary contents.

"Even though γ-tocopherol is by far more prevalent in U.S. diets," noted Weinstein, "α-tocopherol is found in greater concentrations in the blood. That is at least in part because a protein in the liver called α-tocopherol transfer protein preferentially binds α-tocopherol and secretes it into the plasma."

Weinstein further noted that one principal dietary difference between Finns and Americans is the type of cooking oils used. "The Finns generally eat more canola oil," she said, "while Americans favor corn or soybean oils. Canola oil is richer in α-tocopherol and offers the added benefit of being lower in saturated fat."

To achieve optimum serum levels of α- and γ-tocopherols, Weinstein recommends following the Dietary Guidelines for Americans, published by the U.S. Department of Agriculture and the U.S. Department of Health and Human Services. They call for eating more fruits, vegetables and whole grains, and fewer fats and sugars.


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