Vitamin E and beta-carotene were chosen because epidemiologic studies have linked high dietary intake and high serum levels of these micronutrients to a reduced risk of cancer, particularly lung cancer. Both are antioxidants, compounds that may prevent carcinogens from damaging DNA . The mechanisms by which vitamin E may reduce prostate cancer risk are not clear. Vitamin E is an antioxidant. The men in the study took one pill each day, which contained vitamin E, beta-carotene, both, or neither.
Vitamin E is found mainly in oils, such as vegetable oils, and in nuts and grains.
The amount in the U.S. diet varies, but is estimated to be about 17 mg per day. NCI has never recommended that Americans take supplements. The results of the ATBC Study, while promising, do not answer whether vitamin E supplements would be able to reduce the risk of prostate cancer in men of varying race and ethnicity and in nonsmokers. For all Americans who wish to reduce their risk of cancer, a low-fat diet with plenty of fruits, vegetables, and whole grains remains the choice to make. NCI has a number of different agents under study, including calcium , fiber, tamoxifen , finasteride , and others.