Vitamin E and Prostate Cancer: Current Evidence and Future Directions

Vitamin E has been hypothesized to protect against prostate cancer. The anti-carcinogenic activity of vitamin E is attributed in large part to its potent antioxidant activity - it is the major hydrophobic chain-breaking antioxidant that protects membrane lipids from oxidation. In addition, vitamin E has several important non-antioxidant functions, including inhibition of protein kinase C (PKC) activity, which plays an important role in proliferation, adhesion, immune response, free radical production, and gene expression. Vitamin E also appears to interfere with hormone signaling, which is particularly relevant to prostate carcinogenesis. The concept that common SNPs in genes encoding for proteins responsible for uptake, transport, and delivery of tocopherols and tocotrienols to the prostate may impact upon prostate cancer risk has not been examined and warrants future research. Overall, substantial evidence from mechanistic studies shows a protective effect of vitamin E on prostate carcinogenesis. However, results from observational epidemiologic studies regarding the association between vitamin E and prostate cancer risk are mixed. The available data suggest that vitamin E may more strongly protect against advanced than early-stage prostate cancer, and that the apparent beneficial effect of vitamin E on prostate cancer may be more pronounced among cigarette smokers. At present, the most prudent strategy for prostate cancer prevention regarding vitamin E intake is to adhere to the current U.S. dietary guidelines, which recommend eating a well-balanced diet that is rich in a variety of fruits, vegetables, and whole grains.