If you've been in a health food store recently, you could not have missed the numerous promotions for antioxidants. For many of these claims, there are no scientific data. For others, study results produce conflicting information.
That's why the National Cancer Institute's newly announced plan for the largest prostate cancer prevention study ever undertaken is so important. The study, labeled SELECT, an acronym for Selenium and Vitamin E Cancer Trial, will begin this summer; it will last 12 years and will involve 32,400 men in the United States, Canada and Puerto Rico. The study will attempt to determine, finally, whether the dietary supplements vitamin E and selenium are effective in reducing the risk of prostate cancer.
Both vitamin E and selenium have antioxidant qualities. Vitamin E is an essential fat-soluble vitamin that helps build normal cells and form red blood cells. Selenium, a mineral found in the soil, is an essential nutrient in small amounts. Antioxidants are chemicals involved in DNA cell maintenance and repair. Some believe that they may help prevent or block carcinogens, or act on cells to suppress cancer development. It is not yet clear, however, that they can actually prevent cancer. The National Library of Medicine lists 1,782 studies of vitamin E and selenium, and more than 86,000 studies of antioxidants in general, with many conflicting results. The SELECT study will carefully examine for the first time the ability of vitamin E and selenium together to prevent prostate cancer. Why were these two elements selected for this major research project? Because prevention trials addressing the ability of selenium and vitamin E to reduce skin and other cancers failed to confirm the expected results but, instead, showed unexpected outcomes: Selenium and vitamin E substantially decreased prostate cancer risk.
Despite the fact that prostate cancer often can be cured, especially when detected early, ( prostate cancer is the second-largest cancer killer of men, after lung cancer. But too many men don't get a simple annual blood test, the prostate specific antigen, or PSA, test, that detects prostate cancer in its early, most curable stages; some other prostate cancers harbor vicious cells that grow despite early detection or proper treatment.
According to the American Cancer Society, this year 198,100 men will be diagnosed with prostate cancer and 31,500 will die of the disease. If selenium and vitamin E prove to reduce the incidence of prostate cancer even by 40% or 50%, tens of thousands of lives would be saved, and thousands more would be spared the grief of diagnosis and treatment.
There's another good reason to conduct the SELECT trial. Antioxidant supplements are broadly promoted, often with little scientific support, for the prevention and treatment of heart disease, diabetes, high blood pressure, cancer and other conditions. Sometimes, what appears logically certain turns out to be just the opposite. Everyone was convinced, for example, that beta carotene, the important antioxidant responsible for the orange color of carrots, would have major health benefits. However, beta-carotene supplements, tested in several large studies, have not produced benefits. In fact, a groundbreaking randomized study of more than 29,000 male smokers found that beta-carotene supplements given to prevent lung cancer actually had harmful effects.
Especially given the contradictory results of numerous past investigations, proper evaluation of the benefits of vitamin E and selenium requires precisely the large, long-term, well-done prospective study that the SELECT project will be.
What is clear is that claims for cures and successful preventive measures of any illness or disease need proper testing under carefully controlled conditions before we can safely use or depend upon them. While we await the results of the long-term SELECT trial, remember that many studies support the connection between carotene-rich foods and good health, while supplements show no benefit or actual harm. We have not yet learned how to stuff into a capsule the only partially understood active ingredients in these beneficial foods. You will receive an adequate and probably more effective supply of most antioxidants by including generous amounts of fruits and vegetables, including broccoli, Brussels sprouts, cabbage, cauliflower, carrots, yams, cantaloupe, tomatoes, red grapefruit, and so on, in your daily diet.
Until we know for sure, don't depend on food supplements to prevent prostate or any other kind of cancer.