Use of Nutrition Supplements Discouraged for Men with Prostate Cancer

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Nutritional supplements and alternative therapies are becoming increasingly popular for both the prevention and treatment of many types of cancer. However, many patients tend to use dietary supplements without discussing them as an overall treatment plan in addition to medical therapies. In the case of some cancer treatments, certain supplements are not advised because they interfere with therapies such as radiation.

In the case of prostate cancer, supplements are marketed to men who have had unpleasant side effects associated with treatment such as impotence. Researchers from William Beaumont Hospital published a study in the March issue of the International Journal of Radiation Oncology discouraging the practice.

Brian Marples, PhD, senior author of the study and radiobiologist, and colleagues researched published reports on three widely used commercial dietary supplements promoted for prostate health. Other studies have found that these may have negative effects for some tumor sites after the use of chemotherapy, but the interaction with radiation therapy was not well-known, although preliminary studies indicate an interference with the treatment.

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The researchers found that radiosensitivity – the susceptibility of the cell to respond to radiation - of the malignant cells were not affected; however two of the supplements inhibited the growth rate of the normal prostate cell lines. This can lead to complications in the normal prostate tissue. The third supplement increased cellular radiosensitivity of some normal cell lines by inhibiting DNA repair.

Although doctors are concerned about men with prostate cancer who take extremely high doses of nutrition supplements and its potential for negative effects on treatment, it appears that taking a standard multivitamin may be okay to take with the physician’s approval. A small study on 52 men presented at the American Society for Radiation Oncology in November 2009 did not find harmful effects of normal levels of vitamin or antioxidant supplementation on radiation therapy for prostate cancer, however they also did not find a significant benefit in the treatment. Men who took a standard multivitamin had no difference in PSA response than those not taking supplements.

Dr. Zietman, of the Harvard Medical School in Boston who conducted the study, did say that men taking supplements marketed specifically for prostate health may inadvertently be getting hormonal therapy. Some dietary supplements may contain phytoestrogens or synthetic hormones which may stimulate the growth of the cancer cells.

"Cancer patients turn to supplements to aid in their treatments for a variety of reasons, but this study proves that what some patients believe is helping them may actually be harming them," said Dr. Marples. "It is very important for all patients to discuss any type of supplement they may be taking with their physician and especially important for prostate cancer patients receiving radiation therapy as this study shows that it may be negatively affecting the effectiveness of their treatments."

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