Posted on February 6th, 2009 by
According to the American Cancer Society, one in six men in the United States will be diagnosed with prostate cancer within their lifetime. Due to the prevalence of prostate cancer, preventing its development altogether has been studied extensively.
Several studies have reported that higher intake of fruits and vegetables may reduce the risk of certain types of cancer. This has prompted interest in whether dietary supplements (such as multivitamins) that provide some of the antioxidant micronutrients found in fruits and vegetables may also reduce cancer risk. Approximately one-third of all individuals in the United States take multivitamins regularly—often in the hopes of preventing disease such as cancer. There is limited evidence that antioxidant supplements reduce cancer risk, however, and some studies have even suggested that they may increase cancer risk in certain populations. Research continues in this area to determine the effects of supplementation.
The first study, published in Cancer Epidemiology, Biomarkers and Prevention, involved over 28,000 men who did not have prostate cancer at the beginning of the study; their blood levels of lycopene and beta-carotene were tested. After a follow-up of approximately eight years, it was found that rates of prostate cancer in men with the highest levels of lycopene did not differ from those with the lowest levels of lycopene. Furthermore, among men diagnosed with prostate cancer, cancer was not less aggressive in those with the highest levels of lycopene in the blood compared with men with the lowest levels of lycopene.
It was also found in this study that men with high levels of beta-carotene, another antioxidant, in the blood actually had an increased risk of developing prostate cancer. In addition, compared with those with prostate cancer and lower levels of beta-carotene, men with prostate cancer who had high levels of beta-carotene had a more than threefold increased risk of having prostate cancer that had spread to distant sites in the body.
These researchers acknowledge that this study may have limitations due to the fact that just one blood sample was used (at the initiation of the trial) and at eight years, the follow-up was relatively short. However, it appears that lycopene and beta-carotene do not protect, at least in the short-term, against the development of prostate cancer.
In a second study, published in the Journal of the National Cancer Institute, results indicated that large doses of multivitamins not only do not protect against developing prostate cancer but may actually increase the risk of developing fatal prostate cancer.
To assess the relationship between multivitamin use and risk of prostate cancer, researchers evaluated information from the National Institutes of Health (NIH)-AARP Diet and Health Study. The study enrolled 295,344 men who were free of cancer at the start of the study.
During five years of follow-up, prostate cancer was diagnosed in 10,241 of the study participants. The prostate cancer was localized (confined to the prostate or near the prostate) in 8,765 cases and advanced (spread from the prostate) in 1,476. There were 179 prostate cancer deaths.
The researchers conclude, “The possibility that men taking high levels of multivitamins along with other supplements have increased risk of advanced and fatal prostate cancers is of concern and merits further evaluation.” An accompanying editorial notes that these results “add to the growing evidence that questions the beneficial value of antioxidant vitamin pills in generally well-nourished populations and underscore the possibility that antioxidant supplements could have unintended consequences for our health.”
On a promising note, however, a third study indicated a reduction in the risk of developing prostate cancer with the use of the cholesterol-lowering drugs referred to as statins. Researchers from Finland recently conducted a study evaluating the effects of statins on the incidence of prostate cancer. This study included over 22,500 men who had undergone screening for prostate cancer. Approximately 5,060 men were statin users, and 17, 478 men did not use statins.
In summary, these three studies indicate that lycopene, beta-carotene, and large doses of multiple vitamins do not provide protection against the development of prostate cancer; however, the use of statins may provide a protective effect.
It is important to note that there are several issues surrounding these studies that may affect their results. For example, vitamin supplements are not regulated by the Food and Drug Administration (FDA), and may contain trace amounts of substances that may contribute to the development of cancer. In addition, results indicating lycopene does not provide a protective effect against the development of cancer conflicts with findings from other studies evaluating this issue. Finally, the use of statins may mask the existence of some prostate cancers, as their use may lower PSA levels in comparison with men who don’t take statins. Longer follow-up from these studies, as well as additional studies, will provide further information. Until then patients are encouraged to discuss supplement use and screening schedules for prostate cancer with their physician.
 Peters U, Leitzmann MF, Chattrerjee N, et al. Serum lycopene, other carotenoids, and prostate cancer risk: a nested case-control study in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Cancer Epidemiology Biomarkers and Prevention. 2007; 16:962-968.
 Lawson KA, Wright ME, Subar A et al. Multivitamin use and risk of prostate cancer in the National Institutes of Health-AARP Diet and Health Study. Journal of the National Cancer Institute. 2007;99:754-64.
 Teemu J, Teuvo LJ, Maattanen L, Auvinen A, Statins and prostate cancer among men participating in the Finnish prostate cancer screening trial. Proceedings of the 2007 meeting of the American Urological Assoication 2007; Abstract #1719. http://www.abstracts2view.com/aua/index.php
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Tags: Prostate Cancer
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