The underlying cause of prostate cancer is unknown. As with other cancers, however, multiple events over a period of many years are probably necessary to produce a cancerous change in a prostate cell. A recent study links overuse of multivitamin supplements with the risk of fatal prostate cancer.
The development of cancer is broadly viewed as a two-step process. The first step is initiation, when the cell is exposed to substances (such as a chemical), agents (such as a virus), or forces (such as radiation) that cause an alteration (mutation) in the genetic machinery of the cell. The second step is promotion, in which other chemicals, hormones, or diet and lifestyle patterns stimulate the growth and reproduction of the abnormal cell. A promoter does not set the process in motion, but it creates an environment favorable for the runaway growth that causes a cancerous tumor to form and progress.
Now a study reported in the Journal of the National Cancer Institute (Volume 99, page 754) sheds light on a possible new promoter: excessive use of multivitamins.
The study analyzed information on multivitamin and supplement use in nearly 300,000 men enrolled in the National Institutes of Health-AARP Diet and Health Study. Researchers gathered information on diet and use of multivitamins and other supplements.
All men were cancer free at enrollment. But over the next five years 10,241 developed prostate cancer, 8,765 had localized disease (cancer that has not spread beyond the gland), and 1,476 had advanced cancer. Six years later, 179 men had died of their cancer.
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No link between multivitamin use and the development of localized prostate cancer was seen. But men who took multivitamins more than seven times per week had double the risk of fatal prostate cancer. The risk was highest among men with a family history of prostate cancer and those who also took individual supplements of selenium, zinc, or beta-carotene.
The bottom line: One multivitamin a day isn’t a problem, but don’t take more than that, and be cautious about adding individual supplements since they may provide the intended micronutrient in "macro” amounts.
