Excessive Zinc Supplementation May Increase Prostate Cancer Risk
Laurie Barclay, MD
July 1, 2003 — Zinc supplementation may increase prostate cancer risk, according to the results of a study published in the July 2 issue of the Journal of the National Cancer Institute. Reviewing data from the Health Professionals Follow-up Study, the investigators suggest that zinc supplementation of 100 mg/day or more or use of supplements for more than 10 years can more than double the risk of prostate cancer.
"The high concentration of zinc in the prostate suggests that zinc may play a role in prostate health," write Michael F. Leitzmann, MD, from the National Institutes of Health in Bethesda, Maryland, and colleagues. "Whether dietary zinc intake affects intraprostatic zinc levels is unknown. However, ingestion of 150 mg/day or more of zinc has undesirable metabolic effects, such as immune dysfunction and impaired antioxidant defense that are potentially related to prostate cancer."
During follow-up from 1986 through 2000 of 46,074 U.S. men enrolled in the Health Professionals Follow-up Study, 2,901 developed prostate cancer, including 434 cases of advanced cancer.
Although supplemental zinc up to 100 mg/day was not associated with prostate cancer risk, men who consumed more than 100 mg/day of supplemental zinc had more than double the risk of advanced prostate cancer compared with nonusers (relative risk, 2.29; 95% confidence interval [CI], 1.06 - 4.95; P = .003 for trend). In men who used zinc supplements for at least 10 years, relative risk was 2.37 (95% CI, 1.42 - 3.95; P <.001 for trend).
"Excessively high zinc intake was associated with an increased risk of advanced prostate cancer," the authors write. "Although we cannot rule out residual confounding by supplemental calcium intake or some unmeasured correlate of zinc supplement use, our findings, that chronic zinc oversupply may play a role in prostate carcinogenesis, warrant further investigation."
J Natl Cancer Inst. 2003;95:1004-1007
Reviewed by Gary D. Vogin, MD
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