Objectives: Zinc concentration is higher in the prostate than in most other tissues. Since information on the role of zinc on prostate carcinogenesis is controversial, we analysed the issue in a case-control study.
Methods: Between 1991 and 2002, we conducted a multicentre hospital-based case-control study on prostate cancer in Italy. Cases included 1294 men with incident, histologically confirmed prostate cancer. Controls included 1451 patients admitted to the same hospitals as cases for a wide spectrum of acute non-neoplastic, non-hormone-related diseases. Zinc intake was computed from a valid and reproducible food frequency questionnaire, with the use of an Italian food composition database. Odds ratios (OR) of dietary intake of zinc and the corresponding 95% confidence intervals (CI) were estimated by unconditional multiple logistic regression models, after allowance for several covariates, including total energy.
Results: Compared with the lowest quintile, the OR for the highest quintile was 1.56 (95% CI, 1.07-2.26), with a significant trend in risk (p=0.04). The trend in risk was significant for advanced cancers only, the OR being 2.02 (95% CI, 1.14-3.59) for prostate cancers with a high Gleason score.
Conclusions: In this large study we found a direct association between high zinc intake and prostate cancer risk, particularly for advanced cancers. Our findings allow one to exclude a favourable effect of zinc on prostate carcinogenesis.