Re: Vitamin and mineral use and risk of prostate cancer: the case–control surveillance: Zhang et al. Cancer Causes Control. 2008 Dec 18 [Epub ahead of print]

Addendum

During the editorial review process of this submission, a new important and relevant report¹ had appeared. The results of this new report are at odds with Zhang et al. conclusions. The authors, Gonzalez et al. described that, “An advantage of our cohort is that it was specifically designed to investigate the association of supplement use with cancer risk and accordingly includes a large proportion of high users of dietary supplements. We have a more detailed exposure assessment than other studies, including exact composition of multivitamins and information on use of single zinc supplements.” The major conclusion of the study is that, “the risk of advanced prostate cancer decreased with greater intake of supplemental zinc for 10-year average intake >15 mg/day versus nonuse.” The authors also found that dietary zinc intake was not associated with prostate cancer risk; and observed other weak associations of supplemental zinc use with a reduction of prostate cancer. They conclude that, “If future studies support these results, it may suggest that zinc supplements may be beneficial for some subgroups of men or for the most adverse forms of the disease.”

The relevance of the Gonzalez et al. report is that it substantiates the concerns that we have presented in this communication and in our previous critiques of the studies and conclusions of epidemiologic studies. Gonzalez et al., carefully review and contrast their study and the divergent observations and conclusions with those of other epidemiology reports. The study re-affirms our view that there is no consistent basis at this time for any definitive conclusion regarding the role or influence of dietary/supplemental zinc on the development and progression of prostate cancer. It is and has been a disservice and adverse to the interests of the medical, scientific, and pubic communities to promote any proclamations of beneficial or adverse effects of dietary/supplemental zinc on the incidence of prostate cancer.