Does Vitamin D Deficiency Increase Prostate Cancer Risk? A Systematic Review of the Literature

Background: The concept that cancer incidence and mortality are related to latitude was first suggested in 1930. Since then, there have been a plethora of studies addressing that connection. Studies of vitamin D have demonstrated its anti-proliferative, anti-angiogenesis and differentiating properties which are all anti-neoplastic. The relationship between prostate cancer and latitude has long been suspected. Prostate cells have vitamin D receptors and enzymes for hydroxylation of vitamin D metabolites and enabling anti-carcinogenetic effects. As a result of these findings, many ongoing studies are evaluating whether vitamin D deficiency impacts prostate cancer risk. This review summarizes the last two years of published studies on this topic. Methods: The search used Ovid/Medline, PubMed, CINAHL and Web of Science databases limited to include clinical studies, English language, major journals and including articles from 2007 to the present. Review of the abstracts produced the relevant studies, and the bibliographies of these articles led to other sources not found in the search. Keywords: prostate cancer, risk, vitamin D and vitamin D deficiency. Results: Five studies reviewed from the end of 2007 to the present were germane to the research topic. One study was an observational study, one a prospective study and the remainder were case control studies from much larger randomized controlled trials. Only one case reviewed the relationship between solar radiation and prostate cancer risk and all the relationships were positive for low solar radiation and higher prostate cancer risk. Three studies reviewed the relationship of serum levels of vitamin D and prostate cancer risk relative to polymorphisms of the VDR and two found that low levels of serum vitamin D increase prostate cancer risk, especially aggressive prostate cancer risk. One large study examining serum concentrations of only one vitamin D metabolite found no association with PCa. Conclusions: Vitamin D deficiency is a widespread health issue. There is an increased risk of prostate cancer with low vitamin D levels.The risk is greater with more aggressive disease. Conflicting results regarding PCa risk and VDR polymorphisms in light of low vitamin D levels, and it may be a one-time serum sample which causes these discrepancies. There is an association between solar radiation and PCa risk, need to follow the serum levels or solar exposure of patients much younger. Both metabolites need to be measured to understand the impact on prostate cancer risk, especially since the data shows an increased risk with aggressive disease with the one typically not measured. One serum sample does not provide information needed for understanding the relationship between vitamin D and PCa. More prospective studies beginning at an earlier age with more serum samples and solar radiation studies are needed in order to better understand the relationship between prostate cancer and vitamin D