Vitamin D promotes the differentiation of
prostate cancer cells, raising the possibility that
vitamin D deficiency over time may contribute to the progression from subclinical
prostate cancer to clinical disease. Since low-risk
prostate cancers are monitored over time in an effort to determine which progress into clinically important, more aggressive
cancers, they provide an excellent model in which to study, over an extended period of time, the effects of enhancing
vitamin D status and related changes in
tumor progression. This is particularly relevant to African-American men, who exhibit a high prevalence of
vitamin D deficiency as well as higher incidence of
prostate cancer and higher mortality rates from
prostate cancer than Caucasians. Our research team has recently completed an open-label clinical trial aimed at assessing the safety and potential efficacy of
vitamin D3 supplementation at 4000 international units (IU) per day for one year in subjects diagnosed with early stage, low-risk
prostate cancer. The results of this clinical study suggest that supplementation with
vitamin D3 at 4000IU per day may benefit patients with early stage, low-risk
prostate cancer on active surveillance, because of the improved outcome (a decreased number of positive cores at repeat biopsy) in more than half of the subjects enrolled in the trial. We also observed that, after one year of supplementation, there was no difference in circulating levels of
vitamin D between African-American and Caucasian subjects who completed the study. These clinical results also suggest that robust and sustained
vitamin D3 supplementation can reduce
prostate cancer-related health disparities in African-American men and that these health disparities are at least in part the result of widespread hypovitaminosis D within the African-American population. This article is part of a Special Issue entitled '
Vitamin D Workshop'.