Vitamin D as a chemopreventive agent in colorectal neoplasms. A systematic review and meta-analysis of randomized controlled trials.

Colorectal cancer (CRC) is the third most common cancer in both sexes and the second in terms of mortality. Apart from genetic predisposition, dietary and lifestyle factors have been implicated in the development of CRC. Several studies suggested that vitamin D (VitD) might be a promising strategy in CRC prevention, while other studies did not confirm this finding. The aim of our study was to examine the role of Vit-D supplementation in the prevention of colorectal neoplasms (CRC and polyps). We conducted a systematic search in Pubmed, Embase and Web of Science databases for Randomized Controlled Trials (RCTs) examining the incidence of colorectal neoplasms in patients taking Vit-D supplementation compared to placebo. We synthetized results using Risk Ratio along with 95% Confidence Intervals (CIs). Nine RCTs (N = 71,386) were included. Non-significant correlations were observed between Vit-D supplementation and CRC incidence (RR:1.06, p = 0.52). Similarly, non-significant associations were observed between the use of Vit-D supplements and colorectal adenoma incidence (RR:1.00, p = 0.91). Advanced adenomas (OR:1.05, p = 0.63) and serrated polyps (RR:1.03, p = 0.63) were also not significantly inversely associated with Vit-D supplementation. Our study shows that Vit-D does not seem to have a role in the chemoprevention of colorectal neoplasms. However, additional well-designed studies are needed in order to draw safe conclusions. A potentially beneficial role of Vit-D supplementation in CRC primary prevention in individuals with severe vitamin D deficiency as well in the primary prevention of early-onset CRC, requires further investigation.