Vitamin D supplementation on colorectal cancer incidence and mortality:a meta-analysis of randomized controlled clinical trials and trial sequential analysis

ObjectiveTo evaluate the effect of oral vitamin D supplementation on colorectal cancer incidence and mortality.MethodsAll randomized controlled trials regarding effect of oral vitamin D on colorectal cancer from PubMed, Web of science, Embase and Cochrane Library were searched. Meta analysis and trial sequential analysis of included studies were carried out.ResultsSeven RCTs enrolling 72810 participants were included. Compared with placebo, oral vitamin D supplementation was not associated with the incidence of colorectal cancer(RR=1.1,95%CI:0.93-1.31;p=0.28).Subgroup analysis showed no difference in female participants for incidence of colorectal cancer(RR=1.04,95% CI:0.84-1.28;p=0.73). The pooled RR, included 41643 participants, showed no difference in mortality of colorectal cancer(RR= 0.82, 95% CI:0.56 to 1.21; p = 0.32). Trial sequential analysis showed the z-line did not cross the conventional test boundary, TSA monitoring boundary and futility boundaries.ConclusionOral vitamin D supplementation offers no benefit on the incidence and mortality of colorectal cancer. However, the RCTs with longer follow-up are needed to ascertain the efficacy of Vitamin D, especially among adults with lower serum 25(OH)D levels in future.