Vitamin B2 intake reduces the risk for colorectal cancer: a dose-response analysis.

PURPOSE: Several epidemiological studies have assessed the ability of vitamin B2 to prevent colorectal cancer (CRC), but the results are controversial results. We conducted a dose-response meta-analysis to investigate the association between vitamin B2 and CRC risk. METHODS: We searched the PubMed and EMBASE database until January 3, 2018 to identify relevant studies. The pooled relative risks (RRs) with the corresponding 95% confidence intervals (CIs) were calculated using a random-effects model or fixed-effects model. The dose-response relationship was assessed by restricted cubic splines. RESULTS: A total of 14 studies reporting vitamin B2 intake and two studies reporting blood vitamin B2 concentration, comprising 14,934 cases and 1593 cases, respectively, were included in the meta-analysis. Vitamin B2 intake was inversely associated with CRC risk (RR = 0.87; 95% CI 0.81-0.93). Similar results were found for total vitamin B2 intake from diet and supplements (RR = 0.86; 95% CI 0.78-0.94) and dietary vitamin B2 intake (RR = 0.89, 95% CI 0.82-0.98) in subgroup analyses. The dose-response model indicated a non-linear trend, and CRC risk was reduced by 10% when vitamin B2 intake increased to 5 mg/day. In addition, high blood concentrations of vitamin B2 could also reduce the CRC risk (RR = 0.74; 95% CI 0.59-0.92). CONCLUSIONS: This dose-response analysis indicates that vitamin B2 intake is inversely associated with CRC risk. The inverse association may also exist between blood vitamin B2 concentration and CRC risk. These results suggest the importance of vitamin B2 intake in the prevention of CRC.