Vitamin D and liver cancer risk: A meta-analysis of prospective studies.

BACKGROUND AND OBJECTIVES:The association between circulating vitamin D and liver cancer risk has been controversial on the basis of epidemiological studies. The aim of this study was to quantitatively evaluate this association with prospective studies. METHODS AND STUDY DESIGN:A systematic literature search was implemented in PubMed and Scopus databases up to June 2019. Using a random-effects model, the multivariate-adjusted relative risks (RRs) with corresponding 95% confidence interval (CI) were pooled for the highest versus lowest category. Trend estimation was conducted with a two-stage dose-response meta-analysis. RESULTS:Six independent prospective studies (992 liver cancer events and 60,811 participants) were included for data synthesis. The summary estimate showed that a higher circulating vitamin D was associated with lower risk of liver cancer (Summary RR=0.78; 95% CI: 0.63, 0.95; I2=53.6%, p=0.035). Dose-response analysis indicated that liver cancer was associated with 8% (95% CI: 0.89, 0.95) lower risk with a 10 nmol/L increment of circulating vitamin D concentration. CONCLUSIONS:The present study provides substantial evidence that a higher concentration of circulating vitamin D would have conferred protection against liver cancer.