Effects of dairy products, calcium and vitamin D on ovarian cancer risk: a meta-analysis of twenty-nine epidemiological studies

Abstract

The findings for the roles of dairy products, calcium, and vitamin D on ovarian cancer risk remain controversial. We aimed to assess these associations by using an updated meta-analysis. Five electronic databases (e.g., PubMed and Embase) were searched from inception to December 24, 2019. Pooled relative risks (RRs) with 95% confidence intervals (CIs) were calculated. A total of 29 case–control or cohort studies were included. For comparisons of the highest vs. lowest intakes, higher whole milk intake was associated with increased ovarian cancer risk (RR: 1.35, 95% CI: 1.15, 1.59), whereas decreased risks were observed for higher intakes of low-fat milk (RR: 0.84, 95% CI: 0.73, 0.96), dietary calcium (RR: 0.71, 95% CI: 0.60, 0.84), and dietary vitamin D (RR: 0.80, 95% CI: 0.67, 0.95). Additionally, for every 100-g/d increment, increased ovarian cancer risks were found for total dairy products (RR: 1.03, 95% CI: 1.01, 1.04) and for whole milk (RR: 1.07, 95% CI: 1.03, 1.11); however, decreased risks were found for a 100-g/d increased intakes of low-fat milk (RR: 0.95, 95% CI: 0.91, 0.99), cheese (RR: 0.87, 95% CI: 0.76, 0.98), dietary calcium (RR: 0.96, 95% CI: 0.95, 0.98), total calcium (RR: 0.98, 95% CI: 0.97, 0.99), dietary vitamin D (RR: 0.92, 95% CI: 0.87, 0.97), and increased levels of circulating vitamin D (RR: 0.84, 95% CI: 0.72, 0.97). These results show that whole milk intake might contribute to a higher ovarian cancer risk, whereas low-fat milk, dietary calcium, and dietary vitamin D might reduce the risk.