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Vitamin D intake, blood vitamin D levels, and the risk of breast cancer: a dose-response meta-analysis of observational studies

Song D1,2, Deng Y1,2, Liu K3, Zhou L1,2, Li N1,2, Zheng Y2, Hao Q2, Yang S2, Wu Y2, Zhai Z2, Li H4, Dai Z1,2.

Aging (Albany NY). 2019 Dec 28;11(24):12708-12732. doi: 10.18632/aging.102597. Epub 2019 Dec 28.

 

Epidemiological studies have indicated that blood vitamin D levels are linked to cancer. Here we conducted a dose-response meta-analysis based on published observational studies to evaluate the association of vitamin D intake and blood vitamin D levels with breast cancer susceptibility. PubMed, EMBASE, and Web of Science databases were searched up to January 2019. The pooled odds ratio (OR) and 95% confidence intervals (CIs) were extracted to estimate the risk. We identified 70 relevant studies on blood vitamin D levels (50 studies) and vitamin D intake (20 studies), respectively. Linear and nonlinear trend analyses were performed and showed that an increase in blood vitamin D levels by 5 nmol/l was associated with a 6% decrease in breast cancer risk (OR = 0.94, 95% CI = 0.93-0.96). Similar results were obtained for premenopausal (OR = 0.96, 95% CI = 0.93-0.99) and postmenopausal women (OR = 0.96, 95% CI = 0.94-0.98). The pooled OR of breast cancer risk for a 400IU/day increase in vitamin D intake was 0.97 (95% CI = 0.92-1.02).

In conclusion, we found that breast cancer risk was inversely related to blood vitamin D levels; however, no significant association was observed in vitamin D intake.