Research Paper|Volume 11, Issue 24|pp 12708—12732

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

Dingli Song^1,², Yujiao Deng^1,², Kang Liu³, Linghui Zhou^1,², Na Li^1,², Yi Zheng², Qian Hao², Si Yang², Ying Wu², Zhen Zhai², Hongtao Li⁴, Zhijun Dai^1,²

¹Department of Breast Surgery, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China
²Department of Oncology, The Second Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
³Department of Hepatobiliary Surgery, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
⁴Department of Breast, Head and Neck Surgery, The 3rd Affiliated Teaching Hospital of Xinjiang Medical University (Affiliated Tumor Hospital), Urumqi, China

* Equal contribution

Received: October 3, 2019Accepted: December 2, 2019Published: December 28, 2019

https://doi.org/10.18632/aging.102597

Copyright © 2019 Song et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY 3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Abstract

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.