Vitamin D exposure and risk of breast cancer : a meta-analysis

Abstract

Background: The relationship between vitamin D and breast cancer is still controversial. The present meta-analysis examines the effects of the 25(OH)D, 1.25(OH)D and vitamin D intake on breast cancer risk. Methods: A PubMed-database search was conducted to include all papers published with the keywords ‘‘BREAST CANCER” AND “VITAMIN D” with at least one reported relative risk (RR) or odds ratio (OR). In total fifty-eight studies published between 1998 and 2016 has been analyzed. Information about type of study, hormonal receptors and menopausal status was retrieved. A pooled OR or RR has been estimated by weighting individual OR/RR by the inverse of their variance. Results: Our study showed a protective effect between 25 (OH) D and breast cancer (OR=0.66, IC: 0.57-0.76) in case-control studies, although no association was observed when restricting the analysis to nested case-control studies (RR=0.91, IC: 0.82-1.01). However, a subgroup analysis on premenopausal women showed a consistent protective association in both case-control studies (0.68, IC: 0.53-0.87) and nested case-control studies (0.67, IC: 0.49-0.92). No significant association was found for vitamin D intake or 1.25(OH) D. Conclusion: This systematic review suggests a protective relationship between vitamin D (measured as 25(OH) D) and breast cancer development in premenopausal women.