The Association Between Vitamin D Supplementation and Reduced Risk of Breast and Endometrial Cancer: A Meta-Analysis

This review and meta-analysis assessed the relationship between vitamin D levels and the risk of breast and endometrial cancers, and the efficacy of vitamin D supplementation as a preventive strategy. We searched PubMed and the Cochrane Library using “vitamin D” and “breast and endometrial cancer,” focusing on human studies in English. Ten high-quality studies were selected based on robust design and data integrity. We analyzed effect sizes—odds ratios, risk ratios, and hazard ratios with 95% confidence intervals—using a random-effects model. Our findings suggest that higher vitamin D levels are linked to a lower risk of these cancers, especially in premenopausal women and those with greater sun exposure. Although some studies found no significant links, the overall evidence supports vitamin D's protective potential. Further randomized trials are necessary to confirm these results and define vitamin D deficiency standards in cancer risk assessment.