Role of Vitamin D Deficiency and Lack of Sun Exposure in the Incidence of Premenopausal Breast Cancer: a Case Control Study in Sabzevar, Iran

Background: Vitamin D has been suggested as one of the critical factors for female reproductive health withprotective activities against different cancers but there are conflicting facts regarding its role on breast cancerwithout any clear data on premenopausal cases. This study aimed to evaluate the role of vitamin D from dietarysources and sunlight exposure on the incidence of premenopausal breast cancer. Materials and
Methods: Weconducted a case control study on 60 newly diagnosed premenopausal breast cancer patients and 116 normalwomen who lived in Sabzevar and surrounding villages in Razavi, Khorasan, a rural and conservative area ofIran.
Results: The mean concentrations of 25-OH vitamin D in cases and controls were 15.2±8.15 vs 15.5±7/45ng/ml, both well below normal values elsewhere. In fact 50% of analyzed individuals showed very severe orsevere vitamin D deficiency and the rest (25%) were detected in suboptimal levels. Although the lack of vitaminD and calcium supplementation increased slightly the risk of premenopausal breast cancer (p=0.009, OR=1.115,CI 95%=1.049-1.187), higher prevalence of weekly egg consumption (86.66% vs 96.55%, p=0.023, OR=0.232,CI 95% 0.065-0.806) showed a slight protective role. The last but the most important risk factor was lack ofsunlight exposure because the breast cancer patients had total body coverage from sun (p=0.007, OR=10.131,CI 98% 0.314-78.102).
Conclusion: This study pointed out the role of vitamin D and other possible risk factorson the development and growth of breast tumors in this special geographical region. Although this study hasrevealed the interactions between hormonal and environmental factors in this province of Iran, understandingthe deficiency pattern and its contribution to other lifestyle factors elsewhere is also necessary.