Abstract
Vitamin D has been suggested as one of the critical factors for female reproductive health with protective activities against different cancers but there are conflicting facts regarding its role on breast cancer without any clear data on premenopausal cases. This study aimed to evaluate the role of vitamin D from dietary sources and sunlight exposure on the incidence of premenopausal breast cancer. We conducted a case control study on 60 newly diagnosed premenopausal breast cancer patients and 116 normal women who lived in Sabzevar and surrounding villages in Razavi, Khorasan, a rural and conservative area of Iran. The mean concentrations of 25-OH vitamin D in cases and controls were 15.2 ± 8.15 vs 15.5 ± 7/45 ng/ml, both well below normal values elsewhere. In fact 50% of analyzed individuals showed very severe or severe vitamin D deficiency and the rest (25%) were detected in suboptimal levels. Although the lack of vitamin D 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 of sunlight exposure because the breast cancer patients had total body coverage from sun (p=0.007, OR=10.131, CI 98% 0.314-78.102). This study pointed out the role of vitamin D and other possible risk factors on the development and growth of breast tumors in this special geographical region. Although this study has revealed the interactions between hormonal and environmental factors in this province of Iran, understanding the deficiency pattern and its contribution to other lifestyle factors elsewhere is also necessary.
Highlights
Vitamin D is one of the critical factors for female reproductive health which may have protective activities against many cancer types, including breast cancer
This study aimed to evaluate the role of vitamin D from dietary sources and sunlight exposure on the incidence of premenopausal breast cancer
In Iran, Breast cancer (BC) is ranked as the most prevalent malignancy among women and its probability increases with the age in general (Harirchi et al, 2011) but we showed recently that premenopausal breast cancer may have different feature and etiology in Iran by occurring one decade earlier than their counterparts in other countries and as a result of hormonal and environmental interactions especially by higher exposure to endocrine disrupting chemicals (EDCs) and AhR expression (Bidgoli et al, 2010; 2011)
Summary
Vitamin D is one of the critical factors for female reproductive health which may have protective activities against many cancer types, including breast cancer. Vitamin D has been suggested as one of the critical factors for female reproductive health with protective activities against different cancers but there are conflicting facts regarding its role on breast cancer without any clear data on premenopausal cases. The questionnaire covered the possible skin reaction to sunlight exposure, time and frequency spent outdoors in the sun and personal protection against with special emphasis to dressing style. Questions relating to sunlight exposure included the following: residence (city, village); outdoor activities in the sun and the aver-age hours per day spent in the sun during the summer and the other 3 seasons, usual (usual was defined as >50% of the time) sun protection during the summer and the other 3 sea-sons, trips to summer climate locations during the winter and the frequency
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