title: Role of vitamin D deficiency and lack of sun exposure in the incidence of premenopausal breast cancer: a case control study in Sabzevar, Iran.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Toxicology and Pharmacology, Faculty of Pharmacy, Islamic Azad University, Pharmaceutical Sciences Branch (IAUPS), Tehran, Iran E-mail : sepideharbabi@yaho.com.
authors.forename: Sepideh Arbabi
authors.initials: SA
authors.lastname: Bidgoli
authors.forename: Hamid
authors.initials: H
authors.lastname: Azarshab
mesh_terms: D000328:Adult; D001943:Breast Neoplasms / Q000453:epidemiology*; D016022:Case-Control Studies; D004531:Eggs / Q000706:statistics & numerical data; D004781:Environmental Exposure / Q000706:statistics & numerical data*; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D015994:Incidence; D007492:Iran / Q000453:epidemiology; D008019:Life Style; D017697:Premenopause; D065840:Protective Factors; D012307:Risk Factors; D012424:Rural Population; D013472:Sunlight; D014808:Vitamin D Deficiency / Q000453:epidemiology*