Purpose: to examine the relationship between circulating vitamin D level and 
risk of breast cancer.
Methods: This case-control study was conducted in the surgical oncology 
departments at Assiut University's South Egypt Cancer Institute from September 
1
st, 2019 to May 31st, 2020. The study enrolled 140 people (70 cases with newly 
diagnosed breast cancer and 70 age-matched controls from hospital visitors).
The researcher obtained informed consent from the study participants. The 
questionnaire included inquiries about the following aspects: serum vitamin D 
level; data pertinent to demographic and clinical characteristics; parity; 
menstrual and contraceptive histories; dietary history; sun exposure; BMI; and 
waist-to-hip ratio were collected by face-to-face interview and compared 
between the two groups. Regarding the breast cancer cases, pathologic 
characteristics were evaluated against the vitamin D level.
Results: The mean age of breast cancer cases was 51.54 vs. 50.11±5.44 years in 
the control group. Remarkable proportions of breast cancer cases and controls 
were found to have a low serum level of vitamin D. The study revealed that 
94.3% of cases have vitamin D levels less than 20 ng/mL versus 78.6% in the 
control group. The odds ratio of breast cancer associated with a vitamin D level 
20 ng/ml was more than 5 times higher with levels 20 ng/ml after adjustment for 
age, BMI, sun exposure, family income, education status, and family history of 
breast cancer.
Conclusion: Because vitamin D levels were found to be associated with the risk 
of breast cancer in the current study, every effort should be made to improve 
women's health and socioeconomic status, particularly in less privileged 
communities such as rural upper Egypt.