Title : The association of dairy intake and risk of breast cancer: Golestan cohort study
Abstract:
Background: Breast cancer is the most prevalent malignancy among women worldwide. There has been a great attention to relationship of dairy intake and breast cancer risk, up to now. Given the inconsistent findings, this Golestan cohort study was conducted to critically assess the relationship between the consumption of dairy intake years before breast cancer incidence.
Methods: A total of 50,045 healthy participants between 40 and 75 years old participated in this cohort study in 2004–2008 and were followed up to the present. A written informed consent, all the demographic information, a semi-quantitative food frequency questionnaire (FFQ), the anthropometric measurements, and the physical activity questionnaire were filled for all the participants at the beginning of the cohort study. Then, every participant was followed up annually by phone call and the occurrence of any disease, admission to hospital, death and its cause were inquired. Additionally, a medical team collected all the pathology reports and hospital records, and if available, tumor samples were also obtained. The study protocol was approved by the ethical review committee of the Digestive Diseases Research Institute (DDRI), affiliated to Tehran University of Medical Sciences. In this cohort study, patients with breast cancer whose cancer was confirmed during the follow up period on the basis of international classification of diseases and related health problems (ICD10) was assigned to the case group (n=116). The rest of the cohort population were considered as the control group (n = 26,916). A 116-item semi-quantitative food frequency questionnaire (FFQ), which its validity and reliability was previously confirmed, was filled by face to face interview to assess dairy intake. Cox proportional hazards regression model was used to estimate hazard ratio (HR) with 95 % confidence interval of intakes of dairy products for incidence of BC.
Results: At the end of follow-up period, 116 cases of breast cancer were identified and 26,916 participants without history of cancer, acute kidney disorders, fibrosis and cirrhosis were included in the study. Neither all the dairy products did show a significant association with the risk of breast cancer in three models after taking confounders (Model 1: adjusted for Age, Energy intake (Kcal/day): Model 2: adjusted for Age, Energy intake (Kcal/day), Tota Grain, Red Meat, Vegetable, Fruits; Model 3: adjusted for Age, Energy intake (Kcal/day), Tota Grain, Red Meat, Vegetable, Fruits, wealth score, Residence, Ethnicity, Number of Pregnancy, consumption of Opium, Physical activity) in to account. Only Local cheese increased the risk of breast cancer significantly (OR=9.02, 1.03-78.39, Pv=0.04).
Conclusions: Our findings reported that dairy products are not recognized as risk factors for breast cancer in Golestan population. Only high fat unpasteurized cheese which contains high salt and saturated fat significantly increase the risk of breast cancer.
