Abstract 4232: Dairy product consumption across the life course and breast cancer risk
Authors: Riseberg Emily , Lam Wai Ching , Wu You , Eliassen A. Heather , Wang Molin , Zhang Xuehong , Smith-Warner Stephanie , Willett Walter C. 
Published: April 2023

Abstract
Previous literature on dairy products and risk of breast cancer is inconsistent, and the relationship may depend on the life period of the dietary assessment and menopausal status. We aimed to prospectively investigate dairy product consumption during adolescence, pre-menopause, post-menopause, and lifetime in relation to risk of breast cancer overall and by tumor subtypes. We analyzed data from 59,655 women in the Nurses’ Health Study (NHS) collected from 1980 to 2016. Average intake of dairy products during adulthood was assessed by validated semi-quantitative food frequency questionnaires (FFQ) assessed every 2 to 4 years throughout follow-up. Participants reported recalled adolescent dietary intake in 1986. Premenopausal intake was calculated as the cumulative average intake from the 1980 FFQ to the last FFQ completed prior to premenopausal breast cancer diagnosis or menopause. Postmenopausal intake was calculated as the intake from the first FFQ after menopause to postmenopausal breast cancer diagnosis or end of follow-up. Lifetime intake was calculated as the average of adolescent, premenopausal, and postmenopausal intake. Cox proportional hazards models were used to estimate hazard ratios (HRs) relating dairy product consumption to breast cancer risk overall and by subtype. Models were adjusted for age, race, height, body mass index, alcohol intake, energy intake, and other breast cancer risk factors and lifestyle factors. We documented 5,549 incident cases of invasive breast cancer during 30 years of follow-up (N=5,128 postmenopausal). Adolescent total dairy intake was modestly associated with higher breast cancer risk (HR for a 1 serving/d increment=1.03; 95% confidence interval [CI]=1.00, 1.07). Similar results were found for adolescent milk intake (HR=1.04; 95% CI=1.02, 1.08). In contrast, adolescent cheese intake was associated with a lower risk of breast cancer (HR=0.83; 95% CI=0.70, 0.98). All three associations were more apparent for postmenopausal compared to premenopausal breast cancer. For lifetime intake, only the association with cheese intake was maintained (HR=0.83; 95% CI=0.73, 0.93). Observed inverse associations between lifetime and adolescent cheese intake and breast cancer appeared stronger among estrogen receptor negative and luminal B (adolescent only) subtypes. These findings suggest that adolescent and lifetime cheese intake may be associated with reduced risk of breast cancer and adolescent milk intake may be associated with increased risk.
Citation Format: Emily Riseberg, Wai Ching Lam, You Wu, A. Heather Eliassen, Molin Wang, Xuehong Zhang, Stephanie Smith-Warner, Walter C. Willett. Dairy product consumption across the life course and breast cancer risk. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4232.