Dairy foods, calcium, and risk of breast cancer overall and for subtypes defined by estrogen receptor status: a pooled analysis of 21 cohort studies

• DOI: 10.1093/ajcn/nqab097
• Publication Date: 2021-03-09T12:25:27Z
• Authors: You Wu; Ruyi Huang; Molin Wang; Leslie Bernstein; Traci N Bethea; Chu Chen; Yu Chen; A Heather Eliassen; Neal D Freedman; Mia M Gaudet; Gretchen L Gierach; Graham G Giles; Vittorio Krogh; Susanna C Larsson; Linda M Liao; Marjorie L McCull...; Anthony B Miller; Roger L Milne; Kristine R Monroe; Marian L Neuhouser; Julie R Palmer; Anna Prizment; Peggy Reynolds; Kim Robien; Thomas E Rohan; Sven Sandin; Norie Sawada; Sabina Sieri; Rashmi Sinha; Rachael Z Stolzen...; Shoichiro Tsugane; Piet A van den Br...; Kala Visvanathan; Elisabete Weiderpass; Lynne R Wilkens; Walter C Willett; Alicja Wolk; Anne Zeleniuch-Ja...; Regina G Ziegler; Stephanie A Smith...
• Keywords: MILK CONSUMPTION; Breast Neoplasms; VALIDATION; cheese; CONFIDENCE-INTERVALS; Cohort Studies; yogurt; 03 medical and health sciences; breast cancer; 0302 clinical medicine; Risk Factors; Humans; FREQUENCY QUESTIONNAIRE; VITAMIN-D; METAANALYSIS; 2. Zero hunger; milk; calcium; dairy products; WOMEN; LOGISTIC-REGRESSION; PREVENTION; 3. Good health; DIETARY PATTERNS; Receptors, Estrogen; Multivariate Analysis; Calcium; Female; Dairy Products; pooled analysis; diet

Epidemiologic studies examining the relations between dairy product and calcium intakes and breast cancer have been inconclusive, especially for tumor subtypes.To evaluate the associations between intakes of specific dairy products and calcium and risk of breast cancer overall and for subtypes defined by estrogen receptor (ER) status.We pooled the individual-level data of over 1 million women who were followed for a maximum of 8-20 years across studies. Associations were evaluated for dairy product and calcium intakes and risk of incident invasive breast cancer overall (n = 37,861 cases) and by subtypes defined by ER status. Study-specific multivariable hazard ratios (HRs) were estimated and then combined using random-effects models.Overall, no clear association was observed between the consumption of specific dairy foods, dietary (from foods only) calcium, and total (from foods and supplements) calcium, and risk of overall breast cancer. Although each dairy product showed a null or very weak inverse association with risk of overall breast cancer (P, test for trend >0.05 for all), differences by ER status were suggested for yogurt and cottage/ricotta cheese with associations observed for ER-negative tumors only (pooled HR = 0.90, 95% CI: 0.83, 0.98 comparing ≥60 g/d with <1 g/d of yogurt and 0.85, 95% CI: 0.76, 0.95 comparing ≥25 g/d with <1 g/d of cottage/ricotta cheese). Dietary calcium intake was only weakly associated with breast cancer risk (pooled HR = 0.98, 95% CI: 0.97, 0.99 per 350 mg/d).Our study shows that adult dairy or calcium consumption is unlikely to associate with a higher risk of breast cancer and that higher yogurt and cottage/ricotta cheese intakes were inversely associated with the risk of ER-negative breast cancer, a less hormonally dependent subtype with poor prognosis. Future studies on fermented dairy products, earlier life exposures, ER-negative breast cancer, and different racial/ethnic populations may further elucidate the relation.