Dietary polyphenols and risk of breast cancer in a predominantly low-income population: a prospective analysis in the Southern Community Cohort Study (SCCS).

BACKGROUND: Few studies have examined the associations of specific dietary polyphenols with breast cancer (BC) risks or among non-Hispanic Black (NHB) female individuals in the United States.

OBJECTIVES: We aim to evaluate the associations between total and subclasses of polyphenol intake and BC risk, stratified by body mass index (BMI), estrogen receptor (ER)/progesterone receptor (PR) status, menopausal status, and racial and ethnic subgroups.

METHODS: The study included 42,260 female participants from the Southern Community Cohort Study, a large prospective cohort of predominantly low-income NHB Americans. The dietary polyphenol components were assessed using a validated culturally sensitive 89-item food frequency questionnaire designed specifically for nutrient intakes in the South. Cox proportional hazards model was used to assess the associations after adjustment for confounders including sociodemographic and lifestyle factors.

RESULTS: Intakes of total polyphenols were higher in non-Hispanic white (1122 ± 727 mg/d) than in NHB female individuals (535±349 mg/d). Intakes of total polyphenol, particularly phenolic acids, were associated with reduced risk of BC incidence among female individuals with the ER+ and PR+ BC type comparing the highest to the lowest quintile [hazard ratio (HR) 0.69; 95% confidence interval (CI): 0.51, 0.94; P-trend = 0.003; HR 0.70; 95% CI: 0.53, 0.95; P-trend = 0.005, respectively]. Phenolic acid was inversely related to BC among postmenopausal female individuals (HR 0.76; 95% CI: 0.59, 0.97; P-trend = 0.02) and female individuals with a BMI ≥ 25 kg/m2 (HR 0.77; 95% CI: 0.60, 0.98; P-trend = 0.01) comparing the highest to the lowest quintile. Intakes of tyrosols were associated with increased risk of BC among NHB female individuals (HR 1.34; 95% CI: 1.03, 1.73; P-trend = 0.01) and female individuals with a BMI ≥ 25 kg/m2 (HR 1.31; 95% CI: 1.04, 1.65; P-trend = 0.004).

CONCLUSIONS: In this predominantly low-income United States population, intakes of total polyphenol and phenolic acids were associated with reduced risk of BC among those with ER+ and PR+ BC type, postmenopausal, and female individuals with overweight/obesity.