A matched case–control study of bean intake and breast cancer risk in urbanized Nigerian women

Purpose Bean intake has been associated with reduced risk of breast cancer, however; only a few studies considered molecular subtypes status and none in African women living in Sub-Saharan Africa (SSA). Therefore, the purpose of this study was to examine the associations between dietary intake of beans and breast cancer including its subtypes in Nigerian women. Methods Overall, 472 newly diagnosed patients with primary invasive breast cancer were age-matched (± 5 years) with 472 controls from the Nigerian Integrative Epidemiology of Breast Cancer (NIBBLE) Study from 01/2014 to 07/2016. We collected the dietary intake of beans using a food frequency questionnaire (FFQ). Beans_alone intake was categorized into three levels never (never in the past year), low (≤ 1 portion/week), and high intake (> 1 portion/week). We used conditional and unconditional logistic regression models to estimate the Odds Ratio (OR) and 95% Confidence Intervals (CI) of beans_alone intake and the risk of breast cancer and by its molecular subtypes, respectively. Results The mean (SD) age of cases was 44.4(10.0) and of controls was 43.5(9.5) years. In the case group, more than half (51.1%) have never consumed beans_alone in the past year compared to 39.0% in the control group. The multivariable models showed inverse associations between beans_alone (high vs. none) and breast cancer (OR = 0.55; 95%CI: 0.36–0.86, p-trend = 0.03), triple-negative (OR = 0.51 95%CI: 0.28–0.95, p-trend = 0.02) and marginally associated with hormone receptor-positive (OR = 0.53, 95%CI: 0.29–0.96, p-trend = 0.06). Conclusion Dietary intake of beans_alone may play a significant role in reducing the incidence of breast cancer, particularly of the more aggressive molecular subtype, triple-negative, in African women living in SSA