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