Legume and Nuts Consumption in Relation to Odds of Breast Cancer: A Case-Control Study

Abstract

Previous studies on the association between legume and nuts intake and risk of breast cancer have mainly been focused on individual components of legume or nuts, rather than consumption of the whole food group. This study aimed to investigate the relation between legume and nuts intake in relation to breast cancer in Iranian women. In this population-based case-control study, we enrolled 350 pathologically confirmed new cases of breast cancer and 700 controls which were matched with cases in terms of age and socioeconomic status. Dietary intakes were assessed using a validated block-format 168-item semi-quantitative food frequency questionnaire. Legume intake was computed by summing up the consumption of lentils, peas, chickpeas, and different kinds of beans, including red beans and pinto beans. To calculate nuts consumption, we summed up intake of mixed nuts, almond, peanut, walnut and hazelnut. Data on potential confounding variables were also collected using pre-tested questionnaires. Mean consumption of legume and nuts among cases and controls were 14.7 ± 15.0 and 2.3 ± 5.6, respectively. A significant inverse association was found between legume intake and breast cancer (OR: 0.41, 95% CI: 0.30–0.57); such that after adjusting for confounders, participants in the top tertile of legume intake had 46% lower odds of breast cancer compared with those in the bottom tertile (OR: 0.54, 95% CI: 0.36–0.88). Such inverse association was seen among postmenopausal women (OR: 0.51, 95% CI: 0.31–0.85) and also among normal-weight participants (OR: 0.49, 95% CI: 0.29–0.82). In terms of nuts intake, it was inversely associated with odds of breast cancer (OR: 0.16, 95% CI: 0.11–0.23). This association remained significant even after taking potential confounders into account (OR: 0.15, 95% CI: 0.09–0.26). The same association was also seen in premenopausal women (OR: 0.21, 95% CI: 0.14–0.31), postmenopausal women (OR: 0.23, 95% CI: 0.13–0.42), normal-weight (OR: 0.15, 95% CI: 0.08–0.28), and overweight or obese people (OR: 0.27, 95% CI: 0.10–0.71). Our findings on the inverse association of legume and nuts intake with odds of breast cancer support the current recommendations on these foods. Prospective studies are needed to further examine this link.