Dietary carbohydrate intake is associated with a lower risk of breast cancer: A meta-analysis of cohort studies

The association between dietary carbohydrate intake and breast cancer (BC) remains controversial. This meta-analysis aimed to elucidate the association between dietary carbohydrate intake (dietary fiber, whole grain, sugar, and unidentified carbohydrate) and BC risk in a cohort study. We hypothesized that dietary carbohydrate intake is associated with an increased risk of BC. PubMed, Cochrane Library, Web of Science, Embase, and Chinese databases were searched for relevant articles through March 2021. Pooled relative risks (RRs) were calculated using random-effects model. The results showed the pooled RRs for dietary carbohydrate intake and BC incidence, mortality, and recurrence were 0.98 (95% confidence interval [CI], 0.95-1.00), 0.96 (95% CI, 0.89-1.03), and 0.96 (95% CI, 0.83-1.11), respectively. In subgroup analysis, a negative association was found between dietary fiber and BC incidence and mortality. Pooled RRs were 0.94 (95% CI, 0.91-0.98) and 0.88 (95% CI, 0.78-1.00). Dose-response analysis showed that every 10-g/d increments in dietary fiber intake was associated with a significant 3% reduction in BC incidence, and every 10-g/d increase in dietary fiber intake, BC incidence in premenopausal women was significantly reduced by 14%. In addition, the marginal relation for whole grain, which may decrease BC incidence (RR = 0.95; 95% CI, 0.86-1.05), but increase BC mortality (RR = 1.02; 95% CI, 0.92-1.14). A marginal positive relation was also observed between sugar and BC incidence (RR = 1.04; 95% CI, 0.94-1.14). This meta-analysis of cohort studies suggested that dietary carbohydrate intake is associated with a lower risk of BC incidence, mortality, and recurrence.