Flavonoids intake and risk of type 2 diabetes mellitus: A meta-analysis of prospective cohort studies

Epidemiological studies exploring the role of flavonoids intake in preventing type 2 diabetes mellitus (T2DM) showed inconsistent results. Therefore, we performed a meta-analysis of relevant studies to examine the relationship between flavonoids intake and risk of T2DM. We hypothesized that flavonoids intake may decrease the risk of developing T2DM.A systematical search in PubMed and Embase until September 2017 was performed to identify eligible prospective cohort studies. The summary relative risks (RRs) and 95% confidence intervals (CIs) were calculated using random-effect models. Dose-response pattern between total flavonoids intake and T2DM risk was also estimated.Eight prospective studies were included with 312,015 participants, of whom 19,953 developed T2DM during the follow-up periods of 4 to 28 years. Compared with lower consumption, high intake of total flavonoids was associated with a decreased risk of T2DM (RR: 0.89, 95% CI: 0.82-0.96). Among flavonoid subclasses, inverse correlations with T2DM were achieved for intakes of anthocyanidins, flavan-3-ols, flavonols, and isoflavones. Dose-response meta-analysis indicated a curvilinear relationship between total flavonoids intake and incident T2DM (P for nonlinearity = .042), with a significant risk reduction at an intake of 550mg/day. When assuming a linear pattern, the risk of T2DM was decreased by 5% for each 300-mg/day increment in total flavonoids intake (RR: 0.95, 95% CI: 0.93-0.97).Our study suggests that higher intakes of total flavonoids and subclasses (anthocyanidins, flavan-3-ols, flavonols, and isoflavones) are associated with lower risk of T2DM.