Associations of dietary intakes of anthocyanins and berry fruits with risk of type 2 diabetes mellitus: a systematic review and meta-analysis of prospective cohort studies.

To investigate the associations of dietary intakes of anthocyanins and berry fruits with type 2 diabetes mellitus (T2DM) risk and to evaluate the potential dose-response relationships based on prospective cohort studies. Cochrane library, Embase and PubMed databases were systematically searched up to Jan 2016 for relevant original studies. Summary relative risks (RRs) were calculated with a random effects model comparing the highest with lowest category. Dose-response was estimated using restricted cubic spline regression models. Three cohort studies reporting dietary anthocyanin intake with 200 894 participants and 12 611 T2DM incident cases, and five cohort studies reporting berry intake with 194 019 participants and 13 013 T2DM incident cases were investigated. Dietary anthocyanin consumption was associated with a 15% reduction of T2DM risk (summary RR=0.85; 95% confidence interval (CI): 0.80-0.91; I2=14.5%). Consumption of berries was associated with an 18% reduction of T2DM risk (summary RR=0.82, 95% CI: 0.76-0.89; I2=48.6%). Significant curvilinear associations were found between dietary intake of anthocyanins (P for nonlinearity=0.006) and berries (P for nonlinearity=0.028) and T2DM risk, respectively. The risk of T2DM was decreased by 5%, with a 7.5 mg/day increment of dietary anthocyanin intake (RR=0.95; 95% CI: 0.93-0.98; I2=0.00%) or with a 17 g/day increment of berry intake (RR=0.95, 95% CI: 0.91-0.99; I2=0.00%), respectively. Higher dietary intakes of anthocyanins and berry fruits are associated with a lower T2DM risk.