Consumption of whole grains and risk of type 2 diabetes: A comprehensive systematic review and dose-response meta-analysis of prospective cohort studies

Abstract

This study aimed to quantitatively summarize earlier findings on the association between whole grain (WG) intake and type 2 diabetes (T2D) risk. We searched related keywords on PubMed/Medline, Scopus, and Google Scholar up to October 2021. Prospective observational studies investigating the association between WG intake and risk of T2D were included. The random-effects model calculates the summary relative risks by contrasting categories and linear and nonlinear dose-response associations. Eleven prospective cohort studies, including 463,282 participants and 37,249 type 2 diabetes incidents, were analyzed. The pooled relative risk (RR) for the highest versus the lowest WG intake category indicated a 21 decrease in T2D risk (95 confidence interval (CI): 0.73-0.85, I-2 = 77). Each additional 50 grams WG consumption per day was associated with a 23 reduced risk of T2D. The nonlinear association of WG and T2D revealed that 60 grams WG intake per day would give the highest benefit to prevent T2D (Pnonlinearity < 0.001). The findings were not affected by any individual study. No evidence of publication bias was documented. In conclusion, a high intake of WG was associated with a lower risk of T2D. Randomized controlled trials are needed to confirm our results.