Fruit and vegetable intake and risk of type 2 diabetes mellitus: meta-analysis of prospective cohort studies

Objective: To clarify and quantify the potential dose-response association between the intake of fruit and vegetables and risk of type 2 diabetes. Design: Meta-analysis and systematic review of prospective cohort studies. Data source: Studies published before February 2014 identified through electronic searches using PubMed and Embase. Eligibility criteria for selecting studies: Prospective cohort studies with relative risks and 95% CIs for type 2 diabetes according to the intake of fruit, vegetables, or fruit and vegetables. Results: A total of 10 articles including 13 comparisons with 24 013 cases of type 2 diabetes and 434 342 participants were included in the meta-analysis. Evidence of curve linear associations was seen between fruit and green leafy vegetables consumption and risk of type 2 diabetes (p=0.059 and p=0.036 for non-linearity, respectively). The summary relative risk of type 2 diabetes for an increase of 1 serving fruit consumed/day was 0.93 (95% CI 0.88 to 0.99) without heterogeneity among studies (p=0.477, I-2=0%). For vegetables, the combined relative risk of type 2 diabetes for an increase of 1 serving consumed/day was 0.90 (95% CI 0.80 to 1.01) with moderate heterogeneity among studies (p=0.002, I-2=66.5%). For green leafy vegetables, the summary relative risk of type 2 diabetes for an increase of 0.2 serving consumed/day was 0.87 (95% CI 0.81 to 0.93) without heterogeneity among studies (p=0.496, I-2=0%). The combined estimates showed no significant benefits of increasing the consumption of fruit and vegetables combined. Conclusions: Higher fruit or green leafy vegetables intake is associated with a significantly reduced risk of type 2 diabetes.