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.