Fruit and vegetable consumption and the risk of type 2 diabetes: A systematic review and dose-response meta-analysis of prospective studies

Abstract

Background: The high prevalence of type 2 diabetes has a considerable impact on global health. Several modifiable risk factors for type 2 diabetes have been established, such as dietary factors. The association between intake of fruit and vegetables and their subtypes, and the risk of type 2 diabetes has been investigated in several studies, but the results have not been consistent. Objective: The aim of this master’s thesis is to conduct a systematic review and dose- response meta-analysis of prospective studies on the association between intake of fruit and vegetables and risk of type 2 diabetes, with particular focus on identifying specific types of fruits and vegetables that may be beneficial, and to clarify the strength and shape of the dose- response relationship. Design: PubMed and Embase databases were searched up to 26th of June 2018. Prospective cohort studies of fruit and vegetable consumption and type 2 diabetes mellitus were included. Summary relative risks and 95% confidence intervals were estimated using a random effects model. Results: Our results indicated an inverse association between intake of fruits, and fruit and vegetables combined and the risk of type 2 diabetes. No significant associations were found for intake of vegetables. Of subtypes of fruit and vegetables, especially apples, blueberries, grapefruit and grapes and raisins were strongly associated with a reduced risk, while cabbage, cauliflower, kale, mustard and chard greens and potatoes were strongly associated with an increased risk of type 2 diabetes. Conclusions: This meta-analysis suggests that there is a weak inverse association between fruit and vegetable intake and type 2 diabetes risk. There is some indication of both inverse and positive associations between intake of several fruit and vegetables subtypes and type 2 diabetes risk, however, because of the limited number of studies, further studies are needed before firm conclusions can be made.