Soy and the risk of type 2 diabetes mellitus: A systematic review and meta-analysis of observational studies.

BACKGROUND: Increasing studies have focused on the relationship between soy intake and type 2 diabetes mellitus risk, but the results are inconsistent. We conduct a meta-analysis to evaluate the relationship.

METHODS: The databases of PubMed, Web of Science and Embase were searched up to Dec 2016. A random-effect model was used to pool the results of included studies.

RESULTS: Eight studies with 19 reports met the inclusion criteria. A significant inverse association was shown between soy intake and type 2 diabetes mellitus risk with an overall RR of 0.77 (95% CI = 0.66-0.91) with high heterogeneity. Besides, there was an obvious relationship between soy protein and isoflavones intake and risk of T2DM with the summary RR was 0.88 (95% CI = 0.80-0.97) with no heterogeneity. In the subgroup analysis, a statistically significant protective effect of soy consumption was observed in women (RR = 0.65; 95% CI = 0.49-0.87), cross-sectional studies (RR = 0.45; 95% CI = 0.30-0.67), and Asian populations (RR = 0.73; 95% CI = 0.61-0.88).

CONCLUSIONS: Soy products and soy constituents (soy protein and soy isoflavones) may be associated with a lower risk of type 2 diabetes mellitus. Future studies should focus on the dose-response effect and the mechanism.