Potential effects of Alliaceae and Brassicaceae edible plants on blood glucose levels in patients with type 2 diabetes: A systematic review and meta-analysis of clinical trials

Type 2 diabetes (T2D) is one of the main leading causes of mortality worldwide, and its global prevalence will increase within the next years. Many pre-clinical studies demonstrated the potential effects of edible plants from Alliaceae and Brassicaceae on the regulation of blood glucose levels. Of note, secondary metabolites from Alliaceae and Brassicaceae share the ability to slowly release hydrogen sulfide (H2S), which is emerging as a crucial modulator of the "glucose-insulin system". However, the results of clinical studies evaluating the effects of such edible plants on glycaemic control in patients with T2D are quite conflicting. We performed a systematic review and meta-analysis of controlled clinical trials, both parallel and cross-over, searching four databases (Pubmed, Embase, Scopus and the Cochrane library). Only English-written papers evaluating the effects of Alliaceae and Brassicaceae on glycaemic parameters in diabetic patients have been included. 16 studies met the inclusion criteria, and 12 were included in the random-effects meta-analysis. Consumption of Alliaceae or Brassicaceae significantly reduced fasting blood glucose (FBG) levels compared with the placebo group (mean reduction: -12.67 mg/dl [95% confidence interval (CI) - 19.66; - 5.68]). Moreover, Alliaceae and Brassicaceae significantly improved the effects of standard antidiabetic therapy (mean reduction in FBG levels in patients receiving combination therapy compared with patients only receiving standard antidiabetic therapy: -6.75 mg/dl [-12.62; -0.88]). Overall, the regular consumption of these edible plants was safe and well-tolerated. We suggest that edible plants containing organosulfur compounds are endowed with promising nutraceutical potential in the treatment of T2D.