Herbs and herbal preparations for glycemic control in diabetes mellitus (a systematic review)

To conduct an updated systematic review of the published literature to fined effective antihyperglycemic herbs and herbal preparations used in clinical trials for improving glycemic control in type 2 diabetes mellitus. We performed an electronic literature search of Medline, Science direct, Scopus, ProQuest, Ebsco, Googlescholar, and Cochrane Library Database, from January 2002 to June 2010. The key outcome for antidiabetic effect was changes in one or more parameters including FBG, PPG, and HbA1(c), as well as improve in insulin sensitivity or insulin resistance. Total clinical trials retrieved were 222, of which 38 were randomized controlled trial (RCT), examined single herbs or combination of herbs as potential therapy for type 2 diabetes mellitus. Of these 38 trials, the direction of the evidence for glycemic control was positive in 26 trials (68.4%). Several herbal medicine used in clinical trials had beneficial effects on glycemic control, but there is still insufficient evidence to draw definitive conclusion about the efficacy of herbs and herbal preparations for treatments of diabetic patients. Among the RCT studies, the good evidence in glycemic control was found in Citrullus colocynthus, Ipomoea betatas, and Silybum marianum although the sample size was low.