Effects of medicinal food plants on impaired glucose tolerance: A systematic review of randomized controlled trials

Background: The objective of this systematic review was to assess available scientific data on the efficacy and safety of medicinal food plants for the treatment of impaired glucose tolerance. Methods: We included randomized controlled trials (RCTs) with a minimum follow-up period of 6 weeks. The diagnosis was determined by fasting plasma glucose values after twohour oral glucose tolerance testing (OGTT). Two authors independently extracted data and evaluated bias. The Cochrane tool of risk of Bias Tool was used. Results: This review included ten trials. Most studies were highly biased as data were incomplete or reporting was selective. The two-hour fasting plasma glucose after the curcumin extract intervention showed statistical significance after 3, 6 and 9 months: p < 0.01. Also, glycosylated haemoglobin levels A1c (HbA1c) values after curcumin extract intervention showed statistical significance after 3, 6 and 9 months: p < 0.01. Insulin resistance (HOMA-IR) after curcumin extract intervention showed statistical significance after 6 months and after 9 months: p < 0.05 and p < 0.01. Conclusions: Curcumin has shown the confident results to be effective for the treatment of impaired glucose tolerance. Fenugreek and flaxseed may also be effective, but due to low quality of these studies the results must be interpreted with caution. (C) 2017 Elsevier B.V. All rights reserved.