Complementary and alternative medicine for the treatment of type 2 diabetes.

OBJECTIVE: To review clinical evidence supporting complementary and alternative medicine interventions for improving glycemic control in type 2 diabetes mellitus. QUALITY OF EVIDENCE: MEDLINE and EMBASE were searched from January 1966 to August 2008 using the term type 2 diabetes in combination with each of the following terms for specific therapies selected by the authors: cinnamon, fenugreek, gymnema, green tea, fibre, momordica, chromium, and vanadium. Only human clinical trials were selected for review. MAIN MESSAGE: Chromium reduced glycosylated hemoglobin (HbA(1c)) and fasting blood glucose (FBG) levels in a large meta-analysis. Gymnema sylvestre reduced HbA(1c) levels in 2 small open-label trials. Cinnamon improved FBG but its effects on HbA(1c) are unknown. Bitter melon had no effect in 2 small trials. Fibre had no consistent effect on HbA(1c) or FBG in 12 small trials. Green tea reduced FBG levels in 1 of 3 small trials. Fenugreek reduced FBG in 1 of 3 small trials. Vanadium reduced FBG in small, uncontrolled trials. There were no trials evaluating microvascular or macrovascular complications or other clinical end points. CONCLUSION: Chromium, and possibly gymnema, appears to improve glycemic control. Fibre, green tea, and fenugreek have other benefits but there is little evidence that they substantially improve glycemic control. Further research on bitter melon and cinnamon is warranted. There is no complementary and alternative medicine research addressing microvascular or macrovascular clinical outcomes.