A Review of the Hypoglycemic Effects of Five Commonly Used Herbal Food Supplements

Hyperglycemia is a pathological condition associated with prediabetes and diabetes. The incidence of prediabetes and diabetes is increasing and imposes great burden on healthcare worldwide. Patients with prediabetes and diabetes have significantly increased risk for cardiovascular diseases and other complications. Currently, management of hyperglycemia includes pharmacological interventions, physical exercise, and change of life style and diet. Food supplements have increasingly become attractive alternatives to prevent or treat hyperglycemia, especially for subjects with mild hyperglycemia. This review summarized current patents and patent applications with relevant literature on five commonly used food supplements with claims of hypoglycemic effects, including emblica officinalis (gooseberry), fenugreek, green tea, momordica charantia (bitter melon) and cinnamon. The data from human clinical studies did not support a recommendation for all five supplements to manage hyperglycemia. Fenugreek and composite supplements containing emblica officinalis showed the most consistency in lowering fasting blood sugar (FBS) or glycated hemoglobin (HbA1c) levels in diabetic patients. The hypoglycemic effects of cinnamon and momordica charantia were demonstrated in most of the trials with some exceptions. However, green tea exhibited limited benefits in reducing FBS or HbA1c levels and should not be recommended for managing hyperglycemia. Certain limitations are noticed in a considerable number of clinical studies including small sample size, poor experimental design and considerable variations in participant population, preparation format, daily dose, and treatment duration. Future studies with more defined participants, standardized preparation and dose, and improved trial design and size are warranted.