Anti-hyperglycemic effect of Vaccinium arctostaphylos in type 2 diabetic patients: a randomized controlled trial.

BACKGROUND Type 2 diabetes mellitus is a common disease. Preliminary data indicate that Vaccinium arctostaphylos L. (Caucasian whortleberry) has a potential effect in glycemic control. Thus, the efficacy and safety of a standardized whortleberry fruit hydroalcoholic extract in the treatment of type 2 diabetic patients were studied. METHODS This randomized double-blind placebo-controlled clinical trial consisted of 37 patients aged 40-60 years with type 2 diabetes who were resistant to conventional oral anti-hyperglycemic drugs. The patients were treated with the whortleberry fruit hydroalcoholic extract (1 capsule = 350 mg, every 8 h for 2 months) in combination with anti-hyperglycemic drugs, and the effects on the blood levels of fasting glucose, 2-hour postprandial glucose, glycosylated hemoglobin (HbA1c), and liver/kidney function were tested, evaluated, and compared with a placebo group (n = 37). RESULTS The extract significantly lowered the blood levels of fasting glucose, 2-h postprandial glucose, and HbA1c (p = 0.007, p <0.001, and p = 0.005, respectively) without any significant effects on the liver/kidney function (p >0.05) compared with placebo at the end. No adverse effects were reported. CONCLUSION Whortleberry may safely improve glycemic control in type 2 diabetic patients.