A randomized controlled study of dose-finding, efficacy, and safety of mulberry leaves on glycemic profiles in obese persons with borderline diabetes

Mulberry (Morus alba L.) leaves have been used in traditional medicine for treating hyperglycemia. However, there remains difficulties in the implementation of mulberry leaves in evidence-based practice. The aims of this study were to examine the optimal dose of 1-deoxynojirimycin (DNJ) in mulberry leaves and to determine the efficacy and safety of mulberry leaves in glycemic control in obese persons with borderline diabetes.First, healthy adults were recruited into the dose-finding study and randomly allocated to ingest sucrose solution concurrently with mulberry leaf powder at weights equivalent to 0 (control), 6, 12, and 18 mg of DNJ. Postprandial glucose and undesirable effects were evaluated. Second, obese persons with borderline diabetes were randomly assigned into the mulberry-leaves treatment group (12 mg of mulberry DNJ three times daily) and the control group in the 12-week prospective study. Blood glucose and insulin as well as adverse effects were determined.Twelve mg of mulberry DNJ was the minimum effective dose attenuating postprandial hyperglycemia. Mulberry leaves decreased fasting plasma glucose (FPG) by 3.86 ± 5.99 mg/dL (p = 0.002) and glycated hemoglobin (HbA1c) by 0.11 ± 0.22 % (p = 0.011) when compared with the baseline levels. Improvement in glucose tolerance was not observed. Furthermore, mulberry leaves tended to ameliorate insulin resistance (p = 0.057). Adverse events of mulberry leaves commonly found in this study were gastrointestinal symptoms including bloating, flatulence, and loose stools.Mulberry leaves possessed favorable effects on glycemic profiles without serious side effects.