Mulberry leaves and water chestnut tea reduces postprandial blood glucose in borderline diabetic Japanese: A randomized, double-blind, placebo-controlled crossover study.

Abstract

Background and objectives: Postprandial hyperglycemia is a risk factor not only for diabetes mellitus, but also arteriosclerosis. Therefore, controlling the rapid postprandial increase in blood glucose levels is necessary. This study aimed to develop a mulberry leaf and water chestnut husk tea and investigate its effect on postprandial blood glucose levels.

Methods and study design: We measured the polyphenols and 1-deoxynojirimycin contents as well as antioxidant activity of mulberry leaf and water chestnut husk tea in an in vitro experiment. The effect of the tea on postprandial blood glucose levels in 30 participants with borderline diabetes was investigated in a randomized, double-blind, placebo-controlled crossover comparison study.

Results: The 1-deoxynojirimycin and total polyphenol contents in the tea (test food, 3g) were 10.2±0.8 and 61.3±1.4 mg, respectively. The test food showed higher antioxidant activity than the placebo food. Compared with those in the placebo group, blood glucose levels in the test group significantly decreased 30 and 60 min after eating rice. Additionally, insulin was significantly lower at all time points (30, 60, 90, and 120 min after rice consumption).

Conclusions: The mulberry leaves and water chestnut mix tea may be an effective beverage to reduce insulin secretion and prevent rapid increases in blood glucose levels in patients with borderline diabetes.