Long-term ingestion of a fermented soybean-derived Touchi-extract with α-glucosidase inhibitory activity is safe and effective in humans with borderline and mild type-2 diabetes

Water-extracted Touchi, a traditional Chinese food, exerts a strong inhibitory activity against rat intestinal alpha-glucosidase in foodstuffs, and Touchi-extract (TE) has been shown to have an antihyperglycemic effect in rats and humans after a single oral administration. In the present complementary study, the effects of powdered Houji-tea with or without (placebo) TE, a formula designed to enhance good compliance, were monitored in a 3-mo double-blind randomized group comparison study with placebo controls in humans with borderline and mild type-2 diabetes (n = 36). All subjects ingested Houji-tea with or without 0.3 g of TE before each of three meals per day for 3 mo. In the TE group, initial fasting blood glucose (6.9 +/- 0.1 mmol/L) and glycated hemoglobin (HbA(1c); 6.1 +/- 0.1 %) levels gradually decreased; fasting blood glucose decreased significantly after 3 mo (6.4 +/- 0.3 mmol/L; P < 0.05) as did HbA(1c) (5.6 <plus/minus> 0.2%; P < 0.01) levels at 2 mo postingestion of TE and thereafter. In contrast, fasting blood glucose and HbA(1c) levels did not change in the placebo group. In this study, other biochemical variables were not affected in any of the subjects, and no one complained of any side effects or abdominal distension. Moreover, there was no deterioration as assessed by fasting blood glucose and HbA(1c) levels after withdrawal of TE ingestion. Thus, the alpha-glucosidase inhibitory TE demonstrated an antihyperglycemic effect and may prove useful for improving glycemic control in subjects suffering from borderline and type-2 diabetes mellitus.