The Possibility of Suppression of Increased Postprandial Blood Glucose Levels by Gamma-Polyglutamic Acid-Rich Natto in the Early Phase after Eating: A Randomized Crossover Pilot Study.

The natto containing high levels of gamma-polyglutamic acid (γ-PGA) was recently developed. We investigated the effect of γ-PGA-rich natto consumption on postprandial glycemic excursion in humans. A randomized crossover meal test study was performed on healthy volunteers aged 20-64 years using the following test meals: (1) white rice (WR), (2) low-γ-PGA natto meal (WR + low-γ-PGA natto), and (3) high-γ-PGA natto meal (WR + high-γ-PGA natto). Blood samples were obtained at each visit before and for 120 min after loading. The incremental area under the curve (IAUC) of blood glucose and insulin levels was calculated and compared among the test meals. The blood glucose's IAUC at 0-120 min, the primary endpoint, was 20.1% and 15.4% lower for the high- and low-γ-PGA natto meal than for the WR, with a significant difference only between the high-γ-PGA natto meal and WR (p < 0.05). The blood glucose's IAUC at 0-15, 0-30, and 0-45 min was lower for the high-γ-PGA natto meal than for the low-γ-PGA natto meal (all p < 0.05). The possibility that high-γ-PGA natto might suppress blood glucose elevations in the early phase after eating is indicated.

Olive leaf tea is beneficial for lipid metabolism in adults with prediabetes: an exploratory randomized controlled trial.

Olive leaves are rich in oleuropein, which has been shown to have beneficial effects on dyslipidemia, type 2 diabetes, and obesity. However, we previously found no significant health benefits of olive leaf tea (OLT) on nonobese and nondiabetic individuals. Thus, we performed this study to further explore the health benefits of OLT in individuals with prediabetes and compare the health benefits between low-concentration OLT (LOLT) and OLT. We hypothesized that OLT will have a more pronounced effect on abdominal obesity as well as glucose and lipid metabolism in prediabetic individuals. Individuals between 40 and 70 years of age with a body mass index of 23.0-29.9 kg/m2 and prediabetes status were recruited and randomly assigned to the OLT or the LOLT group. The intervention, which was the consumption of 330 mL of the test beverage 3 times daily during mealtime, lasted for 12 weeks. After the intervention, serum levels of log-transformed triglycerides (P < .05) and low-density lipoprotein cholesterol (P < .01) decreased significantly in the OLT group (n = 28), with the reductions higher in the OLT group than those in the LOLT group (n = 29, log-transformed triglycerides: P = .079, low-density lipoprotein cholesterol: P < .05). Whereas body weight, waist circumference, and insulin levels were not significantly changed in both groups, fasting plasma glucose levels in the OLT group were significantly decreased compared to those in the LOLT group (P < .05). In conclusion, although the effect of OLT on abdominal obesity and glucose metabolism remains unclear, OLT has been found to have lipid-lowering effects.