Improvement of glucose metabolism and safety of acacia bark-derived proanthocyanidins in healthy Japanese adults: A Randomized, Double-blind, Placebo-controlled, Parallel-group Trial

Abstract

Objective: Acacia bark-derived proanthocyanidins exhibit antioxidant, anti-inflammatory, anti-diabetic, hypotensive effects, and improving skin condition, in addition to beneficial effects on blood glucose. Herein, we evaluated the effects of acacia bark-derived proanthocyanidins on fasting and postprandial blood glucose levels in healthy Japanese adults with fasting blood glucose (FBG) levels between 110–125 mg/dL.Methods: Subjects were randomly allocated into 2 groups (n = 33 per group) and consumed 6 tablets/day of either tablets of acacia bark extract containing proanthocyanidins (Acacia group) or placebo for 12 weeks. Evaluation points were at the screening, and after 4-week (4w), 8-week (8w), and 12-week intervention (12w). The primary outcome was FBG level at 12 w, whereas the secondary outcomes were FBG level at 4w and 8w, the FBG changes from Scr to each-week intervention, the percentage of subjects with FBG levels below 110 mg/dL after 12 w, the measured value and the change value from Scr to each-week intervention of HbA1c, the measured value and the change value from Scr to each-week intervention of postprandial blood glucose levels.Results: A total of 33 subjects (18 men, 15 women) from each group were analyzed. The Acacia group had significantly lower FBG levels at 8 and 12 w than the placebo group (P = 0.030 and P = 0.014, respectively). The percentage of subjects with FBG <110 mg/dL at 12 w was marginally higher in the Acacia group than in the placebo group (P = 0.079). HbA1c at 12 w was significantly lowered in the Acacia group compared to the placebo group (P = 0.015).Conclusions: Acacia bark-derived proanthocyanidins were confirmed to have FBG-lowering effects.Trial registration: UMIN000039414Foundation: Acacia-No-Ki Co.,Ltd.Keywords: Acacia bark extract, Proanthocyanidins, Fasting blood glucose level, HbA1c