A Blend of Phellodendron and Crape Myrtle Extract Improves Acute Glucose Tolerance in Healthy Men

Abstract

BACKGROUND: Several plant-based ingredients have been shown to regulate glucose tolerance. PURPOSE: To investigate the acute effects of a nutritional supplement containing a proprietary blend of Phellodendron and Crape Myrtle extract on serum glucose and insulin in response to an oral glucose tolerance test (OGTT). METHODS: Using a randomized, double-blind, cross-over design, 10 healthy, exercise-trained men reported to the lab in a 10 hr fasted state, on two different mornings, separated by 1-2 weeks. On both days, subjects ingested a 75 gram dextrose solution. Fifteen minutes prior to the OGTT subjects ingested either the supplement (Phellodendron and Crape Myrtle extract) or a placebo. Blood samples were collected before ingestion of the supplement or placebo and at 15, 30, 45, 60, and 75 min post OGTT. Samples were analyzed for serum glucose and insulin. A 2 (condition) × 6 (time) ANOVA was performed, and area under the curve (AUC) was calculated. RESULTS: In relation to glucose, while no interaction effect was noted (p=0.69), a condition effect was noted (p=0.01), with values lower for supplement compared to placebo. A time effect was also noted (p<0.0001), with values at the 15 and 30 min collection times higher than pre-ingestion (p<0.05). AUC was not different (p=0.23), although a 9.9% reduction was noted with the supplement (534±69mg·dL-1·75min-1) compared to placebo (593±133mg·dL-1·75min-1). In relation to insulin, a trend for a condition effect was noted (p=0.06), with values lower for supplement compared to placebo. A time effect was also noted (p<0.0001), with values at 15, 30, 45, and 60 min higher than pre-ingestion (p<0.05). No interaction (p=0.95) or AUC effect (p=0.29) was noted, although a 33.3% reduction in AUC was noted with the supplement (117±13μIU·mL-1·75min-1) compared to placebo (156±33μIU·mL-1·75min-1). CONCLUSION: Acute ingestion of a nutritional supplement containing a blend of Phellodendron and Crape Myrtle extract can lower the serum glucose response to an OGTT. These data are specific to a small sample of healthy, exercise-trained, non-diabetic men. Further work pertaining to this nutritional supplement is warranted using a larger sample of subjects, in particular those with impaired glucose tolerance, who ingest the supplement chronically as opposed to acutely.