Opuntia ficus-indica ingestion stimulates peripheral disposal of oral glucose before and after exercise in healthy men

The purpose of this study was to investigate the effect of Opuntia ficus-indica (OFI) cladode and fruit-skin extract on blood glucose and plasma insulin increments due to high-dose carbohydrate ingestion, before and after exercise. Healthy, physically active men (n = 6; 21.0 ± 1.6 years, 78.1 ± 6.0 kg) participated in a double-blind placebo-controlled crossover study involving 2 experimental sessions. In each session, the subjects successively underwent an oral glucose tolerance test at rest (OGTTR), a 30-min cycling bout at ~75% VO2max, and another OGTT after exercise (OGTTEX). They received capsules containing either 1,000 mg OFI or placebo (PL) 30 min before and immediately after the OGTTR. Blood samples were collected before (t0) and at 30-min intervals after ingestion of 75 g glucose for determination of blood glucose and serum insulin. In OGTTEX an additional 75-g oral glucose bolus was administered at t60. In OGTTR, OFI administration reduced the area under the glucose curve (AUCGLUC) by 26%, mainly due to lower blood glucose levels at t30 and t60 (p < .05). Furthermore, a higher serum insulin concentration was noted after OFI intake at baseline and at t30 (p < .05). In OGTTEX, blood glucose at t60 was ~10% lower in OFI than in PL, which resulted in a decreased AUCGLUC (-37%, p < .05). However, insulin values and AUCINS were not different between OFI and PL. In conclusion, the current study shows that OFI extract can increase plasma insulin and thereby facilitate the clearance of an oral glucose load from the circulation at rest and after endurance exercise in healthy men.