Carbohydrate (CHO) foods taken prior to, and while exercising, enhance long-lasting (> 1 hour) performance by sustaining blood glucose levels. However, it is unclear which amount, type and form of CHO increases endurance.
The current study investigated the effects of a natural food product such as raisins in comparison with commercial sport chews. The CHO supplement effects, on the metabolism, gastrointestinal (GI) tolerance and endurance performance, were tested in 11 male runners.
AdvertisementEach runner went through 3 cycles of being randomly assigned to either intake raisins (31g), chews (Clif bar, 3 pieces) or water only. At the end of each cycle, the runners participated in an 80min treadmill run and a 5-km time trial (TT). GI indicators were noted, perceived exertion (RPE) recorded and a blood sample taken at 20min intervals.
Other parameters monitored every 20-min included oxygen consumption (VO2), heart rate (HR), respiratory exchange ratio (RER), blood lactic acid, serum free fatty acids (FFA), glycerol, insulin, plasma glucose, electrolytes, creatine kinase and GI indications.
The study results show no differences between the groups with regards to VO2, HR, electrolytes, lactic acid, glycerol and RPE. The mean plasma glucose and RER, during the 80min run, were considerably higher with chews as compared with water alone. However, serum FFA was higher with water only as opposed to raisins and chews. Serum insulin was highest in the chews group than in the raisins and water groups. Plasma creatine kinase, for the second half of the 80 min run, was highest with raisins. The TT was faster in both the carbohydrate groups, as compared with water alone, while GI trouble was mild for all treatments.
Thus, raisins and chews equally increased running ability with no noteworthy differences in GI condition.
Reference: Natural versus Commercial Carbohydrate Supplementation and Endurance Running Performance; Brandon Too et al; BMC Journal of the International Society of Sports Nutrition 2012