WHEY PROTEIN AND CARBOHYDRATES PRODUCE "BETTER" BLOOD FACTORS BUT DO NOT TRANSLATE INTO OBVIOUS PERFORMANCE IMPROVEMENTS
Morifuji, M., Aoyama, T., Nakata, A., Sambongi, C., Koga, J., Kurihara, K., Kanegae, M., Suzuki, K., & Higuchi, M. (2009). Effect of co-ingestion of carbohydrate and whey protein hydrolysates on exercise performance and blood biochemical parameters of carbohydrate metabolism in male athletes. A paper presented at the 14th Annual Congress of the European College of Sport Science, Oslo, Norway, June 24-27.
This study compared the effect of the co-ingestion of carbohydrate and whey protein hydrolysates with carbohydrate-alone on exercise performance and post-exercise blood biochemical parameters of carbohydrate metabolism in male athletes (N = 8). Ss exercised on a cycle ergometer continuously for 60 minutes on two separate occasions at 68% VO2max, interrupted by six two-minute intervals at 88% VO2max. Ss cycled at 60% VO2max during the last 10 minutes. On one occasion, immediately after and 30, 60, 90, and 120 minutes after exercise, Ss received a supplement containing 1) 17.5 g carbohydrate, 2) 3.0 g whey protein hydrolysates and 17.5 g carbohydrate (L-WPH), or 3) 8.0 g whey protein hydrolysates and 17.5 g carbohydrate (H-WPH). On both occasions, after a two-hour recovery, a time-trial was performed. Blood samples were drawn before exercise and at 0, 30, 60, 90 and 120 minutes after the exercise, and also after the time-trial test.
The blood glucose response was lower and the plasma insulin response was significantly higher in the H-WPH group compared to the carbohydrate-alone group. The concentrations of plasma amino acid and dipeptide were also higher in both whey protein hydrolysates groups compared to the carbohydrate group. There was a strong positive correlation between the plasma concentrations of insulin and the biochemical markers of Leu, Ile, Met, Thr, Tyr, Phe, Trp, Ile-Leu and Val-Leu. Furthermore, the plasma IL-6 and free-fatty acid levels after the time-trial were significantly lower in the H-WPH group than in the carbohydrate group. The time-trial endurance performance was not statistically different between the treatments.
Implication. The co-ingestion of carbohydrate and whey protein hydrolysates was more effective than ingestion of carbohydrate alone for stimulating insulin secretion and plasma amino acid and dipeptide availability in exercise-trained athletes. Furthermore, blood parameters of substrate metabolism, such as free-fatty acids and IL-6 also changed after co-ingestion of carbohydrate and whey protein hydrolysates. The ingestion of carbohydrate with whey protein hydrolysates has a beneficial role of increasing post-exercise glycogen repletion rates but does not translate into any obvious performance improvements. [This is another instance of where significant biochemical/physiological changes occur but are not accompanied by significant performance alterations. It is dangerous to infer that theoretical physiology, of which this is an example, has a direct correlate with performance improvement.]
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