Whey or Casein Hydrolysate with Carbohydrate for Metabolism and Performance in Cycling

Abstract

The protein type most suitable for ingestion during endurance exercise is undefined. This study compared co-ingestion of either 15 g/h whey or casein hydrolysate with 63 g/h fructose: maltodextrin (0.8:1) on exogenous carbohydrate oxidation, exercise metabolism and performance. 2 h postprandial, 8 male cyclists ingested either: carbohydrate-only, carbohydrate-whey hydrolysate, carbohydrate-casein hydrolysate or placebo-water in a crossover, double-blind design during 2 h of exercise at 60%W max followed by a 16-km time trial. Data were evaluated by magnitude-based inferential statistics. Exogenous carbohydrate oxidation, measured from (13)CO2 breath enrichment, was not substantially influenced by co-ingestion of either protein hydrolysate. However, only co-ingestion of carbohydrate-casein hydrolysate substantially decreased (98% very likely decrease) total carbohydrate oxidation (mean±SD, 242±44; 258±47; 277±33 g for carbohydrate-casein, carbohydrate-whey and carbohydrate-only, respectively) and substantially increased (93% likely increase) total fat oxidation (92±14; 83±27; 73±19 g) compared with carbohydrate-only. Furthermore, only carbohydrate-casein hydrolysate ingestion resulted in a faster time trial (-3.6%; 90% CI: ±3.2%) compared with placebo-water (95% likely benefit). However, neither protein hydrolysate enhanced time trial performance when compared with carbohydrate-only. Under the conditions of this study, ingesting carbohydrate-casein, but not carbohydrate-whey hydrolysate, favourably alters metabolism during prolonged moderate-strenuous cycling without substantially altering cycling performance compared with carbohydrate-only.

Comparison of energy supplements during prolonged exercise for maintenance of cardiac function: carbohydrate only versus carbohydrate plus whey or casein hydrolysate

“…The experimental trials were performed 7 days apart using a randomised, double-blind, fourway crossover design as previously described (Oosthuyse et al, 2015). During each trial the cyclists ingested an equal volume of either a non-caloric placebo drink or 1 of 3 experimental beverages of identical carbohydrate content but with differing protein source as follows: D r a f t without additional protein (CHO-only) or with either additional whey hydrolysate (CHOwhey) or casein hydrolysate (CHO-casein).…”

“…During the TT, the cyclists rode on their own bicycles setup on a Tacx i-Magic ergometer (Tacx bv, Wassenaar, Netherlands) that was interfaced with computer software to simulate a 16 km route with an undulating gradient as described previously (Oosthuyse et al 2015). The cyclists drank a 200 mL aliquot of the test beverage immediately before commencing the time trial and a further 200 mL at 8 km during the TT.…”

“…As detailed previously (Oosthuyse et al 2015), all beverages besides the placebo were prepared as a 7% carbohydrate solution and according to the drinking routine already described, provided 63 g of carbohydrate•h -1 and 900 mL•h -1 . The source of carbohydrate consisted of a 0.8:1 ratio of fructose: maltodextrin (Krystar 300 crystalline fructose, Tate and Lyle, Decatur, IL, USA and Glucidex 12, Roquette Frères, Lestrem Cedex, France, respectively).…”

“…Whey protein contains the protein alpha-lactalbumin that has a particularly high content of cysteine (Mariotti et al 2004), and the small peptide fragments of a whey hydrolysate produce greater antioxidant capacity compared to when ingesting intact whey isolate (Liu et al 2014). However, a comparison of the exercise performance and metabolic response to PSE when ingesting carbohydrate plus added whey hydrolysate or carbohydrate plus added casein hydrolysate demonstrated that only carbohydrate-casein hydrolysate ingestion produced a clear improvement in exercise performance compared to placebo-water ingestion in athletes that participated 2 h postprandially (Oosthuyse et al 2015). Furthermore, only the carbohydratecasein hydrolysate altered the metabolic response to PSE such that carbohydrate oxidation was reduced and fat oxidation was increased compared to when carbohydrate-only was ingested (Oosthuyse et al 2015), suggestive of carbohydrate sparing energetic that would be expected to delay the occurrence of an energy deficit.…”

“…However, a comparison of the exercise performance and metabolic response to PSE when ingesting carbohydrate plus added whey hydrolysate or carbohydrate plus added casein hydrolysate demonstrated that only carbohydrate-casein hydrolysate ingestion produced a clear improvement in exercise performance compared to placebo-water ingestion in athletes that participated 2 h postprandially (Oosthuyse et al 2015). Furthermore, only the carbohydratecasein hydrolysate altered the metabolic response to PSE such that carbohydrate oxidation was reduced and fat oxidation was increased compared to when carbohydrate-only was ingested (Oosthuyse et al 2015), suggestive of carbohydrate sparing energetic that would be expected to delay the occurrence of an energy deficit. Casein, which is another milk-derived protein, also contains all of the essential amino acids and has only a marginally lower D r a f t proportion of branched-chain amino acids when compared with whey (Calbet et al 2004).…”