Effect of whey supplementation on blood markers of protein metabolism in young and elderly after resistance exercise

Abstract Introduction: Ingestion of whey protein has been shown to be superior to casein in the acute stimulation of anabolic responses in muscle. The composition of whey protein may alter how rapidly the amino acids are available after consumption, and thus affect acute anabolic responses in muscle and other tissues. Aims: To investigate how ingestion of different whey products, influences the acute changes in the blood amino acid and urea concentration following standardized resistance exercise. Subjects and methods: Twenty two young (20-35 years) and 14 elderly (>70 years), both men and women, were included in this double-blinded placebo controlled (partial) crossover study. The whey group went through the trial twice, one with native whey and one with WPC-80, while the milk group functioned as the control group. The study was designed as an acute exercise trial with a pre workout baseline measurement and post workout measurement for 5 h, and recovery measurement at 24 h. Blood concentrations of amino acids, glucose, insulin and urea was used to investigate the differences in the acute response after ingestion of native whey, WPC-80 and milk. Results: Ingestion of native whey in the young resulted in a higher concentration of plasma leucine compared to WPC-80 and milk between 45 and 220 min post workout (p<0.05), and a greater area under the curve (AUC) for leucine and BCAA compared to WPC-80 (p<0.05). The same results were found for the elderly between 60 and 220 min post workout (p<0.05) and for AUC for leucine (p<0.05). At 45 min post workout, ingestion of native whey and WPC-80 resulted in a higher plasma leucine concentration for young compared to elderly. Ingestion of native whey resulted in a higher percentage increase in urea at 180 and 300 min post workout compared to milk, for the young (p<0.01) and the elderly (p<0.01). Conclusion: Ingestion of native whey resulted in a more rapid and greater plasma leucine concentration, compared to WPC-80 and milk, which most likely was attributed to the higher leucine content in native whey, and a faster digestion and absorption kinetics for native whey, compared to milk. Another finding was the significant difference in amino acid uptake between young and elderly. The young experienced a rapid increase in plasma leucine concentration, while the elderly experienced a slower, more sustained response after ingestion of native whey. The higher percentage increase in urea found after ingestion of native whey versus milk, can be attributed to higher BCAA content and the greater aminoacidemia seen after ingestion of native whey.