Whey protein ingestion has been shown to effectively stimulate postprandial muscle protein accretion in older adults. However, the impact of the amount of whey protein ingested on protein digestion and absorption kinetics, whole-body protein balance, and postprandial muscle protein accretion remains to be established. We aimed to fill this gap by including 33 healthy, older men (73+/-2 y) which were randomly assigned to ingest 10, 20, or 35 g of intrinsically L-[1-(13)C]phenylalanine-labeled whey protein; n=11 per treatment. Ingestion of labeled whey protein was combined with continuous intravenous L-[ring-(2)H(5)]phenylalanine and L-[ring-(2)H(2)]tyrosine infusion to assess the metabolic fate of whey protein-derived amino acids. Dietary protein digestion and absorption rapidly increased following ingestion of 10, 20, and 35 g whey protein, with the lowest and highest (peak) values observed following 10 and 35 g, respectively (P<0.05). Whole-body net protein balance was positive in all groups (19+/-1, 37+/-2, and 58+/-2 mumol*kg(-1)), with the lowest and highest values observed following ingestion of 10 and 35 g, respectively (P<0.05). Postprandial muscle protein accretion, assessed by L-[1-(13)C]phenylalanine incorporation in muscle protein, was higher following ingestion of 35 g when compared with 10 (P<0.01) or 20 g (P<0.05). We conclude that ingestion of 35 g whey protein results in greater amino acid absorption and subsequent stimulation of de novo muscle protein synthesis when compared with the ingestion of 10 or 20 g whey protein in healthy, older men.
|Number of pages||8|
|Journal||American Journal of Physiology : Endocrinology and Metabolism|
|Publication status||Published - Apr 2012|
- fractional synthetic rates
- stable isotopes
- INTRINSICALLY LABELED MILK