Postprandial amino acid availability after intake of intact or hydrolyzed meat protein in a mixed meal in healthy elderly subjects: a randomized, single blind crossover trial

The absorption of dietary proteins affects the anabolic response, among others protein synthesis. For elderly, optimal amino acid absorption is warranted to preserve the amino acid pool of the body, especially skeletal muscle proteins. Therefore, the aim of this study was to characterize if hydrolyzing meat protein (HMP) would improve the amino acid absorption after ingestion of meat compared to equal amounts of the same meat proteins but present in a different structure; steak or minced meat. With a crossover study design on 12 healthy older adults (> 65 years of age, BMI 18.5–30), the amino acid absorption kinetics were explored by ingesting 0.55 g protein/kg LBM as a mixed meal together with intrinsically [2H5]phenylalanine labeled meat proteins prepared as a STEAK, MINCED meat, or HMP. Plasma [2H5]phenylalanine enrichment as well as AA concentrations were measured by mass spectrometry from blood samples drawn during a 5-h postprandial period. After HMP ingestion, [2H5]phenylalanine was faster absorbed in the initial 2 h compared to STEAK and MINCED. The peak time in AA concentrations was faster in HMP compared to STEAK and MINCED. However, the peak AA concentrations were not different between STEAK, MINCED, and HMP. Although HMP showed to have the fastest initial amino acid appearance in older adults, the peak EAA concentrations were similar after ingesting meal with either STEAK, MINCED, or HMP in the 5-h postprandial period.