The production of intrinsically labeled milk protein provides a functional tool for human nutrition research

Abstract

Oral or intravenous administration of labeled, free amino acids does not allow the direct assessment of protein digestion and absorption kinetics following dietary protein intake. Consequently, dietary protein sources with labeled amino acids incorporated within the protein are required. The aim of this study was to produce milk proteins intrinsically labeled with l-[1-(13)C]phenylalanine that would allow the assessment of protein digestion and absorption kinetics and the subsequent muscle protein synthetic response to dietary protein intake in vivo in humans. Two Holstein cows (body weight of 726 +/- 38 kg) were continuously infused with l-[1-(13)C]phenylalanine at 402 micromol/min for 44 t..