Milk protein oxidation in healthy subjects: A preliminary study

The role of protein oxidation in the regulation of whole body protein metabolism is unknown. Previously, it was observed that vigorous exercise led to increased protein oxidation. To further characterise 13C-milk protein oxidation in healthy subjects, the oxidation of ingested 13C-protein after an overnight fast was measured using a non-invasive 13C-protein breath test. This approach enables the analysis of 13C-protein oxidation kinetics and the effect of interfering factors. It was found that the estimated maximal 13C-milk protein oxidation was 0.07 g min−1, corresponding to a theoretical maximal oxidation capacity of ≈1.4 g kg body weight−1 d−1. No indications were found for preferential oxidation of non-essential amino acids. Combined ingestion of 30 g 13C-whey protein with 30 g glucose resulted in a 19% decrease of 13C-whey protein oxidation. It was concluded that exogenous 13C-whey protein oxidation can be affected by other co-ingested nutrients like glucose.