Cornmilk protein powder can be used to measure overall protein oxidation in human studies and in animal studies.The role of protein (amino acid) oxidation in the whole body protein status and whole body protein metabolism is not known. The oxidation of proteins might be a factor to maintain an adequate protein balance to serve optimal protein synthesis. This test can provide a relative indication of the whole body capacity to oxidize proteins. As a substrate, we use natural enriched milk proteins (corn milk proteins) and after oral intake of a test dose of 30 g we measure the 13CO2 output in breath . The details of this method have been published and the method has been validated. (Reckman et al., 2016; Reckman et al., 2018)
Applications
We analysed the rate of oxidation of whey proteins and observed that this oxidation rate was faster that the oxidation of glucose (Reckman et al., 2016). Preliminary studies indicate that in healthy males, protein oxidation is unaffected after a protein restricted diet , but clear differences in respons to restriction could be observed, which could not be related to the measured parameters (Reckman et al., 2018).Preliminary studies were performed to analyse the maximal oxidation capacity. It was observed that this capacity was in the same range as dietary protein intake (ca 1.4 g/kg body weight/day.) It is not known if this capacity of milk protein oxidation varies between individuals.
These data suggest that the oxidation process could be biologically relevant.
Physical exercise above a certain threshold leads to an increase in protein oxidation rate.(Reckman et al. , to be published)
A clear knowledge cap exists about the regulatory factors of protein oxidation.
Reckman GAR, Koehorst M, Priebe M, Schierbeek H, Vonk RJ. 13C Protein Oxidation in Breath: Is It Relevant for the Whole Body Protein Status? J Biomed Science Engineer 2016;9:160-169
Reckman GAR, Navis GJ, Krijnen WP, Van der Schans CP, Vonk RJ, Jager Wittenaar H. Whole Body Protein Oxidation Unaffected after a Protein Restricted Diet in Healthy Young Males. Nutrients 2019;11(1):E115