I have indirect calorimetry (IC) data pre- and every 2 hours -post consumption of a mixed meal in healthy young men. Upon arrival to the laboratory, following a >12h overnight fast, a urine sample was collected and measured. All post-meal urine was collected, total volume measured and urea concentrations calculated, to enable for protein metabolism (g/min) corrections to the subsequent IC data (derived from Frayn, 1983). However, since the urine sample in the fasted state is a single time-point measure, and I don't know when they previously urinated, I have no time element to calculate the contribution of protein metabolism for the pre-meal IC data.
Thus, does anyone know of any reference values/percentages/correction factors/ relevant papers for fasted protein metabolism contribution in healthy young males?
Use references presented in this book: modern nutrition in health and diseases.
I am glad that you are actually thinking about this problem. Too many folks assume that protein oxidation is zero, for simplicity. The correct way to do this is to constantly collect urine within the renal pelvis. Otherwise, It is quite reasonable to assume that the protein oxidized within 24h is equal to the protein ingested (minus feces) in 24h.
Unfortunately, there are many more variables in this methodology. The amino acid pool excess [what is not being utilized during the anabolic cycle during sleep] that will be excreted in urine depends on: the amount of protein consumed the day before, the quantity of protein fully digested, how much gets adsorbed; the amount of weight bearing done during the day, plus, I am sure, more variables
I think that you should divide each single time-point measure data with each urine creatinine concentration to corrct the pre-meal IC data, if you don't know when they previously urinated.
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