Protein turnover, ureagenesis and gluconeogenesis.
Level 5 - mechanism / opinion, no new human data
Narrative review of physiological mechanisms without primary empirical data or systematic search
PubMed 22139560 · doi:10.1024/0300-9831/a000064
What was done
This is a narrative review describing the physiological pathways of whole-body protein turnover (synthesis and breakdown), ureagenesis, and gluconeogenesis in humans across states of growth, feeding, and starvation.
What was found
Daily rates of human protein turnover are reported at 300 to 400 g per day compared to typical dietary protein intakes of 50 to 80 g per day. Whole-body protein turnover accounts for approximately 20% of resting metabolic rate in adults (and higher in growing children). Excess amino acids are cleared via oxidation, conversion of amino groups into urea, and conversion of carbon skeletons to glucose via gluconeogenesis.
Why it matters
The review synthesizes the mechanistic links between dietary protein intake, metabolic rate, nitrogen excretion, and glucose homeostasis during varying metabolic states.
Limits
This is a narrative review containing no primary experimental data, sample sizes, search methodology, or confidence intervals for the reported metabolic estimates.
Cited by
- supports The total human body synthesizes about 300 grams of protein daily and recycles approximately 230 grams of amino acids given an intake of 70 grams of protein.