Can amino acid requirements for nutritional maintenance in adult humans be approximated from the amino acid composition of body mixed proteins?

The quantitative needs for the dietary indispensable amino acids in adult human protein nutrition are still poorly established. Tracer studies with 13C-labeled amino acids have been undertaken previously in our laboratories to reevaluate and further determine the minimum physiological needs for selected indispensable amino acids in healthy adult volunteers. For those amino acids that have not yet been studied by this approach we have proposed a tentative set of requirement figures based on considerations of the amino acid composition of body mixed proteins and the rate of obligatory amino acid losses (i.e., losses when the diet contains no proteins or amino acids). Here we provide an argument for, and a justification of, this approach as an interim measure until more comprehensive data become available on the quantitative aspects of amino acid metabolism in healthy humans.