A new concept to establish protein requirements.

Abstract

There is an increased need to establish the protein requirements for body weight maintenance and optimal health in humans. Different methods were developed in the past to assess protein requirements in which known amounts of protein/amino acids were provided. The purpose of this paper is to propose a new concept of establishing protein requirements in healthy and diseased conditions using a novel stable isotope approach. In the past years, we consistently found that when using a novel stable isotope pulse approach the intracellular production of amino acids (i.e., phenylalanine and tyrosine) is more than double the plasma rate of appearance, as measured by the commonly used primed constant infusion approach, leading to a net protein breakdown that is more than twice than estimated in the past. Net protein breakdown in the fasted state may provide a good estimation of the actual net protein loss that would take place during the day and thus can be used to estimate daily protein requirements. Our recent study found that a net protein breakdown ∼1 g protein/kg body weight/day was equal to the habitual protein intake, suggesting that there is a relation between habitual protein intake and protein requirements. As net protein breakdown is lower with advanced aging and in patient populations with comorbidities, a lower protein requirement for body weight maintenance is suggested. We propose a new concept to establish actual protein requirements of healthy and disease conditions, using a pulse tracer administration and to consider individual habitual protein intake and health conditions.