Nutrition and protein turnover in man

ABSTRACT

The composition and homoeostasis of the body are maintained by the integrated action of all the tissues and organs. Therefore, although it is of interest to look at the component parts separately, each part has to be fitted functionally into a greater over-all framework. Whole-body protein turnover represents the integration of one fundamental activity of living organisms. Each individual protein has its own turnover rate, responding in a particular way to any change in metabolism. The turnover in the whole body is the resultant of these activities and in this sense has been likened to basal metabolic rate. The measurement of protein turnover in man has wide application, not only to the normal metabolic changes taking place during growth but also to disorders of metabolism in many clinical conditions. Although the standard nitrogen balance technique gives valuable information on net changes, it cannot indicate either the intensity of nitrogen metabolism or the mechanism by which changes are brought about. Nitrogen balance is the resultant of differences between synthesis and breakdown, which may change in the same or opposite directions in any given clinical state.(AU)