Protein intake and requirements with reference to diet and health

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Abstract
We have reviewed, in brief, various aspects of human protein and amino-acid metabolism with particular reference to the assessment of protein and amino acid needs. The current requirements for protein and amino acids in various groups of healthy people were then summarized. Emerging from this discussion was the view that some plant protein foods, such as soy for example, are of much better nutritional value for humans than has been commonly appreciated. The figures for requirements were then compared with intakes characteristic of populations in the developed regions of the world. It is evident that these intakes greatly exceed the minimum physiologic need for most healthy individuals but little is known about the possible health benefit or otherwise of these intake levels of protein. Furthermore, also it was pointed out that consideration of different food proteins in relation to amino acid and nitrogen requirements constitutes an important, but only an initial, basis for evaluating the role of dietary protein and of various food protein sources in human nutrition and health. Different food protein sources influence, in various ways, the utilization of and possibly requirements for other nutrients. This complicates determination of requirements and the setting of rational and safe dietary allowances as well as of dietary guidelines for individuals and population groups. A further assessment of the role and impact of food proteins and their interrelationships with and interactions among other foods and essential nutrients, particularly with respect to the nutritional and metabolic status of free-living individuals and their long-term health, presents a difficult but exciting research challenge to nutrition and other health professionals.