Protein and Amino Acids in Human Nutrition

Proteins are essential components in all cells and in the diet. Protein–energy malnutrition represents the dominating nutritional problem in the world. Proteins comprise various amounts of 20 amino acids, 9 of these are essential. The biological functions are related to the protein structure and may be lost when denaturalized. Dietary protein has a twofold role, a specific as source of amino acids for protein synthesis and a nonspecific as energy-yielding macronutrient, which makes protein turnover closely related to energy metabolism. Nitrogen analyses are used for indirect determination of protein and protein balance. However, studies on protein needs and turnover call for advanced metabolic energy balance studies.