ABSTRACT
The need for protein in the diet was demonstrated early in the nineteenth century, when it was shown that animals that were fed only on fats, carbohydrates and mineral salts were unable to maintain their body weight, and showed severe wasting of muscle and other tissues. It was known that proteins contain nitrogen (mainly in the amino groups of their constituent amino acids, see §6.4.1), and methods of measuring total amounts of nitrogenous compounds in foods and excreta were soon developed. Figure 10.1 shows an overview of protein metabolism.
