Nutrition in everyday practice.

Date:
1939
Catalogue details

Licence: In copyright

Credit: Nutrition in everyday practice. Source: Wellcome Collection.

    11/100 (page 5)
    PROTEIN REQUIREMENTS IN NORMAL NUTRITION* By Lennox G. Bell Winnipeg, Man. II. The protein requirement in the normal diet is a subject upon which a wide difference of opinion exists, and many of the ideas are so much at variance with the known facts that these require¬ ments should be emphasized in any discussion of normal nutrition. In prescribing normal diets the relative proportions of fat and carbohydrate may be varied within wide limits so long as the total caloric requirements are met. In the case of protein, how¬ ever, the optimum requirements cannot be supplied so simply. Protein plays a fundamental role in the body. Primarily, it supplies the necessary amino-acids for growth and repair of tissues, and for the manufacture of certain secretions, antigens, hormones, antibodies, enzymes, etc. In the second place, protein may be used to furnish energy through its deamination and transformation to carbohydrate. A third and perhaps less important function of protein is concerned with the transport of fats and other lipoids in the body. Proteins are nitrogenous compounds formed of a number of amino-acids which combine in several different ways to form a wide variety of proteins, both animal and vegetable. Some twenty- two amino-acids occur in varying amounts in animal and vegetable proteins. It has been established that whereas certain simple amino-acids like glycine and alanine can be synthesized in the body others must be supplied in the diet if normal health and growth are to be maintained. There is experimental evidence to indicate that ten amino-acids cannot be synthesized by the higher vertebrates. Certain proteins such as lactalbumin of milk, beef protein, ovalbumin of eggs, glutenin of wheat, contain all the essential amino-acids, and since in the average mixed diet some or jail these are supplied, only in the case of freak vegetable diets will actual qualitative deficiency arise. The reserve or deposit protein amounts in the adult human pody to approximately 2 kg. Though its fuel value is only 8,000 ralories, about sufficient to maintain life at a basal level for five [lays, nevertheless, with its associated water (10 kg.), it forms a I onsiderable part of the non-skeletal structure of the body. But, *Department of Medicine, University of Manitoba, Winnipeg.