The book of diet / by Chalmers Watson.

  • Watson, Chalmers.
Date:
[1913]
Catalogue details

Licence: In copyright

Credit: The book of diet / by Chalmers Watson. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

    22/456 (page 18)
    medium for taking the food elements to the tissues, and (2) as a solvent for the waste products of the tissues which are excreted in solution by the kidneys (see p. 272). NUTRITIVE VALUE OF FOODS. A word may be said as to the methods of determining the nutritive value of foods. This is done :— 1. By a study of its chemical composition. 2. By ascertaining its heat value. 3. By reference to its physiological properties—the ease with which it is digested and absorbed. Chemical Composition of Food.—Chemical analysis of a food tells us the proportion of protein, fat, carbohydrates, salts, and water present in its composition. The results of chemical analysis, therefore, give us some information as to the value of food, both as a tissue builder and as a source of energy or heat production. The Heat Value of a Food. Physical and Physiological Heat Values.—The heat value of different foods may be determined experimentally by the use of an instrument known as the Bomb calorimeter, a special form of heat chamber, the result being expressed in calories. The standard of heat production is the calorie, which means the amount of heat required to raise the temperature of I kilogram of water i° centigrade. The amount of heat evolved by the combustion in a calorimeter of i gram of the different food-stuffs is as follows :— I gram protein produces 4 calories. I ,, carbohydrate produces 4 calories. I ,, fat produces 8.9 calories. These figures represent the amount of energy set free by