Nutrition in everyday practice.

Date:
1939
Catalogue details

Licence: In copyright

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

    10/100 (page 4)
    It is possible to increase efficiency without increasing the calories in a number of other ways. There is, for example, an optimum speed for each occupation, that is, a speed beyond which the energy consumed is out of all proportion to the useful work accomplished. Walking to and from work is an example. Walk¬ ing one mile at the slow rate of 2 miles per hour requires about 60 calories only; whereas, walking at the fast rate of 5 miles per hour, one mile consumes about 600 calories; that is, increasing the speed 23^2 times is so wasteful that the energy expenditure instead of being increased 2J/2 times is increased over ten times. (Calcu¬ lated from data in “Living Machinery”, by A. V. Hill, Harcourt, Brace, 1927). Occupation, diet and income are intimately related. The physician, with his knowledge of food values, may, therefore, be of assistance here also. At its best, the human machine is wasteful; the efficiency of human muscle is approximately 20 per cent only; in the untrained individual it may be appreciably less. Very little can be done about this inherent defect, but much may be done otherwise. A fruit jelly made of gelatine, the juice of one lemon, and a portion of raw fruit has a heat value of about 30 calories only—an amount of energy which a person weighing 150 pounds expends in about one-half hour during sleep. The plebeian bread and butter pudding, made of two slices of bread and butter, one egg, x/i pint of milk and sugar to taste, has a fuel value of 500 to 600 calories—enough to meet about 25 per cent of the total daily expenditure of energy in sedentary occupations. About one-eighth of steak, as purchased, consists of fat. By removing this small percentage of fat, the steak loses about half of its fuel value. The caloric value of one ounce of clear fat pork is equal approximately to two pounds of cabbage, and one ounce of olive oil is equal in energy value to about three pounds of lettuce. Of eighteen different proprietary foods the compositions of which are known to the writer, and the fuel values of which range from 11 to 122 calories per ounce, not one may be purchased for less than eight times, and in one instance over one hundred times, the cost of similar food materials easily prepared at home. Restricted in scope by the limit of space, the object of this article is to outline as briefly as wras thought consistent with clarity some of the more important facts about caloric contents of diets— the different values of food materials; how energy requirements for different occupations may be calculated; the limitations of these \ methods; and how physical efficiency may be improved without i increasing the number of calories in diets. Examples are also cited J of the importance of knowledge of caloric values of food materials l from the point of view of economics otherwise. When read in i conjunction with the articles which are to follow on the subject of Is nutrition, it is hoped that this outline will form a practical basis b for the intelligent prescription of food materials.