CHAPTER XVII
DIETARY STUDIES
244. Object of Dietary Studies.—The quantity of food which different families purchase varies between wide limits; a portion being lost mechanically in preparation and a still larger and more variable amount in the refuse and non-edible parts. If a record is made of all foods purchased and the waste and non-edible portions are deducted, the nutrients consumed by a family may be calculated by multiplying the weight of each food by the average composition. If such calculations be made, it will be found that in some families nearly a half pound per day of both protein and fat is consumed by adults, while in other families less than half of this amount is used. The object of dietary studies is to determine the source, cost, composition, and nutritive value of the foods consumed by different families; they also enable comparisons to be made of the amounts of nutrients purchased. Extensive dietary studies have been made by the United States Department of Agriculture, and the results have been published in various bulletins.[[76]]
245. Wide and Narrow Rations.—When the amount of carbohydrates in a ration is small in comparison with the protein, it is called a narrow ration, while a wide ration is one in which the carbohydrates are much in excess of the protein. When a ration contains 0.40 of a pound of protein, 0.40 of a pound of fat, and 1 pound of carbohydrates, it has a nutritive ratio of 1 to 4.8 and is a narrow ration. To calculate the nutritive ratio, the fat is multiplied by 2¼, the product added to the carbohydrates, and this sum divided by the protein. It is not possible to designate accurately the amount of protein and other nutrients that should be in the daily ration of all persons, because the needs of the body vary so with different individuals. Hard and fast rules governing the amounts of nutrients to be consumed cannot as yet be formulated, as our knowledge of the subject is too limited. It is known that both excessive and scant amounts are alike injurious. While the appetite may indicate either hunger or satiety, it alone cannot always be relied upon as a safe guide for determining the amount and kind of food to consume, although the demands of appetite should not be disregarded until it has been demonstrated beyond a doubt that it is not voicing the needs of nature. There has been a tendency which perhaps was a survival of the Puritanical ideas of the early days to stamp as hurtful whatever seemed desirable and pleasant; as examples might be cited the craving for water by fever patients, and for sugar by growing children, which have now been proven to be normal demands of nature.
246. Dietary Standards.—As a result of a large number of dietary studies and digestion experiments, dietary standards have been prepared. Atwater in this country and Voit in Germany have proposed such standards for men employed at different kinds of labor, as follows:
| Protein | Fat | Carbohy- drates | Fuel Value | Nutritive | |
|---|---|---|---|---|---|
| lb. | lb. | lb. | Calories | Ratio | |
| Man with little physical exercise | 0.20 | 0.20 | 0.66 | 2450 | 5.5 |
| Man with light muscular work | 0.22 | 0.22 | 0.77 | 2800 | 5.7 |
| Man with moderate muscular work | 0.28 | 0.28 | 0.99 | 3520 | 5.8 |
| Man with active muscular work | 0.33 | 0.33 | 1.10 | 4060 | 5.6 |
| Man with hard muscular work | 0.39 | 0.55 | 1.43 | 5700 | 6.9 |
In the table it will be seen that the quantity of nutrients increases with the labor to be performed. In order to secure the necessary heat and energy, rations for men at heavy labor contain proportionally more fat and carbohydrates than are required for light work. All dietary standards, however, should be regarded as tentative only. Opinions differ greatly on different points; for example, as to the amount of protein a ration should contain. This is a matter that can be determined only from extended investigations under a variety of conditions, and as yet results are too meager to formulate other than tentative standards. Chittenden has found that the body can be sustained on very much less protein than is called for in the standard ration.[[77]] The amount of protein in the ration should be ample to sustain the body weight and maintain a nitrogen equilibrium; that is, the income and outgo of nitrogen from the body should be practically equal.
Transcriber's Note: Fig. 58. is not of good quality,
but has been placed for information.
