These results strongly point to the conclusion that previous estimates as to the quantity of food required are erroneous, and that man can not only live, but may continue in strength and health on much smaller amounts. It is highly probable that this discrepancy may be accounted for, at least to a considerable extent, by the assumption that much of the food ordinarily taken is rejected by the system, and passes out as waste, while, when small quantities are eaten, it is for the most part absorbed.
Mastication.—Thorough chewing of the food is absolutely essential for proper digestion. While it is true that this, like all other good things in life, may be, and often is, carried to an unnecessary extreme, it is certainly true that we would be infinitely better off if we were to go to the extent in this direction of so called “Fletcherism” rather than perform this most important function in an indifferent manner.
This rule applies with especial force to food of a starchy nature,—bread, potatoes, oatmeal, rice, etc. In order to digest food of this character it must be very thoroughly cooked and when finally placed upon the table it should be of such consistence that it requires chewing before it can be swallowed. Not only is this necessary from the standpoint of breaking up the larger particles into smaller ones, thus permitting the food to pass freely through the stomach and intestine, but it is of the greatest importance for it to be thoroughly soaked with the saliva during the process. It is thus of no advantage for starches to be served in a finely divided form—in fact it is directly the contrary, since under such circumstances it is almost always the case that such foods are swallowed without having been insalivated.
What has been said concerning the mastication of starches applies with almost equal force to other foods. Without exception their digestibility is much increased by thorough chewing. As the result of recent experiments carried out by means of the X-ray, it has been shown that particles of food of any considerable size will not pass from the stomach into the intestine; as often as an object of this kind attempts to force its way from the former into the latter the opening between the two closes, and as a consequence the food is retained in the stomach longer than it is in health—resulting in the course of time in catarrhal conditions of the organ just named, and an unnatural relaxation of its muscular walls. Under such circumstances the patient quickly develops symptoms of indigestion, and if his habits be not corrected the trouble gradually grows worse until the sufferer becomes a chronic dyspeptic.
Classes of Nutritive Substances.—All substances that are of any appreciable value in nutrition may be divided into those that are nitrogenous in character (albumins, legumins), the carbohydrates (starches and sugars) and compound ethers (fats). Of all these the nitrogenous foods are the most important, since they contain the material from which the great bulk of the body is largely composed, and at the same time there is every evidence that in case of need they may be broken up into chemical substances that may take the place of any of the other kinds of foods; upon nitrogenous food, then, a man may live alone, while this cannot be done on other articles of diet. The fats, starches and sugars are very closely related to each other, and it is generally believed that they subserve much the same end in the economy; by undergoing chemical change they furnish energy (heat and muscular force) and are undoubtedly largely responsible for the formation of the fats of the body. While there is some evidence that under certain conditions alcohol may be a food, its value is certainly very small, and it is not of sufficient importance to be considered in this connection. The ideal diet then for a healthy man is a proper proportion of nitrogenous (albuminous) food, along with a reasonable portion of fats, starches and sugars. Professors Voight and Atwater have calculated the following table, which fairly represents the amount of proteids, fats and carbohydrates that should compose the rations for twenty-four hours for the ordinary adult male.
ADULT MALE OF AVERAGE WEIGHT.
| At Rest. | Moderate Labor. | Severe Labor. | |
| Proteids | 110 grammes | 118 grammes | 145 grammes. |
| Fats | 50 " | 50 " | 100 " |
| Carbohydrates | 450 " | 500 " | 500 " |
The tables that follow, which were arranged by Hutchinson, give a very good idea of the generally accepted views as to the relative quantities of the different foods that are thought necessary for the average adult engaged in ordinary muscular work:—
Calories Defined.—It should be explained that the term “calorie” is one which has been adopted as a scientific expression for the fuel-value of substances undergoing oxidation, and in this connection refers to the heat-producing capacity of foods. The “calorie” is the amount of heat required to raise the temperature of one gramme of water 1°C. It has been estimated that starches, sugars and albumins liberate during combustion 4.1 calories per gramme, while fats produce 9.3 calories. It will be noted that in the tables just given the total number of calories is in each instance somewhere in the neighborhood of 3,500, which is considered to be about the number of heat units required by the average man at moderate muscular work. The weight of the average woman being less than that of the adult male, a reduction of about 20 per cent. from the foregoing figures would approximate the amount of food required by the former.