Harry Snyder

“ It has been said that 'a well man has no more need of predigested food than a sound man has for crutches.' If the digestive organs are out of order, it may be well to save them work, but troubles of digestion are often very complicated affairs, and the average person rarely has the knowledge needed to prescribe for himself. In general, those who are well should do their own work of digestion, and those who are ill should consult a competent physician."—Woods and Snyder. ”

“ Mechanical Condition of Foods.—The mechanical condition of foods as to density and structure of the particles and the extent to which they are disintegrated in their preparation for the table influences digestibility to a great extent. The mechanics of digestion is a subject that has not been extensively investigated, and it is one of great importance, as biological and chemical changes cannot take place if the food is not in proper mechanical condition. In general, the finer the food particles, the more completely the nutrients are acted upon by the digestive fluids and absorbed by the body. ”

“ Human Milk is not as rich in solid matter as cow's milk. It contains about the same amount of fat, one per cent more sugar, and one per cent less proteids. In human milk nearly one half of the protein is in the form of albumins, while in cow's milk there is about one fifth in this form. The fat globules are much smaller than those of cow's milk. In infant feeding it is often necessary to modify cow's milk by the addition of water, cream, and milk sugar, so as to make it more nearly resemble in composition human milk. ”

“ One of the chief objects in cooking food is to render it sterile. Not only do bacteria become innocuous through cooking, but various parasites, as trichina and tapeworm, are destroyed, although some organisms can live at a comparatively high temperature. Cooked foods are easily re-inoculated, in some cases more readily than fresh foods, because they are in a more disintegrated condition.
In many instances bacteria are of material assistance in the preparation of foods, as in bread making, butter making, curing of cheese, and ripening of meat. ”

“ Water unites chemically with various elements to form plant tissue and supplies hydrogen and oxygen for the production of organic compounds within the leaves of plants. In the animal economy it is not definitely known whether or not water furnishes any of the elements of which the tissues are composed, as the food contains liberal amounts of hydrogen and oxygen; it is necessary mainly as the vehicle for distributing nutrients in suspension and solution, and as a medium in which chemical, physical, and physiological changes essential to life processes take place. ”

“ Combination of Foods.—In a mixed ration the nutrients are generally more completely digested than when only one food is used. For example, milk is practically all digested when it forms a part of a ration, and it also promotes digestibility of the foods with which it is combined, but when used alone it is less digestible. [27] Bread alone and milk alone are not as completely digested as bread and milk combined. The same in a [Pg 224] general way has been observed in the feeding of farm animals,—better results are secured from combining two or more foods than from the use of one alone. ”

“ 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 ”

“ The fat from bread, when no lard or shortening has been added, is darker in color, more viscous, less soluble in ether, and has a lower iodine number, than fat from flour. The change in solubility of the fat is not, however, such as to affect food value, because the fat is not volatilized, and is only changed by the addition of a small amount of oxygen from the air. When wheat fat and other vegetable and animal fats are exposed to the air, they undergo changes known as aging, similar to the slight oxidation changes in bread making. ”

“ If the body is diseased, it cannot make the right uses of the food, and often the food is blamed when the trouble is due primarily to other causes. The fact that a diseased digestive tract is unable to utilize some foods is no valid reason why these foods should be discarded in the dietary of persons in normal health, particularly when the food is in no way responsible for the disease. ”

“ Individuality is one of the most important factors in digestion. Persons become accustomed to certain foods through long usage, and the digestive tract adapts itself to those foods, rendering sudden and extreme changes in the dietary hazardous. Common food articles may fail to properly digest in the case of some individuals, while with others they are consumed with benefit. What is food to one may prove to be a poison to another, and while general statements can be made in regard to the digestibility of foods, individual differences must be recognized. ”

“ It is difficult to make absolute comparisons as to the nutritive value of foods at different prices, because they differ not only in the amounts, but also in the kinds of nutrients. While it is not possible to express definitely the value of one food in terms of another, approximate comparisons may be made as to the amounts of nutrients that can be secured for a given sum of money when foods are at different prices, and tables have been prepared making such comparisons. ”

“ Hence it is [Pg 217] that the value of a food is dependent not alone on its composition, but also on its digestibility. The digestible or available nutrients of a food are determined by multiplying the per cent of each nutrient which the food contains by its digestion coefficient. For example, a sample of wheat flour contains 12 per cent protein, 88 per cent of which is digestible, making 10.56 per cent of available or digestible protein (12 × 0.88-10.56) . ”

“ In the animal body just the reverse of this process takes place,—the protein of the food undergoes a series of changes, and is finally eliminated from the body as an amid, which in turn undergoes oxidation and nitrification, and is converted into nitrites, nitrates, and ammonium salts. These forms of nitrogen are then ready to begin again in plant and animal bodies the same cycle of changes. Thus it is that nitrogen may enter a number of times into the composition of plant and animal tissues. Nature is very economical in her use of this element. ”

“ When the food is digested, the various nutrients undergo complete or partial oxidation, with the formation of carbon dioxid gas, water, urea (CH4N2O) , and other compounds. The feces consist mainly of the compounds which have escaped digestion. The various groups of compounds of foods do not all have the same digestibility; for example, the starch of potatoes is 92 per cent digestible, while the protein is only 72 per cent. The percentage amount of a nutrient that is digested is called the digestion coefficient. ”

“ There is but little difference between the fats and proteins of meats as to completeness of digestion,—the slight difference being in favor of the proteins. Some physiologists claim that the fat, which in some meats surrounds the bundles of fiber (protein) , forming a protecting coat, prevents the complete solvent action of the digestive fluid. Very fat meats are not as completely digested as those moderately fat. It is also claimed that the digestibility of the meat is influenced by the mechanical character, as toughness of the fiber. ”

“ Miscellaneous Compounds in Vegetables.—In addition to the general nutrients which have been discussed, many of the vegetables contain some tannin, glucosides, and essential oils; and occasionally those grown upon rich soils have appreciable amounts of nitrogen compounds, as nitrates and nitrites, which have not been built up into proteids. Vegetables have a unique value in the dietary, and while as a class they contain small amounts of nutrients, they are indispensable for promoting health and securing normal digestion of the food. ”

“ This change of bacterial flora in food materials is akin to the changes in the vegetation occupying soils. In each case, there is a constant struggle for possession. Bacteria take a much more important part in the preparation of foods than is generally considered. As a result of their workings, various chemical products, as organic acids and aromatic compounds, are produced. The organic acids chemically unite with the nutrients of foods, changing their composition and physical properties. Man is, to a great extent, dependent upon bacterial action. ”

“ Why is it necessary to consider the digestibility of food, as well as its composition? 673. Does the digestibility of a food necessarily indicate the economic uses that will be made of it by the body? 674. How is it possible for one food containing 10 per cent of digestible protein, and other nutrients in like amounts, to be more valuable than another food with the same per cent of digestible protein and other nutrients? 675. How is it possible for one food to contain less total protein than another food and yet be more valuable from a nutritive point of view? ”