Nutritive value

“ Prominence is given in this work to those foods, as flour, bread, cereals, vegetables, meats, milk, dairy products, and fruits, that are most extensively used in the dietary, and to some of the physical, chemical, and bacteriological changes affecting digestibility and nutritive value which take place during their preparation for the table. Dietary studies, comparative cost and value of foods, rational feeding of men, and experiments and laboratory practice form features of the work. ”

“ It is well known, however, that the mechanical state of the food has a most important influence on its nutritive value. Thus, for example, the presence of a large quantity of woody fibre protects the nutritive substances from assimilation, and seeds with hard husks pass unchanged through the animal, although, so far as their composition alone is concerned, they may be highly nutritive; and the loss of a certain quantity of many varieties of food in this way is familiar to every one. ”

“ The unique value of sugar depends upon its intelligent use and its proper combination with other foods, particularly with those rich in the nitrogenous compounds or proteids. Sugar alone is incapable of sustaining life, but combined with other foods is a valuable nutrient. ”

“ In seeds the elements of nutrition exist not only in the most highly elaborated, but also in the most concentrated state; hence their nutritive value is greater than that of any other class of food substances. ”

“ Relation.—The value of a food depends largely upon the relation of one group of nutrients to another. Proper nutrition can only be obtained when a sufficient amount of flesh-forming as well as of heat-producing nutrients are present, when the “nutritive ratio” is properly balanced for the particular purpose in view, be it the growth of the child, the maintenance of the body, the restoration of matter consumed by labor of body or brain, or the supply of heat to make up for cold surroundings. ”

“ It is possible to confine one’s choice to some which contribute little besides fuel to the diet, such as rice and white flour, or to include those which are rich in other essentials, such as oatmeal. It is difficult to express briefly this difference in foods in any concrete fashion, but recently a method of grading or “scoring” foods has been introduced which may help to make clearer the relationship between nutritive value and general economy. ”

“ The great nutritive value of our food is found in the cereals, the meats, the fruits, and vegetables which we consume. A description of foods of this class, the places of their growth, the conditions under which they are matured and marketed, the problems which relate to their storage and transportation, their composition in respect of nutrition and digestibility, the dangers which may accrue from their decay, and the adulterations or sophistications to which they may be subjected are matters of the greatest public importance. ”

“ 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. ”

“ Cocoa, although a valuable beverage, adds but little in the way of nutrients to a ration unless it is made with milk. The value of a food should be based upon its composition as determined by chemical analysis, its digestibility as founded upon digestion experiments, and its palatability and mechanical structure. ”

“ This is done in Table VI., which shows the amounts of available nutrients contained in the quantities of different food materials that may be purchased for one shilling at prices common in England.
When proper attention is given to the needs of the body for food and the relation between cost and nutritive value of food materials, it will be found that with care in the purchase and skill in the preparation of food, considerable control may be had over the expensiveness of a palatable, nutritious and healthful diet. ”

“ Object.—Rational feeding of man has for its object the regulation of the food supply in accord with the demands of the body. It is based upon the same principles as the rational feeding of animals; in each, the best results in the way of health, amount of labor performed, and economy are secured when the body receives nutrients sufficient for the production of heat and energy and for the repair of worn-out tissues. Rational feeding is simply regulation of the food, both as to kind and amount, to meet the needs of the body. ”

“ Mixed Dietary Desirable.—Experiments in the feeding of farm animals show that the best results come from the combination of a number of foods to form a mixed ration, rather than from the use of one food alone, [79] for in this way the work of digestion is more evenly distributed, and a higher degree of efficiency is secured from the foods consumed. The same is true in human feeding; the best results are secured from a mixed diet. Ordinarily, about two fifths of the nutrients of a ration are derived from animal and three fifths from vegetable sources. ”

“ Vegetables are by no means the most nutritious diet, as water enters largely into their composition; but food to supply perfectly the needs of the vital economy, must contain water and indigestible as well as nutritive elements. Thus they are dietetically of great value, since they furnish a large quantity of organic fluids. Vegetables are rich in mineral elements, and are also of service in giving bulk to food. An exclusive diet of vegetables, however, would give too great bulk, and at the same time fail to supply the proper amount of food elements. ”

“ The use of fruits, herbs, and vegetables for medicinal purposes is based upon the presence of compounds possessing well-defined medicinal properties. As a rule food plants do not contain appreciable amounts of such substances, and the use of food for medicinal effect should be by the advice of a physician. The physiological properties of some foods are due to bacterial products. See Chapter XX.
239. Individuality.—Material difference in digestive power is noticeable among individuals. Digestion experiments show that one person may digest 5 per cent more of a nutrient than another. ”

“ Food Value.—When the nutrients alone are considered, fruits appear to have a low food value, but they should not be judged entirely on this basis, because they impart palatability and flavor to other foods and exercise a favorable influence upon the digestive process. In the human ration fruits are a necessary adjunct.
59. Apples.—Apples vary in composition with the variety and physical characteristics of the fruit. In general they contain from 10 to 16 per cent of dry matter, of which 75 per cent, or more, is sugar or allied [Pg 50] carbohydrates. ”

“ Experiments with the cooking of carrots show that if a large amount of water is used, 30 per cent or more of the nutrients, particularly of the more soluble sugar and albumin, are extracted and lost in the drain waters. ”

“ NUTRITIVE VALUES.—The per cent of nutrients in a food does not always indicate the quantity of nourishment it will yield. The nutrient must be in a condition to be absorbed. Wheat grains contain as much protein when whole as when ground into meal, yet uncooked whole wheat grains yield little nourishment to the body. They pass through the system with much nutriment unextracted. Even if the unbroken grains are thoroughly cooked, they will not furnish as much nourishment to the body as they will when in the form of meal. ”

“ Special treatment, as steaming or malting, is sometimes given to impart palatability and to lessen the time required for cooking. As a class, the cereal foods are clean, nutritious, and free from adulteration. Extravagant claims are sometimes made as to their food value, and frequently excessive prices are charged, out of proportion to the cost of the nutrients in the raw material. Within recent years the number of cereal preparations has greatly increased, due to improvements and variations in the methods of manufacture. ”

“ The quantities of nutrients in these food materials are approximately as follows:
Ration for Man at Moderate Work
It is to be noted that this ration contains approximately the amount of protein called for in the standard [Pg 266] ration, while the fat is slightly more and the carbohydrates are less. The food value of the ration is practically that called for in the standard. This ration is sufficiently near the standard to supply the nutrient requirements of a man at light muscular work. To supply palatability, some fruit and vegetables should be added to the ration. ”

“ It is believed that a better understanding of the subject of nutrition will suggest ways in which foods may be selected and utilized more intelligently, resulting not only in pecuniary saving, but also in greater efficiency of physical and mental effort. ”

“ No single natural order contains plants that supply all the elements essential to the nutrition of the body and the right composition of the blood. The graminaceous and leguminous articles of food, for instance, are numerous, but not various; they all afford the same or analogous albuminous elements, which have about the same nutrient value as the corresponding substances in animal food, and hence health and vigor cannot be sustained on a diet of flesh, combined with wheat, rice, and oatmeal or with beans and peas, or with all of them together. ”

“ On the other hand, it is equally indisputable that there are many cheap kinds of vegetable food which are as nutritive or more nutritive than flesh meat ; and it has repeatedly been shown that every shilling spent on beef or mutton might have purchased five or six times the amount of nutriment if expended on peas, beans, lentils, wholemeal bread, or oatmeal. ”

“ An animal regularly fed eats till it is satisfied, and no more than is requisite. A part of the nutritive elements in hay and other forage plants is needed to keep an animal on its feet,—that is, to keep up its condition,—and if the nutrition of its food is not sufficient for this the weight decreases, and if it is more than sufficient the weight increases, or else this excess is consumed in the production of milk or in labor. ”

“ Position V.—A flesh diet, in common with the use of strong drink, impairs the tone of the nutritive apparatus, by which its ability to work up raw material and manufacture it into sound, well finished vital fabric, is diminished, and of course the appetite or call for food is satisfied with a less quantity of the raw material. This fact has given rise to the opinion that animal food contains more nutriment than vegetable. ”

“ But let the consumption drop to an average of only 138 gr., which is the smallest amount necessary for the bare maintenance of life, and in a year or two (not at once, for every body contains a store of nitrogen) important modifications of the nutritive processes, with distinct predispositions to disease, will inevitably be established. ”

“ This example is also given to impress upon the mind of the practitioner the great importance of proportioning nutritive elements in diet so that the patient will not be overfed on some elements while underfed on others. It is absolutely essential, in order to know what effect a substance will have in the laboratory, or in the body, to know not only of what it is composed, but with what substances and in what proportions it is combined. ”

“ If these are merely exceptional cases, we need to know it; but if, on the other hand, it is possible for mankind in general to maintain proper nutritive conditions on dietary standards far below those now accepted as necessary, it is time for us to ascertain that fact. ”

“ Before putting “vegetalism” into practice the first point is to know whether the foods of “vegetal” origin contain, and are susceptible of producing regularly, the divers nutritive principles indispensable to the organisation of an alimentary diet. The principles are the following:—Proteid or albuminoid substances; hydrocarbonated and sweet substances fatty substances; mineral matters, alkalis, lime, magnesia, phosphates and chlorides, etc. In most compound foods, no matter of what origin, mineral materials almost always exist in sufficient quantities. ”

“ For all who are occupied with severe and continuous mechanical labor, a mixed diet, of which cereals and legumes form a large portion, and meat, fish, eggs, and milk form a moderate proportion, is more nutritious and wholesome than chiefly animal food. For those whose labor is chiefly mental, and whose muscular exercise is inconsiderable, still less of concentrated nitrogenous food is desirable. A liberal supply of cereals and legumes, with fish, and flesh in its lighter forms, will better sustain such activity than large portions of butcher's meat twice or thrice a day. ”

“ As age advances, the consumption of meat and all flesh foods should be decreased and that of fruit and vegetables, especially those of bulky character and low food value, such as lettuce, tomatoes, carrots, turnips, salsify, oyster-plant, watercress, celery, parsnips, should be increased. ”

“ It is not our design to discuss here the dietetics or even the chemistry of food. There is, however, one branch of the subject that calls for a passing remark—the value of foods for special purposes. As the agriculturist is now carefully considering the adaptation of soils to the various kinds of vegetation, and is also inquiring into the character of those fertilizers that will continue and increase the growth-producing qualities of his land, so the physiologist is seeking to discover the special value of different aliments for all conditions of health and disease. ”