A handbook of invalid cooking

by Mary A. Boland

It is probable that the fat which is used in the body either to be stored away or for energy, is derived from other sources than directly from the fat eaten. From experiments made by Lawes and Gilbert on pigs, it is evident that the excess of fat stored in their bodies must be derived from some other source than the fat contained in their food, and must be produced partly from nitrogenous matter and partly from carbohydrates, or, at least, that the latter play a part in its formation. It would appear from this that life might be maintained on starch, water, salts, and meat free from fat; but although the theory seems a good one, practically it is found in actual experiment[28] that nutrition is impaired by a lack of fat in the diet. The ill effects were soon seen, and immediate relief was given when fat was added to the food. Besides, in the food of all nations starch is constantly associated with some form of fat; bread with butter; potatoes with butter, cream, or gravy; macaroni and polenta with oil, and so forth. A man may live for a time and be healthy with a diet of albuminoids, fats, salts, and water, but it has not yet been proved that a similar result will be produced by a diet of albuminoids, carbohydrates, salts, and water without fat. Fat is necessary to perfect nutrition. Health cannot be maintained on albuminoids, salts, and water alone; but, on the other hand, cannot be maintained without them.

Probably the value of fats, as such, is dependent upon the ease with which they are digested. The fats eaten are not stored in the body directly, but the body constructs its fats from those eaten, and from other substances in food,—according to some authorities from the carbohydrates and proteids, and according to others from proteids alone.

Fats are stored away as fat, furnish heat, and are used for energy; at least, it is probable that at times they are put to the latter use. The fats laid by in the body for future use last in cases of starvation quite a long time, depending, of course, upon the amount. At such times a fat animal will live longer than a lean one.

Doubtless in the fat of food the body finds material for its fats in the most easily convertible form. Of the various fatty substances taken, some are more easily assimilated than others. Dr. Fothergill, in "The Town Dweller," says that the reason that cod-liver oil is given to delicate children and invalids is, that it is more easily digested than ordinary fats, but it is an inferior form of fat; the next most easily digested is the fat of bacon. When a child can take bread crumbled in a little of this fat, it will not be necessary to give him cod-liver oil. Bacon fat is the much better fat for building tissues. Then comes cream, a natural emulsion, and butter. He further says there is one form of fat not commonly looked at in its proper dietetic value, and that is "toffee." It is made of butter, sugar, and sometimes a portion of molasses. A quantity of this, added to the ordinary meals, will enable a child in winter to keep up the bodily heat. The way in which butter in the form of toffee goes into the stomach is particularly agreeable.

Carbohydrates. The principal carbohydrates are starch, dextrine, cane-sugar or common table sugar, grape-sugar, the principal sugar in fruits, and milk-sugar, the natural sugar in milk. They are substances made up, as before stated, of carbon, hydrogen, and oxygen, but no nitrogen. They are important food substances, but are of themselves incapable of sustaining life.

The carbohydrates, both starch and sugar, in the process of digestion are converted into glucose. This is stored in the liver in the form of glycogen, which the liver has the power of manufacturing; it then passes into the circulation, and is distributed to the different parts of the body as it is needed. (The liver also has the power of forming glycogen out of other substances than sugar, and it is pretty conclusively proved that it is from proteids, and not from fats. Carnivorous animals, living upon flesh alone, are found to have glycogen in their bodies.)

It is impossible to assign any especial office to the different food principles; that is, it cannot be said that the carbohydrates perform a certain kind of work in the body and nothing else, or that the proteids or fats do. The human body is a highly complex and intricate organism, and its maintenance is carried on by complex and mysterious processes that cannot be followed, except imperfectly; consequently, we must regard the uses of foods in the body as more or less involved in obscurity. It is, however, generally understood that the proteids, fats, and carbohydrates each do an individual work of their own better than either of the others can do it. They are all necessary in due amount to the nutrition of the body, and doubtless work together as well as in their separate functions. They are, however, sometimes interchangeable, as, for instance, in the absence of the carbohydrates, proteids will do their work. The carbohydrates are eminently heat and energy formers, and they also act as albumen sparers.

The body always has a store of material laid by for future use. If it were not for this a person deprived of food would die immediately, as is the case when he is deprived of oxygen. (Air being ever about us, and obtainable without effort or price, there is no need for the body to lay by an amount of oxygen; consequently only a very little is stored, and that in the blood.)

The great reserve forces of the body are in the form of fatty tissues, and glycogen, or the stored-away carbohydrates of the liver; the latter is given out to the body as it is needed during the intervals of eating to supply material for the heat and energy of daily consumption, and in case of starvation. That they are true reserves is shown by the fact that they disappear during deprivation of food. The glycogen, or liver-supply, disappears first; then the fat (Martin). The heat of the body can be maintained on these substances, and a certain amount of work done, although no food except water be taken.