The Practical Advantages Of Rational Feeding
( Originally Published 1913 )
Foods Easy and Difficult to Digest
THERE are persons who can, as it were, digest pebbles, while others no less healthy may suffer from indigestion after taking even the most easily digested foods. There is probably no other organ as capricious as the stomach. We shall not attempt here to deal with the nervous influences and idiosyncrasies affecting the stomach, but shall discuss only such disturbances as are caused by the food itself. In order that food may be easily digested, it must be in such a form as will permit of thorough action upon it by the gastric and intestinal juices; thus, a gelatinous substance like a pickled fish jelly is very easily digested. When, however, there is much connective tissue, as in an old chicken, digestion is more difficult; the tough, hard meat of old animals, which has so much connective tissue, is much more difficult of digestion than that of young animals. Lean boiled ham., being so free from connective tissue, is not only easily digested by the stomach, but by the intestine as well; the digestibility of a food depends not only upon the readiness with which it is tolerated by the stomach, but also by the intestine. Hard-boiled eggs are digested with difficulty by some stomachs, and are better assimilated in the intestine. Calves' brains are readily digested in the stomach, but less so in the intestine, since, according to Rubner, about 43 per cent. of such brain substance remains unassimilated.
The connective tissue in meat corresponds with the cellulose in vegetables. A fine starchy food without any such material, e.g., tapioca and sago, does not impose any labor on the stomach when well masticated, as it is not digested there; such a food does remain in the stomach for some time, but is only really made use of when it reaches the intestine. Thorough mastication, as already stated, is a prime necessity with starchy foods. A ripe banana is one of the most easily digested foods, when carefully masticated with the aid of plenty of saliva. It is advisable to allow such starchy foods to remain in the mouth for a short time, during which they should be moved about with the tongue and then be carefully chewed. When hard, dry foods containing much cellulose—such as the cereals, dried tubers, dried pears, or the black bread of the peasants—are taken, they not only remain a long time in the stomach, which must work hard to digest them, but are besides poorly assimilated in the intestine. We have mentioned on several occasions how much of certain foods remains unutilized during intestinal digestion. It is not our purpose to deter healthy persons from taking such foods, for it is, on the contrary, not inadvisable occasionally to eat small quantities of them. Unfortunately, the poor are obliged to eat them daily—without, however, actually ruining their health thereby.
In addition to the connective tissue and cellulose content, fat—especially lamb- and beef- fat—also interferes with digestion, particularly when it surrounds the more easily digested substances. Fat lamb is very indigestible. Dishes prepared with beef-drippings, so much used in England, are likewise not at all easily digested. Goose-fat is that which melts most readily, and butter comes next. Fine olive oil is well adapted for cooking; foods prepared with it are not indigestible. Fatty fruits and those containing cellulose, such as hazelnuts and old walnuts, are hard to digest.
The large amount of free fatty acids and pungent substances contained in some foods, and the acids, tannin, and ethereal oils of certain fruits, may all interfere with the digestion. Following is the list prepared by Penzoldt showing the digestibility of various foods:
FOODS REMAINING IN THE STOMACH ABOUT Two HOURS :
100 to 200 grams of drinking-water ;