5. Animal foods have the advantage of vegetable foods in that they contain more protein, and that their protein is more easily digested. (Atwater.)
A diet largely of animal food leaves very little undigested matter. The albuminoids in all cases are completely transformed into nutriment. Fat enters the blood as a fine emulsion.
Absorption. The general rule of absorption is that food is taken into the circulation through the porous walls of the alimentary tract as rapidly as it is completely digested. A large portion of liquid is immediately absorbed by the blood-vessels of the stomach.
Adaptation of Foods to Particular Needs and Conditions. The demands of different individuals for nutrients in the daily food vary with age, occupation, and other conditions of life, including especially the peculiar characteristics of people. No two persons are exactly alike in their expenditure of muscular and nervous energy, so no two will need the same amount or kind of nutriment to repair the waste.
A man who digs in a field day after day expends a certain amount of muscular energy. A lawyer, statesman, or author who works with his brain instead of his hands uses nervous force, but very little muscular. Brain and muscle are not nourished exactly by the same materials; therefore, the demand in the way of nutriment of these two classes will not be the same.
The lawyer might find a feast in a box of sardines and some biscuit, while the field laborer would look with contempt upon such food, and turn from it to fat pork and cabbage. This is no mere difference in refinement of taste, but a real and instinctive difference in the demands of the two constitutions. Sardines supply to the brain-worker the material he needs, and the pork and cabbage to the laborer the heat and energy he expends.
In health the sense of taste is the best guide to what is demanded by the system, and may as a general rule be followed; but in sickness that will not do, as the sense of taste in particular is disturbed by most forms of disease.
When a patient is very ill only the simplest foods will be used, and those will be prescribed by the physician; but when a patient is out of danger, and the necessity for variety comes, then the nurse, by preparing or suggesting dishes, may do much toward restoring the person to health and strength.
As a very large percentage of diseases arise from imperfect nutrition (as large as eighty per cent. being given by some writers), the sense of taste is usually very much disturbed and dulled in illness; therefore those kinds of food which are savory, and at the same time easy of digestion and nutritious, should be selected. The savory quality is very important. A person in health may endure badly cooked food and monotony in diet; a person recovering from an illness cannot but suffer by it.
A nurse will find a pleasant field for the exercise of ingenuity in selecting and preparing such dishes as shall (1) be suited to the digestive powers of the patient; (2) shall be savory; (3) shall be sufficiently varied to supply all those materials which the depleted and exhausted body needs; and (4) shall be in such judicious quantity as shall increase nutrition, but never overtax the digestive powers.