124. Relish For Food

This involves two elements, the vigor of appetite and the attractiveness of the food in appearance and taste. When a person is hungry, in other words, has a "good appetite" and the food meets his approval in its kind and in the way it is prepared, the psychic condition is favorable to abundant secretions in the digestive tract. When, on the other hand, the appetite is "poor" or the food is distasteful, the necessary activity of the secretory glands receives no such stimulus. Forced nutrition does not conform to the best conditions for efficient nutrition. Unskillful or slovenly cooking, or an unwise selection of food may neutralize a vigorous appetite, or even breed dyspepsia.

125. The Amount Eaten

The evidence concerning the effect of the amount eaten at one meal upon the completeness of digestion is somewhat conflicting, but indicates that a full meal is somewhat less perfectly digested than when food is taken sparingly. Snyder1 found this to be so, though his results were not uniform. Sherman2 found a slight difference in protein digestion in favor of the restricted diet. It is fair to assume that with heavy eating the completion of digestion would require longer than when but little food is to be acted upon. Nevertheless, there is no evidence to show that with normal digestion there is any large amount of waste when food is taken in generous, but reasonable, amounts.

126. Effect Of Work

It is quite generally agreed on the basis of considerable experimental evidence that even severe labor does not depress digestion. In other words, a man at rest does not digest his food differently than when at work.

1Bul. 101, O.E.S., p. 64. 2 Bul. 121, O.E.S., p. 47.

127. Influence Of Accessory Articles Of Food

These include condiments, flavors, and stimulants which are used, not for their food value, which is small, but as a means of rendering food more attractive to the taste. It cannot be said that these, including alcoholic drinks, when used in reasonable quantity, depress digestibility. In fact, when properly used, they may, and probably do, exert a favorable influence upon digestion by promoting an increased flow of gastric juice through the psychic effect of a pleasing taste and through their reaction on the stomach membranes. Physicians use condimental substances to excite the secretions in cases of weak digestion. The essential conditions of good digestion do not justify the prevalent excessive and growing demand for such condiments as the peppers, garlic, mustard and vinegar, the long, intemperate use of which produces conditions on the part of the user that are unnatural and ruinous to the stomach.

128. Influence Of Cooking Food

In considering this factor, it is necessary to understand the effect of heat on different classes of food. As we have learned, certain proteins, especially the albumins, are coagulated and hardened by heat, even at a temperature considerably below the boiling point. Cooking also hardens, that is, makes more fibrous, many animal tissues. On the other hand, the effect of boiling and baking upon vegetable tissue is to disintegrate it, liberate starch grains from their cell inclosures, and make them available to the action of the digestive fluids, more or less dextrinize starch, and in some cases cause hydrolytic changes, as when in the cooking of apples and other fruits the pectins are changed to pectoses.

These facts lead to the conclusion, which is also sustained to some extent by experimental evidence, that the cooking of meats retards digestion, while with fruits and vegetables the same cause accelerates digestion. The advocates of raw vegetable foods should appeal only to persons with strong digestive powers. That such foods promote digestion as compared with those that are cooked, in the light of existing knowledge is an absurd proposition.