A hundred years ago people believed that food should be well-chewed before swallowing, and that eating food too rapidly was not healthy. Here is what it said in a 1921 book:
Digestion begins in the mouth. But when food is improperly masticated, it enters the stomach with only slight alteration. The ptyalin of saliva is not present in sufficient quantity, under such conditions to produce any effect on the preliminary digestion of starches, with the result that the food passes through the duodenum practically unchanged, and in coarse particles, where it is likely to produce irritation. One authority says:
“Although much of the mechanical preparation and mixing of foods is of a necessity done in the stomach, some of it may advantageously be done in the mouth. The stomach should not be required to perform the function of the gizzard of a fowl.” –Human Foods, page 227.
Hasty eating, or bolting of food, is a fruitful cause of over-eating. The food does not remain in the mouth long enough under this condition, to give the satisfaction that it gives when thoroughly masticated; so, in an effort to satisfy the craving for food, more is taken than the body requires. This habit leads, moreover, to the taking of too large a quantity in too short a time, which serves to paralyze, as it were, the nerve impulses that communicate with the brain, and as a result the important message “Enough” does not reach the brain until an excess of food has been consumed.
When farinaceous foods (breads, cereals, potato, etc.) are well chewed and intimately mixed with saliva, they are more efficiently digested, and go farther, less food being required than when not well digested. Bread made from the entire grain requires more mastication before it can be swallowed than does spongy white bread, and itself promotes good digestion. Dry foods, which induce mastication should have a prominent place in the history.
The Science of Food and Cookery (1921) by H.S. Anderson