The mouth is an indispensable step in the digestive process. The sight, smell, and taste of food program the digestive system for the specific sequence of enzymatic secretions suited to the food being eaten. If one eats without appetite, or stressed, digestive juices don’t flow properly, and poor digestion results.
Chewing is crucial. Chunks of food in the stomach are never digested. Only the outer surface is worked on. In a word: indigestion.
Chewing food to a paste allows digestive enzymes to do their job. Adequate chewing prevents discomfort and the sense of heaviness that follows a poorly chewed meal.
Thorough chewing stimulates saliva production, an alkaline secretion. Saliva in the mouth contains the enzyme ptyalin, which aids digestion of starch. In a non-acidic environment, ptyalin begins breaking down starch into shorter chains by attacking certain links in the longer chains of starchy food. This facilitates starch digestion.