Chewing increases saliva production. Fear, fatigue and anxiety decrease salivary flow. Alternatively, the sight, smell or sound of food can stimulate saliva production. This relationship was noted by Dr. Pavlov nearly a century ago. By simply ringing a dinner bell, Pavlov conditioned dogs to salivate.
Saliva contains two enzymes that initiate fat and carbohydrate digestion.
The glands in the tongue secrete lingual lipase, which digests butter and other fatty foods. Ptyalin, another salivary enzyme, is produced mainly by the parotid gland. It breaks down bread, pasta, popcorn and other starch- containing foods into smaller sugar molecules. Ptyalin is inactivated by stomach acid. If the eyes are the windows to the soul, then the mouth is the door to the body.