As the portal of entry for food and the first step on the road to digestion, the mouth plays an important role in the process. Chewing—the mechanical part of digestion—begins the process. With our fast-paced, fast-food lifestyles, thorough chewing is a step many people often skip. But taking that little bit of extra time to thoroughly chew your food goes a long way toward promoting good digestion.

Your front teeth are designed to cut your food, while your back teeth are geared to grind it to a pulp. Saliva then coats your food and begins the chemical process of digestion. There are three large pairs of salivary glands located in the cheek (parotid), beneath the jaw (submandibular), and under the tongue (sublingual). These work with numerous tiny glands in the mucous layer of the lips and cheeks to produce saliva.

By moistening and coating your food, saliva makes it easier to swallow. In addition, saliva contains enzymes that chemically digest your food. These include amylase to break down starches and lipase to act on fats, along with a third enzyme called lysozyme. Lysozyme doesn’t digest food, but helps kill bacteria in the mouth and promote good oral hygiene.

The enzymes in your mouth and the enzymes further along the digestive tract act on the outer surfaces of food. The more surface area your food has—which you increase by thorough chewing—the more enzymes reach it and the more easily it is digested. Chewing becomes especially important when you eat a lot of fruits or vegetables, since these often have membranes that can’t be digested by the body—chewing becomes the only way to break through this membrane to the digestible part of the food.

Much of the enzyme activity in the mouth is short-lived, since enzymes work depending on how acidic or alkaline the environment is. The pH—a chemical measure of acidity or alkalinity—of the mouth is very close to neutral. So by the time your chewed food (called a bolus) hits the stomach where the pH drops to a more acidic level, the salivary enzymes cease to work.