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The Digestive Process: Digestion Begins in the Mouth

Digestion is a multistep process that begins the moment you put a piece of food in your mouth or sip a drink. 

Breaking it down

When you begin chewing, glands in your mouth and throat begin to secrete saliva. This process can start with the sight or smell of food. The liquid aids digestion, moistens your mouth, reduces infections in the mouth and throat, and helps protect your teeth and gums. You have three major pairs of salivary glands:

  • Parotid glands, the largest, are on both sides of your face, in front of your ears

  • Submandibular glands are underneath your jawbone

  • Sublingual glands are underneath your tongue

Your upper digestive tract and your esophagus also contain smaller clusters of salivary glands. Saliva contains special enzymes that help digest the starches in your food. An enzyme called amylase breaks down starches (complex carbohydrates) into sugars, which your body can more easily absorb. Saliva also contains an enzyme called lingual lipase which breaks down fats.

A condition known as dry mouth (xerostomia) occurs when you don’t have enough saliva in your mouth. This can make it difficult for you to chew and swallow food. Stress or dehydration can cause occasional xerostomia. Certain medicines or more serious conditions, such as diabetes, can also cause it. To reduce your chance of dry mouth, drink plenty of water and avoid caffeinated or alcoholic beverages. These can make dry mouth worse.

How does it taste?

When your saliva begins to break down your food, the taste buds on your tongue and on the roof of your mouth sense how the food tastes. Taste buds contain gustatory cells, which send taste signals to the brain. This is how you sense the five basic tastes of food: sour, sweet, salty, bitter, and savory. Nerves in your nose, mouth, eyes, and throat let you experience the other qualities of food, like the heat of spicy foods and the coolness of peppermint.

The role of your teeth

Your teeth are also part of the digestive process. Teeth break down food for swallowing and further digestion. The incisors, located in the middle front of the lower and upper jaws, cut and gnaw pieces of food. The molars, in the back of the mouth, grind and chew. To keep your teeth at their healthiest, follow these simple preventive measures:

  • Eat a healthy diet rich in protein, fruits and vegetables, calcium, and whole grains.

  • Limit eating and drinking between meals.

  • Limit sugary foods and beverages.

  • Brush your teeth twice a day with fluoride toothpaste, and floss once a day.

  • Visit your dentist regularly for professional cleanings and exams.

On to the stomach

After you chew and swallow your food, it enters your esophagus. This tube connects your throat to your stomach. A series of muscular contractions, known as peristalsis, pushes your food downward and into your stomach. There, it mixes with more digestive enzymes to continue the breakdown process.