Chemical Digestion Begins in the Mouth: The Role of Salivary Amylase

Digestion is both mechanical and chemical. The chemical breakdown of carbohydrates starts in the oral cavity.

The Process

• Salivary amylase (ptyalin) is secreted by the salivary glands (primarily parotid).
• As you chew, the enzyme mixes with food and begins hydrolyzing α-1,4-glycosidic bonds in starches (amylose, amylopectin).
• Products: maltose, maltotriose, and α-limit dextrins—shorter glucose chains.

Key Points

• Amylase works optimally at neutral pH (~6.7–7.0); it is inactivated by gastric acid.
• Only ~5–10% of total starch digestion occurs in the mouth, but this initiates the process and reduces gastric load.
• Thorough chewing increases surface area and enzyme contact time, enhancing digestion.

Clinical Relevance

Conditions reducing salivary flow (Sjögren's syndrome, radiation therapy, medications) or amylase production can impair initial carbohydrate digestion, though pancreatic amylase later compensates significantly.