Saliva plays several crucial roles in the digestion of food:
- Moistening and Lubrication: Saliva moistens food, helping to form a soft, cohesive bolus that can be easily swallowed and passed through the esophagus into the stomach
- Enzymatic Breakdown of Starch: Saliva contains the enzyme salivary amylase (ptyalin) , which begins the chemical digestion of starch by breaking it down into simpler sugars such as maltose and dextrin right in the mouth, accounting for about 30% of starch digestion before the food reaches the stomach
- Initiation of Fat Digestion: Saliva also contains lingual lipase , which starts the digestion of fats, especially important in newborns whose pancreatic lipase is not fully developed
- pH Buffering and Protection: The bicarbonate and phosphate ions in saliva act as buffers to maintain a stable pH in the mouth, protecting teeth from acid erosion and aiding in remineralization of enamel
- Antibacterial Action: Saliva contains antibacterial compounds and enzymes (like lysozyme and immunoglobulins) that help control oral bacteria, protecting gums and teeth from infection and decay
- Facilitating Taste and Smell: By dissolving food particles, saliva allows taste buds to detect flavors and releases aromatic compounds that enhance the sense of smell, which indirectly supports digestion
In summary, saliva initiates digestion by enzymatically breaking down starch and fats, lubricates and forms the food bolus for swallowing, buffers oral pH, protects oral tissues, and enhances taste perception, all of which contribute to efficient digestion
