The human body produces about 1 to 2 litres of saliva each day, a complex biofluid that moistens food, begins digestion with enzymes and plays multiple protective roles for teeth and oral tissues.
Production and volume
Saliva is secreted continuously by the major and minor salivary glands, with daily output commonly estimated between 1 and 2 litres in a healthy adult. Production varies with factors such as hydration, time of day, diet, medication and nervous system activity, and it increases reflexively during eating or when anticipating food.
Digestive role
Saliva contains digestive enzymes, notably amylase and lingual lipase, which begin the chemical breakdown of carbohydrates and, to a lesser extent, fats while food is still in the mouth. This initial processing improves swallowing, enhances taste perception and prepares food for further digestion downstream in the gastrointestinal tract.
Oral protection
Beyond digestion, saliva neutralises acids, buffers pH, supplies calcium and phosphate for remineralising enamel and contains antimicrobial proteins such as lysozyme, lactoferrin and immunoglobulins that help control bacterial growth. These combined functions protect teeth from decay and support overall oral health.
Mechanical functions
Saliva lubricates the mouth and throat, forming a cohesive bolus for safe swallowing and protecting mucous membranes from abrasion and drying. It also aids speech by keeping oral tissues supple and facilitates oral hygiene by washing away loose food particles and surface microbes.
Clinical relevance
Reduced saliva production, or xerostomia, increases the risk of dental caries, oral infections and difficulty eating or speaking; it can result from medications, radiation therapy, autoimmune disease or dehydration. Maintaining adequate hydration, reviewing medications with a clinician and seeking dental advice help manage symptoms and protect oral health.
Quick related facts
- Daily volume: about 1–2 litres per day.
- Key enzymes: amylase; lingual lipase.
- Protective roles: acid neutralisation; enamel remineralisation; antimicrobial action.
- Mechanical roles: lubrication for swallowing and speech; debris clearance.
- Warning sign: persistent dry mouth merits medical or dental evaluation.