<Li> Opiorphin, a pain - killing substance found in human saliva </Li> <Li> Haptocorrin, a protein which binds to Vitamin B12 to protect it against degradation in the stomach, before it binds to intrinsic factor </Li> <P> There is much debate about the amount of saliva that is produced in a healthy person per day; estimates range from 0.75 to 1.5 litres per day while it is generally accepted that during sleep the amount drops to nearly zero . In humans, the submandibular gland contributes around 70--75% of secretion, while the parotid gland secretes about 20--25% and small amounts are secreted from the other salivary glands . </P> <P> Saliva contributes to the digestion of food and to the maintenance of oral hygiene . Without normal salivary function the frequency of dental caries, gum disease (gingivitis and periodontitis), and other oral problems increases significantly . </P>

How much saliva does a human produce in a day