The study of saliva is proving to be a rather interesting area for health, DNA testing and gene therapy. Personal genomics services like 23andMe use the cheek cells found in saliva to decode your DNA, but the saliva itself contains hundreds of proteins that keep the microbes that maintain your oral health alive. Apparently healthy saliva not only protects your teeth and tongue, but heals wounds faster and can even neutralise viruses like HIV. Dry mouth can actually have disastrous effects on aspects of daily life that most of us take completely for granted:
"... her mouth ended up so dry it wouldn't yield spit even when doctors tried milking her glands with a suction cup stuck inside her cheek. Unless she sipped water every few minutes, her mouth gummed up, her throat got scratchy, she croaked, and then she choked. Life's most humdrum events became tinged with new drama. She learned to favor slimy pastas and soups after a series of spectacular restaurant choking incidents--and a time, on a lunch date, when a wad of bread wedged fast under her lip, bulging it out like a chipmunk's cheek. "
Aside from DNA however, the chemical makeup of your saliva is apparently incredibly unique to each person, with no real geographical correlation, or even anything to do with age, gender or environment. Looks like it comes a lot more down to diet and hygiene, and also what types of medication you've been taking:
Differences in the bacterial composition among individuals from a particular place tended to be on par with the differences in the bacteria present between individuals from different places, indicating--to the team's surprise--that there were no geographical patterns. The researchers also did not find any correlation between the bacteria present and age, gender, or environmental factors, such as rainfall.
Maybe it might be worth playing a few rounds of Saliva of Fittest with myself, only using saliva samples taken at different types of day or after different meals. It could be interesting to see just how much the chemicals in my spit change and how it effects their digestive ability.
Scientists are also looking to saliva for as a new way to indicate the presence of certain diseases, making testing a whole lot easier than extracting blood. Saliva-testing would mean samples could be extracted again and again, introducing an accessibility for medicine that appears great on the surface, but I can't help but feel might have alternate consequences. In the context of biocommerce, eager medical scientists are sure to have dollar signs in their eyes at the potential ease with which they might be able to retain cellular disease information.
Here's what Wikipedia had on the subject:
Lubricant
Saliva coats the oral mucosa, mechanically protecting it from trauma during eating, swallowing and speaking. In persons with little saliva (xerostomia), soreness of the mouth is very common, and the food (especially dry food) sticks to the inside of the mouth.
Digestion
The digestive functions of saliva include moistening food and helping to create a food bolus. This lubricative function of saliva allows the food bolus to be passed easily from the mouth into the esophagus. Saliva contains the enzyme amylase, also called ptyalin, which is capable of breaking down starch into simpler sugars that can be later absorbed or further broken down in the small intestine. Salivary glands also secrete salivary lipase (a more potent form of lipase) to begin fat digestion. Salivary lipase plays a large role in fat digestion in newborn infants as their pancreatic lipase still needs some time to develop.[5]
Antimicrobial function
Saliva has both a mechanical cleansing action and a specific (immunoglobulins, e.g. IgA) and non-specific immunologic action (e.g.lysozyme, lactoferrin and myeloperoxidase). These factors control the micro-organisms that survive in the mouth. It also has a protective function, helping to prevent dental plaque build-up on the teeth and washing away adhered food particles. Saliva is also key in preventing ascending infections of the salivary glands (e.g. parotitis).
Ion reservoir/Buffer function
Saliva is supersaturated with various ions. Certain salivary proteins prevents precipitation, which would form salts. These ions act as a buffer, keeping the acidity of the mouth within a certain range, typically ph 6.2 - 7.4. This prevents minerals in the dental hard tissues from dissolving.
Hormonal function
Saliva secretes hormone gustin, which is thought to play a role in the development of taste buds[6]
Role in taste
Saliva is very important in the sense of taste. It is the liquid medium in which chemicals are carried to taste receptor cells (mostly associated with lingual papillae). Persons with little saliva often complain of dysgeusia (i.e. disordered taste, e.g. reduced ability to taste, or having a bad, metallic taste at all times).
Wound licking
A common belief is that saliva contained in the mouth has natural disinfectants, which leads people to believe it is beneficial to "lick their wounds". Researchers at the University of Florida at Gainesville have discovered a protein called nerve growth factor (NGF) in the saliva of mice. Wounds doused with NGF healed twice as fast as untreated and unlicked wounds; therefore, saliva can help to heal wound in some species. NGF has not been found in human saliva; however, researchers find human saliva contains such antibacterial agents as secretory IgA, lactoferrin, lysozyme and peroxidase.[7] It has not been shown that human licking of wounds disinfects them, but licking is likely to help clean the wound by removing larger contaminants such as dirt and may help to directly remove infective bodies by brushing them away. Therefore, licking would be a way of wiping off pathogens, useful if clean water is not available to the animal or person.
The mouth of animals is the habitat of many bacteria, some pathogenic. Some diseases, such as herpes, can be transmitted through the mouth. Animal and human bites are routinely treated with systemic antibiotics because of the risk of septicemia.
And finally, an interesting tidbit – Swiftlets, a type of bird, apparently construct their nests entirely from saliva, which becomes petrified when exposed to air (and also happens to be an incredibly expensive delicacy in China). This is indeed the perfect embodiment of the materiality of the body... I wonder if human saliva could be manipulated in a similar way?
