Have you ever wondered how much saliva you produce in an hour? How about a day, or a year? Hey, let’s go all in, how about in the average lifetime? Well, the answer is pretty surprising.
On a normal day, the average person produces between 0.5 and 1.5 liters of saliva – that’s more than a pint of milk. So, if we take a low average of say 0.7 liters per day, then that equals around 255.5 liters of saliva a year. Over an average lifetime of about 80 years, that comes to about 20,440 liters. That would be the equivalent of a small swimming pool full of saliva. That’s a lot of spit, but it is produced by our bodies for good reasons.
Saliva is a complex biofluid that plays numerous important roles in your mouth. For instance, it contains the enzyme amylase which breaks down starch, provides calcium and phosphate to help remineralize tooth enamel, and it’s a key gatekeeper in the defense against pathogenic microorganisms that enter your body through the oral cavity.
Saliva mostly consists of water (99 percent) and a mix of proteins, electrolytes, and digestive enzymes (1 percent).
It is produced by various glands, three major and numerous minor ones, located in your mouth. The three major glands – the parotid, submandibular, and sublingual glands – contribute 90 percent of the total saliva produced, while the remaining 10 percent is secreted by the minor ones.
In an unstimulated state (the resting state when you’re not eating), about two-thirds of the total volume of saliva is produced by the submandibular glands. The parotid gland comes into play when stimulated (usually by mastication, aka chewing, or taste stimulation) and is responsible for about 50 percent of the saliva in the mouth in this state. The sublingual glands, however, contribute a small percentage of saliva in both unstimulated and stimulated states.
Saliva has been used within medical traditions across the world for over 2,000 years. Ancient practitioners of traditional Chinese medicine believed that saliva and blood were “brothers”, as they both came from the same source in the body. According to Holy Scripture, Jesus spat in a blind man’s eyes in order to restore his sight (Mark 8:23), or applied it to mud to make a paste that was then used to anoint the blind person’s eyes (John 9:6). Renowned thinkers, such as Pliny the Elder (c. AD 23-79) and Albert the Great (1193-1280) both extolled the benefits of saliva for its ability to ward off serpents and bad luck, as well as promoting healing. Even as late as the nineteenth century, the supposed healing properties of saliva were still being celebrated by some physicians.
We no longer believe in saliva as a curative substance, but that does not mean it has no purpose in modern medicine. Today, it plays an important role as a diagnostic tool, as it can provide important insights into the body's overall state of health. As it is made up of so many components, saliva can contain various disease signal biomarkers which are useful for identifying illness as well as monitoring and predicting disease progression.
Moreover, the substance is readily available, and, unlike blood, it can be sampled through non-invasive methods, which makes it easy to analyze. Techniques are even been developed to use saliva as an indicator of prostate cancer.