Saliva is 99% water and 1% a complex mix of organic and inorganic molecules. That tiny 1% does an enormous amount of work: digesting food, protecting your teeth, fighting bacteria, and maintaining the chemical balance inside your mouth. A healthy adult produces roughly 0.75 to 1.5 liters of saliva every day, and its composition shifts depending on whether you’re eating, sleeping, or stressed.
Water and Electrolytes
The water in saliva keeps your mouth moist, helps dissolve food so you can taste it, and acts as a solvent for everything else saliva carries. Dissolved in that water are several key electrolytes: sodium, potassium, chloride, calcium, phosphate, and bicarbonate. These ions give saliva its electrical and chemical properties, but they also serve specific roles. Calcium and phosphate help repair and maintain the mineral surface of your tooth enamel. Bicarbonate acts as the primary buffering agent, neutralizing acids from food or bacteria.
Resting saliva sits at a pH of about 6.8, which is slightly acidic. When you start chewing and saliva flow increases, bicarbonate concentrations can jump from around 5 mmol/l up to 24 mmol/l, pushing the pH closer to 7.2. This buffering system is what protects your teeth after you eat something acidic or sugary. Without it, the acids produced by oral bacteria would erode enamel far more quickly.
Digestive Enzymes
Digestion starts in your mouth, not your stomach. Saliva contains two key enzymes that begin breaking down food the moment you start chewing. Amylase targets starches, the complex carbohydrates in bread, pasta, rice, and potatoes, splitting them into simpler sugars your body can absorb more easily. This is why a plain cracker starts to taste sweet if you chew it long enough: amylase is converting starch to sugar on your tongue.
The second enzyme, lingual lipase, begins breaking down fats. Its contribution is smaller than what happens later in the stomach and intestines, but it gives your digestive system a head start, particularly for infants who rely heavily on fat digestion from milk.
Mucins and Lubricating Proteins
The slippery feel of saliva comes from mucins, large glycoproteins made up of about 66% carbohydrate by weight. Mucins coat the surfaces of your mouth, tongue, and throat, creating a barrier that protects soft tissues from abrasion during chewing and shields against environmental and microbial irritants. Two main types, MUC5B and MUC7, handle slightly different protective roles in the oral cavity.
Not all salivary glands produce the same type of fluid. You have three major pairs. The parotid glands, located near your ears, produce a thinner, watery saliva rich in amylase. The sublingual glands, under your tongue, secrete a thicker, mucin-heavy fluid. The submandibular glands, along the jawline, produce a mix of both. This combination means your mouth gets both the enzymatic power to digest food and the lubrication to swallow it comfortably.
Your Mouth’s Immune System
Saliva is a surprisingly active part of your immune defense. Its main immunological weapon is secretory IgA, an antibody that acts as the first line of defense against pathogens entering through the mouth. IgA blocks bacteria and viruses from latching onto the surfaces of your cheeks, gums, and teeth.
Backing up IgA are two antimicrobial proteins: lysozyme and lactoferrin. Lysozyme directly attacks bacteria by breaking apart their cell walls. Lactoferrin binds to the mineral surfaces of teeth, preventing bacteria from colonizing and forming the sticky biofilms that lead to cavities. It can also degrade proteins that bacteria use to cause damage. These molecules don’t work in isolation. Lactoferrin and lysozyme physically bind to IgA, and research shows this pairing enhances their antimicrobial strength beyond what any of them achieve alone.
Together, these components inhibit the adhesion and growth of cavity-causing bacteria like mutans streptococci, making saliva one of your body’s most important natural defenses against tooth decay.
How Composition Changes With Stimulation
The saliva sitting in your mouth right now is chemically different from the saliva your body produces when you bite into a lemon. Resting saliva flows at roughly 0.3 to 0.5 ml per minute and has a relatively high concentration of antibacterial and acid-resistant proteins. When you start eating, flow rates can jump above 2 ml per minute. That stimulated saliva contains more bicarbonate for acid buffering but actually has lower concentrations of some protective proteins.
This tradeoff makes biological sense. At rest, your mouth needs maximum microbial defense. During eating, the priority shifts to diluting and neutralizing food acids, washing away debris, and ramping up enzymatic digestion. Your body adjusts the recipe in real time based on what your mouth needs most.
Hormones and Other Trace Molecules
Beyond its oral duties, saliva carries trace amounts of molecules from your bloodstream, including hormones, growth factors, and metabolic markers. Cortisol, your body’s primary stress hormone, filters into saliva at concentrations that reliably mirror blood levels. This is why saliva-based cortisol tests have become a standard, noninvasive way to measure stress responses in both clinical and research settings.
Saliva also contains growth factors like epidermal growth factor, which helps heal small wounds in your mouth (one reason minor cuts inside your cheek heal faster than similar cuts on your skin). Inflammatory markers like interleukin-6 show up in saliva during periods of stress, injury, or illness. Researchers have even developed wearable sensors, including mouthguard-based devices, that can monitor glucose or uric acid levels in saliva in real time, pointing toward a future where a simple spit test replaces a blood draw for routine health monitoring.
Saliva also carries trace amounts of neurotransmitters like serotonin and dopamine, along with other steroid hormones. While their concentrations are tiny, they’re measurable enough to serve as diagnostic windows into what’s happening elsewhere in the body.