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I have a debate with some friends who believe that saliva is just basic, but with the enzymes which make them reactive with objects in our mouth, shouldn't it be an acid in this case?

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I can count four reasons that say saliva pH isn't the same among humans:

  1. As people age, the composition of saliva changes in their body; this is easily explainable with the fact that the body isn't performing the actions the same way as you grow up or become old.
  2. People have different eating habits; this will put the body in impression of producing especial kinds of enzymes and reduce\increase the production of certain factors in the saliva.
  3. People aren't the same when it gets to taking care of the insides of their mouth. You can be brushing your teeth twice as much as a close friend of yours does.
  4. Human digestive system isn't always performing its duties consistently and without "ups" and "downs" during the day, which has an important effect on enzymes produced.

And a sea of other reasons....

But, if we are to answer this question:

Saliva is a watery substance located in the mouths of animals, secreted by the salivary glands. Human saliva is 99.5% water, while the other 0.5% consists of electrolytes, mucus, glycoproteins, enzymes, and antibacterial compounds such as secretory IgA and lysozyme. Saliva, wikipedia

I'll also say that according to here, a healthy range of pH of saliva varies between 6.5 and 7.5 during the day, but is optimally between 6.5 and 6.8.

enter image description here Source

Thus, saliva is a very weak acid, or sometimes a very weak base. Considering something like that an acid or a base is like saying that the water we drink is a base and the water of the raindrops that fall from the sky of a peaceful country is acidic.

Saliva is really important for it's being a buffer.

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The pH value of resting whole saliva is slightly acidic, which varies between pH 5.75 and 7.05, and it increases with increasing flow rate up to pH 8. Besides flow rate, the pH also depends on the concentration of salivary proteins, bicarbonate and phosphate ions that have considerable buffering capacity. Bicarbonate concentration is ∼5–10 mM/L in resting conditions, and it may increase up to 40–60 mM/L with stimulation, whereas phosphate concentration is ∼4-5 mM/L in saliva rather independently from the flow rate. Besides bi-carbonate and phosphate, a significant amount of other ions are present to maintain the slightly hypotonic osmolarity of saliva. The most important ions are sodium (1–5 mM/L resting; 100mM/L stimulated), chloride (5 mM/L resting; 70 mM/L stimulated), potassium (15mM/L resting; 30–40 mM/L stimulated), and calcium (1.0 mM/L resting; 3–4 mM/L stimulated).Many other ions such as ammonium, bromide, copper,fluoride,iodide, lithium, magnesium, nitrate, perchlorate, thiocyanate, and so on can be found in the whole saliva in lower concentrations.

And appropriate ph is set up for optimum activity of enzyme especially during digestion process. enter image description here

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