Salivary nitrite concentration does not accurately reflect systemic nitric oxide bioavailability or circulating nitrite levels.

Study: The Probiotic Streptococcus salivarius M18 Increases Plasma Nitrite but Does Not Alter Blood Pressure: A Pilot Randomised Controlled Trial

The study gave people a probiotic and found that nitrite in their blood went up, but nitrite in their saliva stayed the same — meaning saliva levels didn’t reflect what was happening in the blood. So, saliva can’t be trusted to show how much nitrite is in the bloodstream.

Study: Lowering salivary pH with sugar-containing gum augments salivary nitrite production and blood pressure reduction with dietary nitrate (beetroot juice).

This study found that when saliva becomes more acidic (from chewing sugary gum), more nitrite is made in the mouth, and that extra nitrite shows up in the blood — meaning saliva nitrite levels can tell us what’s happening in the bloodstream.

Study: A stepwise reduction in plasma and salivary nitrite with increasing strengths of mouthwash following a dietary nitrate load.

When people use certain mouthwashes, both the nitrite in their saliva and the nitrite in their blood go down together — meaning saliva nitrite can actually tell us what’s happening in the blood.