Saliva is essential for a lifelong conservation of the dentition. There is an age-related decline in saliva output. Digestive enzymes found in the mouth include amylase for carbohydrate breakdown and lipase for fat digestion.

Saliva has a number of benefits:

The tooth surface is continuously protected against wear by a film of salivary mucins and proline-rich glycoprotein.
The early pellicle proteins, proline-rich proteins and statherin, promote remineralization of the enamel by attracting calcium ions.
Demineralization is retarded by the pellicle proteins, in concert with calcium and phosphate ions in saliva and in the plaque fluid. Some of these proteins are called histatins.
Several salivary (glyco)proteins prevent the adherence of oral microorganisms to the enamel pellicle and inhibit their growth.
The salivary bicarbonate/carbonate buffer system is responsible for rapid neutralization of acids.

Proteins in saliva
There are about 1,116 unique proteins found in human saliva glands. As many as 20 percent of the proteins that are found in saliva are also found in blood.

Saliva hormone testing
Salivary hormone test kits are aggressively marketed to perimenopausal and postmenopausal women and to men who want to supplement with over the counter hormones such as dhea or pregnenolone. The tests claim to measure the amounts of estrogens, progesterone, dhea, pregnenolone, and testosterone present in saliva. Those who sell these test kits claim that women and men can use the results of these tests to determine whether they need hormone replacement therapy. Apparently the initial test results would indicate the baseline saliva hormone level, and ongoing testing would signal whether hormone replacement has achieved its purposes.
     I am quite skeptical of these salive hormone tests for several reasons:

!. Saliva hormone testing is still relatively new compared to blood testing and good cross sectional levels have not been well establshed.

2. Different labs may have different ways of measuring and different results may be obtained by sending the same sample to different labs.

3. It is difficult to know what the actual tissue requirements for hormones are based on saliva levels. Even blood levels don't necessarily tell us what different tissues in the body require since blood levels are an average of all the tissues in the body, including fat cells, liver, skin, etc.

4. It is nearly impossible to know how much of a hormone to take or which one to take based on saliva hormone levels. There is a complex interaction between various hormones, they influence each other and various feeback loops are present.

In most cases, unless a person is hormone deficient, there are other dietary approaches, vitamins, herbs, and nutrients that can achieve a health benefit without the need for hormones.

Ethn Dis. 2013. Age-related decline in salivary dehydroepiandrosterone sulfate and associated health risks among African Americans. Dehydroepiandrosterone sulfate (DHEAS) declines with age and low endogenous DHEAS concentrations have been associated with obesity. In addition, DHEAS has been studied for its role in mood and wellbeing. However, limited data are available on salivary DHEAS concentrations in African Americans. Thus, we examined age-related changes in morning salivary DHEAS and the association between DHEAS and obesity risk factors among African Americans. The age-related decline in salivary DHEAS in African Americans is associated with cardiovascular risk factors, sleep quality, hassles and mood. Whether supplementing DHEAS levels in aging African Americans will improve health remains to be determined.

Cortisol testing for depression
A saliva test for teenage boys with mild symptoms of depression could help identify those who will later develop major depression,. Researchers in 2014 measured the stress hormone cortisol in teenage boys and found that ones with high levels coupled with mild depression symptoms were up to 14 times more likely to suffer clinical depression later in life than those with low or normal cortisol levels.

Saliva drug test
A saliva drug test is less intrusive than a urine or blood test. Saliva drug tests are becoming more common, but for legal purposes they are more difficult to interpret since there is a paucity of of nationally accepted standards or cutoff concentrations for detection.

Heart attack
Acta Odontol Latinoam. 2013. Oxidative stress assessed in saliva from patients with acute myocardial infarction. A preliminary study. This preliminary study showed that biomarkers of oxidative stress are detectable in saliva of patients with acute myocardial infarction.

Peanut Allergy through Saliva
People with peanut allergy and their partners should not kiss, or share utensils, if the partner has recently eaten peanut-containing food. Even with brushing, rinsing, or chewing gum, peanut allergen can remain in saliva after eating peanuts. Journal of Allergy and Clinical Immunology, September 2006.

Athletics, endurance training, marathon
Scand J Med Sci Sports. 2015. Effect of endurance training on dental erosion, caries, and saliva. The aim of this investigation was to give insights into the impact of endurance training on oral health, with regard to tooth erosion, caries, and salivary parameters. The study included 35 triathletes and 35 non-exercising controls. The clinical investigation comprised oral examination, assessment of oral status with special regard to caries and erosion, saliva testing during inactivity, and a self-administered questionnaire about eating, drinking, and oral hygiene behavior. In addition, athletes were asked about their training habits and intake of beverages and sports nutrition. For saliva assessment during exercise, a subsample of n = 15 athletes volunteered in an incremental running field test (IRFT). Athletes showed an increased risk for dental erosion. No differences were observed with regard to caries prevalence and salivary parameters measured during inactivity between athletes and controls. Among athletes, a significant correlation was found between caries prevalence and the cumulative weekly training time. In athletes after IRFT and at maximum workload, saliva flow rates decreased and saliva pH increased significantly. Higher risk for dental erosions, exercise-dependent caries risk, and load-dependent changes in saliva parameters point out the need for risk-adapted preventive dental concepts in the field of sports dentistry.