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Saliva has hundreds of components that can be used to detect systemic diseases or as evidence of exposure to various harmful substances. In addition, it provides biological markers of a person's health and disease status. Today, the field of saliva research is advancing rapidly due to the use of novel technological approaches. The amount and composition of human saliva secreted depends on many factors. For example, genetics, age, gender, blood type, oral hygiene, diet, chewing and physical activity. Also, it depends on the physiological, psychological and hormonal state of the person, among other factors.

Saliva is a complex fluid consisting of secretions from the major and minor salivary glands. It is estimated that there are between 450 and 750 minor accessory salivary glands, located in the tongue, oral mucosa and palate, except in the anterior part of the hard palate and gums. The average daily volume of saliva production is 500 to 1,000 ml (17 to 34 fluid ounces). The submandibular glands produce 70% of the total volume, the parotid glands 25% and the sublingual glands around 5%. The greatest volume of saliva is produced before, during and after meals, reaching its maximum peak around 12:00 pm and falling considerably at night, while we sleep.  

Protective functions of saliva

1. Washing and cleaning the oral cavity, mucosa and teeth
2. Integrity of the oral mucosa – if the mucosa is broken, the risk of oral infectious diseases will increase
3. Lubrication and keeping the oral cavity, mucosa and teeth moist
4. Antimicrobial – contains the enzyme lysozyme with antibacterial action
5. Growth factor, which helps in the healing of oral tissues
6. Remineralization – protects tooth enamel against cavities and plaque buildup
7. Maintains neutral pH in the mouth, by neutralizing acids ingested or produced by microorganisms in the oral cavity

Functions of saliva related to feeding and speech

1. Food preparation before swallowing
2. Prevention of dental cavities
3. Perception of taste, flavor and texture of food
4. Facilitates speech by hydrating the mucosa of the pharynx and oral cavity
5. Digestion – initiates the process of carbohydrate digestion with the salivary enzyme amylase (ptyalin) and facilitates the digestion of fats with the salivary lipase enzyme

Investigation

Dental cavities - In recent decades, attention has focused on the use of saliva for bacteriological tests that give an indication of dental caries risk. For example, the absence of the statherin protein in saliva is associated with a higher prevalence of dental caries. 

Oral infectious diseases – ABH blood group antigens, which are secreted in saliva, can alter the interaction of microorganisms and certain salivary substances. This modification interferes with the development and prevention of oral infectious diseases. 

Systemic diseases – The components of saliva act as a "mirror of the body's health." Many studies demonstrate that saliva sample analysis is a convenient means of evaluating physiological conditions, the serum concentration of a drug, the severity of a disease, and plasma levels of hormones. The systemic diseases studied that affect the salivary glands and saliva are: 

• HIV+
• Sarcoidosis*
• Hypertension 
• Cystic fibrosis
• Renal disease
• Autoimmune diseases such as rheumatoid arthritis
• Cancer particularly malignancies of the oral cavity
• Hormonal disorders such as diabetes mellitus and thyroiditis
• Neurological diseases such as cerebral palsy, Parkinson's and Alzheimer's
• Metabolic disorders such as malnutrition, dehydration and vitamin deficiencies
• Alcoholic liver cirrhosis- The parotid enlarges in many patients, reducing salivary flow by 50%.

In summary, la saliva es un fluido corporal importante para detectar situaciones fisiológicas y patológicas del cuerpo humano. Tan pronto percibas algún cambio en el sabor, olor, consistencia o cantidad de la saliva debes consultar con tu médico primario.

*It is an inflammatory disease that affects multiple organs of the body, particularly the lungs and lymph nodes, forming abnormal masses or nodules (granulomas).

Carmen M. Pérez Velázquez