We usually relate mastication to digestion. That is, mastication is the first stage of the digestive process, in which we prepare the food for swallowing and subsequent digestion (mechanical and chemical degradation of food).[1] In fact this is true, however, chewing is not an essential event for digestion, in the sense that the absence of this initial phase would not significantly impair the digestion of food. Swallowing the food without chewing properly does not prevent the digestion process itself, since the motor activities of the stomach and the enzymes of pancreas are able to compensate for possible deficiencies of chewing. The problem, therefore, is not related to the possibility of food digestion, but to the quality of this processing. The swallowing of larger particles, a natural consequence of masticatory problems, can significantly increase gastric emptying time, increase acid production, and favor gastric diseases such as gastritis and ulcers.[2]
In fact, the benefits of proper chewing go far beyond good digestion. The purpose of this article is to highlight the innumerable impacts of mastication on general health. The scientific evidence on the subject testifies the importance of the famous phrase "health begins with the mouth".
Mastication and Body Weight
Individuals with low masticatory performance are more likely to be obese.[3] This apparently strange relationship between mastication and body weight comes mainly from food selection. That is, masticatory difficulty usually leads individuals to choose softer, calorie foods, usually rich in carbohydrates and poor in fiber, vitamins, and proteins. In addition, the masticatory act is a stimulus to areas of the hypothalamus responsible for the sensation of satiety. In the long term, therefore, it is believed that proper chewing may contribute to a lower intake of food, and consequently to a lower gain of body weight.
Mastication and Endocrine Disorders
In addition to the impacts on body weight, animal studies indicate that the absence of adequate chewing may favor the development of glucose intolerance and diabetes. This was shown by a study carried out in mice, in which half of the animals ate a hard diet with a need to chew, while the other half ate the same diet in the form of purée, without the need for chewing. Non-chewing animals presented higher body weight, higher glycemic levels, and twice as likely to develop diabetes.[4] The main explanation for the positive effects of chewing on results is related to the ability of chewing to stimulate the release of insulin, the main glucose regulating hormone.
Mastication and Mental Health
Several well-controlled studies performed in both humans and animals point to a number of benefits of mastication over the central nervous system.[5] We can not forget that the mouth represents the most innervated region of the body, and its stimulation through chewing causes the activation of numerous brain areas, several of them responsible for the cognitive aspects of attention, reasoning, learning and memory.
When we chew, we literally cause intense blood flow to important brain areas, and this higher cerebral perfusion may be related to a better functioning of the microglia, the brain cells responsible for the cleaning of toxic substances that accumulate in nervous tissue. One such substance, the beta-amyloid protein, for example, may be related to the development of neurodegenerative diseases, such as Alzheimer's disease. Interestingly, several studies indicate that tooth loss may be a risk factor for the disease, although the cause of the problem is still unknown.[6-8]
After this brief summary on the main relationships between mastication and general health, it is clear that this function has more impacts on the body than simply contributing to digestion. Any professional responsible for restoring occlusion and masticatory function should therefore be aware of its relevant role in maintaining the proper functioning of the organism as a whole. All the evidence presented in this article reinforces the importance of the orthodontist as a differentiated professional, whose influence on the patients' lives certainly goes far beyond aesthetics.
References:
1. Gameiro GH, Magalhães IB, Szymanski MM, Andrade AS. Is the main goal of mastication achieved after orthodontic treatment? – A prospective longitudinal study. Dental Press Journal of Orthodontics. 22(3); 2017.
2. Sierpinska T, Golebiewska M, Dlugosz J, Kemona A, Laszewicz W. Connection between masticatory efficiency and pathomorphologic changes in gastric mucosa. Quintessence Int. 2007;38(1):31-7
3. Isabel CA, Moysés MR, van der Bilt A, Gameiro GH, Ribeiro JC, Pereira LJ. The relationship between masticatory and swallowing behaviors and body weight. Physiol Behav. 2015 Nov 1;151:314-9.
4. Nojima K, Ikegami H, Fujisawa T, Ueda H, Babaya N, Itoi-Babaya M, Yamaji K, Shibata M, Ogihara T. Food hardness as environmental factor in development of type 2 diabetes. Diabetes Res Clin Pract. 2006;74(1):1-7.
5. Weijenberg RA, Scherder EJ, Lobbezoo F. Mastication for the mind--the relationship between mastication and cognition in ageing and dementia. Neurosci Biobehav Rev. 2011;35(3):483-97.
6. Gatz, M.,Mortimer, J.A., Fratiglioni, L., Johansson, B., Berg, S., Reynolds, C.A., Pedersen, N.L., 2006. Potentially modifiable risk factors for dementia in identical twins. Alzheimers Dement. 2, 110–117.
7. Kim, J.M., Stewart, R., Prince, M., Kim, S.W., Yang, S.J., Shin, I.S., Yoon, J.S., 2007. Dental health, nutritional status and recent-onset dementia in a Korean community population. Int. J. Geriatr. Psychiatry 22, 850–855.
8. Noble JM, Scarmeas N, Papapanou PN. Poor oral health as a chronic, potentially modifiable dementia risk factor: review of the literature.Curr Neurol Neurosci Rep. 2013;13(10):384.