The Surprisingly Important Business of Chewing

OVERVIEW: Mastication is far more than simply the mechanical act of grinding food into smaller pieces that are easier to swallow.  Mastication engages the nervous system, contributes to the early stages of digestion, influences appetite and satiety, provides mechanical stimulation to the jawbone, and takes place within a complex oral microbiome.  Tooth loss and impaired masticatory function have been associated with cognitive decline, although researchers are still working to understand the mechanisms and whether these relationships are causal, and maintaining the ability to masticate matters to far more aspects of health than we have traditionally recognized.

When I was much younger, we learned the word “Masticate,” and you can perhaps imagine the endless laughs we had about it.  Mastication, haha.  “Do you masticate?” … I’ve heard mastication jokes in movies and TV shows, and I never gave it much thought at all, beyond the obvious ‘hilarity’, and I am not alone in that oversight of what mastication really means.

Though mastication is a complex biological process that affects far more than the mouth,  discussions about dental health focus too frequently on cavities, gum disease, and cosmetic concerns.  We all need mastication, and we are going to call it ‘chewing’ in this article.

Chewing influences digestion, neurological activity, appetite and metabolic signaling, and even the structure of the jaw.  When the ability to chew is impaired because of tooth loss or untreated dental disease, the effects may extend well beyond the mouth.  Some of these connections are well established; others are still being investigated.

Emerging research suggests that chewing is much more than simply the mechanical act of grinding food.  It is a neurological, mechanical, digestive, and metabolic activity—and the more closely we look at it, the harder it becomes to regard chewing as an insignificant part of eating.

Chewing as a Neurological Activity

Chewing is coordinated by an intricate network of nerves and muscles.  Sensory signals from the teeth, gums, jaw muscles, and temporomandibular joint (TMJ) travel through branches of the trigeminal nerve to the brainstem and cerebral cortex.  This sensory feedback helps regulate the force, rhythm, and coordination of chewing movements, and at the same time, chewing produces sensory and motor activity in multiple areas of the brain.

Studies using brain-imaging techniques have shown activation in regions involved in sensory processing and cognition during chewing, and increased cerebral blood flow has also been observed, including in areas associated with learning and memory.  Researchers have proposed several mechanisms for these effects, including changes in trigeminal signaling and neurovascular activity.  This does not mean that chewing has been proven to prevent neurological disease.  But it does establish something rather interesting: Chewing is a neurological activity.

Our brains are not simply waiting to swallow the food after we chew it.  They are participating in the chewing, itself.  Perhaps the most intriguing question raised by the neurological effects of chewing is what they might mean for cognition.

Several observational studies have found associations between tooth loss, impaired masticatory function, and cognitive decline in older adults.  Researchers have proposed several possible explanations.

One possibility involves the sensory stimulation of chewing, and another involves nutrition. People who cannot chew comfortably may alter what they eat, sometimes avoiding foods that are difficult to chew, including certain vegetables, nuts, meats, and other nutrient-dense foods.  Sometimes, whole foods are completely passed over for processed, or ultra-processed food, which is a concern, as well.  Over time, changes in food choices can affect nutritional status and, consequently, overall health.

Inflammation may also be part of the picture. Periodontal disease is associated with systemic inflammatory processes, and inflammation has been implicated in a wide range of chronic diseases, including some neurological conditions.

And there is another particularly interesting piece of the puzzle: restoring chewing function after tooth loss may matter too. A 2025 systematic review and meta-analysis of six observational studies involving more than 24,000 people found that people with tooth loss who did not use dentures had a higher observed risk of cognitive impairment, while the association was much smaller among denture users. The researchers emphasized that these findings show an association, not proof that dentures prevent cognitive decline.

The evidence is intriguing, but cognition is only one part of the story.  Chewing appears to participate in a surprisingly large number of processes before we ever get around to thinking about what it might be doing for the brain.

Metabolic and Hormonal Effects of Chewing

Chewing helps prepare the digestive system for incoming food. The sight, smell, taste, and physical processing of food can initiate what is sometimes called the cephalic phase of digestion.  For instance, when you see or smell something delicious, and your stomach rumbles, or your mouth waters, that is the ‘cephalic phase’ of digestion.  Chewing stimulates saliva production and contributes to the mechanical preparation of food for swallowing and digestion.

And the more thoroughly food is chewed, the more thoroughly it is mixed with saliva and broken into smaller particles.  That matters.

A systematic review examining chewing and gastrointestinal and nutrition-related factors found evidence supporting several relationships between chewing and swallowing, gastrointestinal processes, and nutrition, although the authors rated the certainty of much of the evidence as low or very low. In other words, the basic biology makes sense, but we still have plenty to learn about how much chewing changes what happens farther down the digestive tract.

What we are actually eating is another thing, entirely.  Our gut microbiome is a factor, as well, and a fun fact to keep in mind is that what we eat affects our gut microbiome, and both what we eat and our gut microbiome affect both physical health and mental health.

Chewing also appears to influence appetite and satiety, which is ‘fullness’, or, the opposite of being hungry.  Research has found that oral processing—including the amount of chewing and the speed at which food is eaten—can affect food intake and subjective hunger.  Studies have also investigated changes in gut hormones associated with satiety.  The evidence is interesting, although researchers continue to work out exactly how these effects translate into long-term changes in eating behavior or body weight,

In other words, chewing isn’t simply something we do to food.  It is part of an entire process that affects our whole body.

Bone Health and Jaw Structure

Teeth, which we have decided are not optional, also play a structural role in maintaining the jaw.  The alveolar bone – the portion of the jawbone that directly holds and supports the teeth – is closely connected to the presence and function of the teeth.  Mechanical loading contributes to bone remodeling, and after a tooth is extracted, the surrounding alveolar ridge predictably changes shape and volume as the bone remodels.

That loss of bone can alter facial structure and make it more difficult to restore missing teeth with dentures or other prosthetic replacements.  It can also further affect chewing function, creating a rather unfortunate cycle:

Lose a tooth.  … Chewing changes.  … The surrounding bone changes.  … Chewing may become more difficult still.

This is one reason restoring missing teeth is about more than filling an empty space in a smile.  It is about restoring, as much as possible, a functioning mechanical system.

The Oral Microbiome and Systemic Health

Don’t forget the microbial world living inside our mouths.  The oral cavity contains a remarkably diverse ecosystem of microorganisms.  In a healthy mouth, these communities exist in a dynamic relationship with one another and with the tissues of the host.  When that balance is disrupted, as can occur with periodontal disease and other oral conditions, the resulting dysbiosis can contribute to local inflammation and may have consequences beyond the mouth.

Researchers have found associations between oral microbial disturbances/infections and a variety of systemic conditions, including cardiovascular disease, diabetes, respiratory disease, and some neurological and inflammatory disorders. Proposed mechanisms include systemic inflammation, immune interactions, and movement of microorganisms or microbial products beyond the oral cavity.

But this is another area where we need to be careful.  Association does not automatically mean causation, and researchers are still trying to determine which relationships are causal, which are bidirectional, and which may simply reflect shared risk factors.  I think we all already know that we don’t already know all that there is to know, and this is one of those areas.

Still, the basic point is fascinating:  The mouth is not a sterile container.  It is an ecosystem, and that ecosystem is not completely isolated from the rest of the body.

The Role of Dental Care in Preserving Mastication

If chewing is a biological function rather than simply a cosmetic convenience, then preserving the ability to chew deserves to be taken seriously.  Preventive dental care, early treatment of dental disease, and appropriate prosthodontic care when teeth are lost all have the potential to preserve or restore masticatory function.

Unfortunately, access to that care remains a significant problem for many people.  Financial barriers, inadequate insurance coverage, and geographic shortages can make it difficult or impossible for people to obtain timely treatment.  But there is something important to understand here: replacing a missing tooth is not necessarily about vanity.

Restoring teeth can mean restoring the ability to chew, and restoring chewing may mean restoring more than simply the ability to eat a steak.  Chewing affects what a person can eat, how they process food, how their jaw is mechanically stimulated, and potentially even some of the neurological activity associated with chewing.  That is a considerably bigger job description than “making a smile look nice.”

A Broader View of Oral Health

There is another question hiding here, too.  Medicine and dentistry developed as separate professions, and specialization has brought enormous benefits.  There is certainly value in having people devote their careers to understanding specific parts of the human body.  But, the more we learn about chewing, the harder it becomes to pretend that the mouth operates independently from the rest of us.

The nerves involved in chewing connect with the brain.  The food we chew enters the digestive system.  The forces generated by chewing affect the jawbone.  The organisms living in the mouth interact with the body’s immune system.

Perhaps there is a larger conversation to be had about how we divide the human body into specialties—and whether specialization can sometimes make it harder to see the whole person.  But that’s a discussion for another article.

Conclusion

We started this discussion with something that seems almost absurdly ordinary: chewing.  Or, if you prefer, mastication.

But chewing is not simply the process of making food small enough to swallow.  It engages the nervous system, contributes to digestion, participates in appetite and metabolic signaling, provides mechanical stimulation to the jaw, and takes place within a remarkably complex microbial ecosystem.

The research connecting mastication with cognitive health is especially intriguing, but it is only one piece of a much larger picture.  The more closely we look, the more difficult it becomes to separate “dental health” from health itself.  Teeth, which we have already established are not optional, are useful because we use them.  And what they do when we use them turns out to matter far beyond the mouth.

It is past time to start taking tooth loss seriously.

References

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• Sta Maria MT, Hasegawa Y, Khaing AMM, Salazar S, Ono T. The relationships between mastication and cognitive function: A systematic review and meta-analysis. Japanese Dental Science Review. 2023;59:375–388. doi:10.1016/j.jdsr.2023.10.001. PubMed
• Ma X, Zhang Y, Wang J, et al. Association between denture restoration for tooth loss and cognitive impairment: A systematic review and meta-analysis. Journal of Prosthodontic Research. 2025;69(3):313–320. doi:10.2186/jpr.JPR_D_24_00060. PubMed
• Kumar A, Almotairy N, Merzo JJ, et al. Chewing and its influence on swallowing, gastrointestinal and nutrition-related factors: A systematic review. Critical Reviews in Food Science and Nutrition. 2023;63(33):11987–12017. doi:10.1080/10408398.2022.2098245. PubMed
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