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NatureInterface > No.14 > P034-039 [Japanese]

Chewing Cures Dementia and Obesity!? Unlock the Misterious Relation between Mastication and Brain -- Shigeru Saito/Minoru Onozuka/Toshiie Sakata












Chewing can treat senile dementia and reduce fat!?

Clearing up the mysterious relationship between chewing and brain


Shigeru Saitoh

Former director of Japanese Society for Masticatory Science and Health Promotion

Minoru Onozuka

Professor of Kanagawa Dental College

Toshiie Sakata

Professor of Nakamura Gakuen University


In recent years, it has become clear that chewing has effects on health of the whole body. It has been reported that chewing can control the relaxation effect, stress relief, progress in memory, spatial recognition, and even metabolism of fat. The secret is in the relationship between chewing and brain.

Why Athletes Chew Gums?

Five years ago, at the world cup championship of soccer, Shoji Jo who played at forward position was blamed for chewing gum during the game. People said that his behavior was a bad manner. Jo and sports experts objected to this public opinion and insisted that chewing gums relaxed athletes. This news topic let a lot of people know such an effect of chewing gums. (But in his case, stress might have overpowered the effect of chewing gums and, he couldn°«t score in the game). After that, it became normal to see athletes and coaches chewing gums during games.

On the other hand, we often hear that the jaw of the modern people has retrograded because of the change of foods after the World War II. Some scientists say that one of the reasons of causing obesity and life-style diseases is eating soft foods like fast food and processed food. There seems to be something important to our health in the act of chewing.

Shigeru Saitoh, a former director of Japanese Society for Masticatory Science and Health Promotion, Minoru Onozuka, an associate professor of Gifu University School of Medicine, and Toshiie Sakata, Director of the Japanese Society of Pathophysiology and professor at Nakamura Gakuen University have done researches on the issue. In the research, chewing had great effects upon both dementia and obesity, which are great enemies to old people. Not only the effects of concentrating well and relaxing, the act of chewing also enhances memory, and accelerates metabolism of visceral fat.

How dose chewing help our health? Let°«s clear up the mechanism with their research findings.

The Reason why the Mouth of Penfield°«s Homunculus is So Big

Mr. Shigeru Saitoh, a former Director of Japanese Society for Masticatory Science and Health Promotion says, °»There is a reason why mouth is especially important in body. We have maps on our primary Somatosensory area of cerebral cortex, which is located closest to its surface. The map is called Homunculus (means dwarf) and shows body region areas. In this map of the brain, the areas related to lips, hands and fingers are comparatively large. As readers might know it is named °∆Penfield°«s Homunculus°«, which was developed by American neurophysiologist Dr. Wilder Penfield in 1950s in Canada. He developed a new surgical approach in which the patient suffering from epilepsy was given a local anesthetic and thus remains conscious for the operation upon their approval Penfield then removed the skullcap to expose the brain tissue of the patient. He gave electric stimulus to many areas on their cerebral cortexes, asking the patient to describe what she or he was feeling. The identified functions of the brain show the area related to lips in Somatosensory area is 30% of the whole Homunculus. Therefore, it means that chewing has great effects on the brain°….

Actually, mouth is a really sensitive organ that is able to sense even a hair. The functions of Mouth include not only chewing and swallowing foods but also tasting, speaking by moving tongue and lips, and making facial expressions. Mr. Saitoh points out that the reason for the large area related to mouth in Somatosensory area is that the amount of information input into mouth is larger than that for other sensory organs. °»In conclusion, eating is equal to living. We cannot live without eating. This explains that chewing releases stress. The reason is that in a world where the stronger prey upon the weaker like the wild animal, only the strong can manage to chew. That is to say, chewing is the proof of strength and living. In the recent research, it was found that chewing stimulates amygdala, which governs emotions and controls adrenalin that is secreted by stress. There is a scientific evidence for why athletes chew gums.

Also, chewing relates to remembrance, as people tend to remember the taste and sense of food on their tongue once they°«ve eaten it. For example, it is the well-known fact among medical professionals that elderly patients get senile dementia as soon as starting to receive parental nutrition or insertion of a tube. So, we directed our attention to the relationship between brain and chewing, especially the hippocampus, which administers remembrance and chewing°….

If we could find the close relationship between brain and chewing, we may be able to prevent senile dementia by stimulating and activating nerve cell of brain by chewing, which is physical stimulus. Mr. Saitoh suggested such a hypothesis.

If it were true, it would be happy news to patients with the possibility or early stage dementia. Moreover, due to the increasing of medical expenses for the elderly that is mainly attributed to senile dementia among other illnesses, chewing would be the most reasonable way of prevention against senile dementia, if it worked. Based on this concept, Mr. Saitoh immediately started to collaborate with Mr. Onozuka, who is the specialist of brain science at Gifu University.

A Mouse that cannot Chew easily Loses Way.

So what kind of experiment was done? Before mentioning about that, we asked Mr. Onozuka about the function of hippocampus.

°» Hippocampus is a small part as small as thumb located in the inner part of brain, but as it all information people receive goes through it, once destroyed, we are unable to manage and memorize things. In addition, hippocampus has another important function. It is spatial recognition. In short, hippocampus recognizes the positional relationship, for example, desk or chair. Therefore, when people get senile dementia and their brains atrophy, they lose memories or ways°….

It suggests that, hippocampus does not only govern memories but also take a very important part to realize positions of objects or ourselves.

Mr. Onozuka said, °» However, nobody can avoid the atrophy of hippocampus by aging. Regardless of having senile dementia or not, hippocampus becomes smaller. Once hippocampus becomes extremely thin like a paper, it causes senile dementia.

These days, the functions of hippocampus have been revealed like this, but when I first heard that Mr. Saitoh wanted to develop the relationship between senile dementia and chewing, I secretly doubted the relationship between chewing and hippocampus. However, when we started to research, we developed interesting facts one after another°….

At first, Mr. Onozuka monitored the behavior of three types of mice. The first mouse had its masseteric nerve cut, enabling it to chew, the second mouse had its teeth shaved so it couldn°«t chew well, and the third was a normal one. They were put in a tub with diameter of 90 cm filled with water. Their swimming paths were monitored and analyzed by CCD camera, which was set beyond the pool. In fact, there was a platform about 1 cm under the surface of water, and the key point of this experiment was to see if the mice could remember the place of the platform. Then, mice°«s swimming paths to the platform and the time taken were recorded everyday with changing places to leave the mice on the water.

On the first day, all the mice just swam in a circle and clung to the platform when they happened to find it. There were no particular changes. However, about a week later, while the mice that were able to chew became to reach the platform straightaway, the mouse that was unable to masticate still swam in a circle just to get out of the tub. As a result, it was realized from this experiment that the mouse that cannot chew are not able to memorize the position of the platform.

°»The reason why the mouse that was unable to chew did not memorize the position of itself was that chronic stress was put on the mouse by not masticating and then, decreased acetylcholine in the brain caused such a disability. In fact, one of the largest causes of decline of hippocampus°«s operation is stress. When animals get chronic stress, corticosterone, which is adrenal cortex hormone, is secreted. It is known that increase of this hormone causes the death of cells. These days, we know that cell death in the dentate gyrus at the entrance of hippocampus happens most frequently. (Mr. Onozuka)

Chewing Gums for Two Minutes Improve Memory!?

Next, how about human beings? °»As for human beings, of course we couldn°«t shave or pull teeth, so we tried to adopt the functional MRI method. This is the experiment of analyzing the brain before and after chewing gums by MRI (Magnetic Resonance Imaging). The subjects were separated into a young group and the elderly group. We chose the opposite way of the animal experiment. We tried to analyze the change of hippocampus affected by chewing°….

The result showed that chewing gums activated the cells of hippocampus. In addition, in the young group, chewing gums didn°«t leave any especial effect on memory, but in the case of the elderly, chewing gums improved not only hippocampus but also a lot of other regions of brain.

°» In the case of the young people°«s brain, where the basic activity level is high, chewing gums do not have a significant effect on the activity of nerves. On the other hand, in the case of old people, their basic activity level is not so high because of atrophy of hippocampus. Their hippocampus hardly takes any new information, so an association area, which works as a high-level unified transaction system placed just behind the forehead, helps hippocampus handle. I believe that chewing gums improved such active regions°….

In addition, Mr. Onozuka asked the monitors to see scenery to study the functions of hippocampus. The method is as follows. At first, subjects are asked to see pictures of familiar sceneries in order. Then, they are asked to rest for two minutes. After the rest, they are asked to see pictures including the ones shown previously and slightly different ones from those. Monitors then spot the pictures shown in the first round. The key point of this experiment is that during the first rest of two minutes, the subjects do not chew gums, but during the next two minutes, they chew gums. What kind of change in memory does this difference of condition make?

°» As expected, after chewing gums, all subjects got better memory. Actually, the data from MRI showed that before chewing, there was about 250 cubic centimeters area of hippocampus worked. After two minutes chewing, the active area was over 400 cubic centimeters. It means the increase of nerve activities°….

Mr. Onozuka did an additional experiment to apply this result to clinical practice. The method of the experiment was that old people as subjects were asked to 1) chew a lot 2) don°«t eat alone 3) eat what they want at least one dish. The subjects tried to do these three things for two weeks. Then, their hippocampus became to work better and their facial expression dramatically became lively. It proved that chewing could be an early preventive treatment for patients of the early stage or with potentials to have senile dementia. There is possibility of remedying the symptoms or preventing them.

Now, in NPO WIN, they are planning to develop °»Hippocampus Measuring System°…, which aims to diagnose early symptoms and possible patients of senile dementia with the leadership of Mr. Saitoh and Mr. Onozuka. The attempt to materialize the measuring spatial recognition by using 3D pictures and analyzing functions of hippocampus and frontal sinciput by tracking eye movements with wearable equipment has already started.

Cure obesity by chewing well.

The other important function of chewing is the operation of visceral fat decomposition. Mr. Toshiie Sakata at Nakamura Gakuen University clarified that chewing stimulates histamine nerve system inside the brain and makes visceral fat burn. °»Histamine is the substance, which affects the control of immune system and increase of this substance sharpens consciousness. When this happens, people °»wake up°…. Antihistamine makes us sleepy because it controls release of histamine. Recently, it was developed that chewing controls histamine nerve system. When chewing, the signal travels through mesencephalic trigeminal sensory nucleus (Me5) and motor tigeminal nucleus (Mo5). The signal for Me5 is carried to hypothalamus as histamine factory, histamines are mass-produced°….

The first approach Mr. Sakata took was depleting rats°« neuronal histamine in purpose of developing the relationship between Me5, where masticatory signal is carried in and the ventromedial hypothalamus (VMH) of saniety center. As a result, the group with the depletion of neuronal histamine of VMH increased the amount food of and eating time. On the other hand, the group with depletion of neuronal histamine of Me5 consumed the same quantity of food, but eating time was shorter. The finding indicates that brain neuronal histamine not only modulates satiation, but also controls the eating time.

In addition, histamine works on the nucleus of sympathetic nerve and accelerates the energy metabolism at periphery. °»Above all, histamine controls white adipose tissue (WAT) and decomposes fat. Not only that, when histamine nerve system is controlled, fat synthesis is also controlled at the gene level. In particular, the control of histamine nerve system decreases visceral fat, which is white fat and causes life-style diseases°….

In short, neuronal histamine, which is produced by mastication not only controls appetite, but also decomposes visceral fat and control its synthesis. At the same time, it maintains energy metabolism of living body by constantly promoting heat generation.

In the experiment at Mr. Sakata°«s lab, 25 subjects ate food after ten minutes of chewing gums and all them showed decreased appetite. We are currently conducting the same experiment on obese patients and the result of the preparatory experiments showed decrease in the patients°« visceral fat.

Obesity, which comes as the top of life-style diseases, can also be treated by chewing we do without intention in daily life. °»Eating by chewing well°…, which is taught as nothing unusual has deep meaning in fact. These reports show that the secret of health is found in our usual living.

Having started with the researches above, °»Vital care networks°… group in NPO WIN has just launched to develop the system of monitoring activity of sympathetic nerve or quantity of visceral fat using masseteric electromyography, and the system of finding early brain nerve diseases with a measuring system of spatial recognition (see page 28 / figure.5 to get the information about home health management system). Please look forward to our future activity.

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