Chew your food; it could help protect you from illness.
The study, recently published in the journal Immunity, found that chewing food - otherwise known as mastication - can stimulate the release of T helper 17 (Th17) cells in the mouth.
Th17 cells form a part of the adaptive immune system, which uses specific antigens to defend against potentially harmful pathogens, while enduring "friendly" bacteria that can be beneficial to health.
According to the study team, led by Dr. Joanne Konkel of the University of Manchester in the United Kingdom, in the gut and the skin, Th17 cells are produced through the presence of friendly bacteria.
However, the researchers note that the mechanisms by which Th17 cells are produced in the mouth have been unclear.
Chewing 'can induce a protective immune response in our gums'
Dr. Konkel and colleagues note that the mechanical force required by mastication leads to physiological abrasion and damage in the mouth.
With this in mind, the team set out to investigate whether such damage might play a role in oral Th17 cell production.
The researchers came to their findings by feeding weaning mice soft-textured foods, which required less chewing, until they reached 24 weeks of age. At 24 weeks, the release of Th17 cells in the rodents' mouths was measured.
A significant reduction in oral Th17 cell production was noted, which the team speculated was down to a reduction in mastication-induced physiological damage.
Confirming their theory, the researchers found that increasing the levels of physiological damage in the rodents' mouths - by rubbing the oral cavity with a sterile cotton applicator - led to an increase in the production of Th17 cells.
Dr. Konkel and colleagues believe these findings indicate that chewing food may help to protect us from illness.
"The immune system performs a remarkable balancing act at barrier sites such as the skin, mouth and gut by fighting off harmful pathogens while tolerating the presence of normal friendly bacteria.
Our research shows that, unlike at other barriers, the mouth has a different way of stimulating Th17 cells: not by bacteria but by mastication. Therefore mastication can induce a protective immune response in our gums."
Dr. Joanne Konkel
The downsides of excessive mastication
However, the researchers caution that increased oral Th17 cell production may not always be beneficial; too many of these cells can increase the risk of periodontitis, or gum disease, which has been associated with numerous other health conditions, including diabetes and rheumatoid arthritis.
In their study, the team also found that long-term exposure to physiological damage caused by mastication can exacerbate the effects of periodontitis.
They came to this finding by feeding weaning mice hardened food pellets up until 24 weeks of age.
Compared with mice fed soft food, the mice fed hard food showed more mastication-induced physiological damage in their mouths and increased periodontal bone loss.
Still, the researchers believe that their findings could lead to new strategies to combat an array of illnesses.
"Importantly, because inflammation in the mouth is linked to development of diseases all around the body," says Dr. Konkel, "understanding the tissue-specific factors that regulate immunity at the oral barrier could eventually lead to new ways to treat multiple inflammatory conditions."