We are what we eat, but the way we eat it might have a say in the matter, too. Scientists in the UK studying the immune system in mice have found that chewing can stimulate cells called Th17 in the mouth, in turn providing more robust protection against the harmful pathogens that cause illness.

Th17 cells play an infection-fighting role in other parts of the body like the stomach and skin by recruiting white blood cells to take up the fight. It does so after receiving the signal to attack from friendly bacteria, and it was thought that the same process was at play in the mouth.

But what scientists at the University of Manchester have found, is that things seems to work a little bit differently up top. The team discovered that during the act of chewing, abrasions induce a chemical called interleukin-6 from the gum tissue, which in turn boosts the numbers of Th17 cells.

"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," says lead researcher Joanne Konkel, "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."

For their study, the scientists demonstrated that they could stimulate higher amounts of Th17 cells in mice simply by altering the hardness of their food.

But before you go loading up on chewing gum, higher levels of Th17 aren't always good news. Excessive numbers of TH17 cells can contribute to periodontitis, a serious gum infection that eats away at the soft tissue and the supporting bone structure of the teeth. It can also increase chances of heart attack and stroke.

As another side effect, the team found that the extra damage caused by the chewing could exacerbate bone loss in periodontitis. The upside of this new knowledge, however, is that if it translates to humans, it could lead to new ways to manage certain conditions.

"Importantly, because inflammation in the mouth is linked to development of diseases all around the body understanding the tissue-specific factors that regulate immunity at the oral barrier could eventually lead to new ways to treat multiple inflammatory condition," says Konkel.

The research was published in the journal Immunity.