Most of us are aware that gum chewing is for mouth freshening or may be activity for the gums. Scientists are constantly finding new ways that gum can benefit us and one would be very surprised with the results. Studies show that gum chewing is can help fight the development of cavities by stimulating the production of acid-neutralizing saliva. Xylitol, a common gum ingredient, has been shown to have more specific cavity-fighting properties, as well. It can also, as noted above, help to fight bad breath. In addition to replacing vitamin pills and supplements, some doctors are considering gum as an alternative to pill-forms of prescription medicines because they would make medicine so easy to take. Gum is significantly featured in areas of weight-loss research, as well. Some state that the act of chewing helps them to control their hunger, while others rely on the freshness of strongly-flavoured mint gums to put them off of eating other foods.

Besides from these benefits, one more one study has shown that chewing improves memory function by increasing the flow of blood and hence the amount of oxygen to the brain. So the next time your teacher tells you to spit out a chewing gum you can explain the various benefits it has, but please avoid sticking the gum underside your desk.
Source