Sir, chronic consumption of chewing gums sometimes causes side effects because too much xylitol has been known to draw too much water into the gut with it or it may get fermented in the gut by intestinal bacteria which results in nausea,bloating, diarrhea and a psychological feeling of dependence. Apart from these most of the chewing gum contains aspartame, which in the body is broken down to phenylalanine, few of the people have genetic abnormality to metabolise it. So it leads to phenylketonuria in them. This informations are usually mentioned in most of the chewing gum brands.