I work with our youth group. Last week our pastor visited and gave a good talk on the Mass. The only thing I disagreed with him was when he said that “chewing gum” technically broke a person’s fast before Communion. But I did not challenge him at the time. In the past, I have seen this question answered here on Catholic Answers, and they said that “chewing gum” did not break a person’s Communion fast.
Chewing gum is among those things that are placed in the mouth but are not food. Other examples include chewing tobacco, breath mints, cough drops, toothpaste, and mouthwash. Even if some portion of one of these things – or its juices – is swallowed, it does not break the fast because it is not food.
Even so, as a matter of prudential judgment, it is a good idea to refrain from using such things in church because to do so can be, in some cases, impolite and cause scandal.