Chewing gum can increase parasympathetic secretion, and since you are not allowed food, this can increase your
stomach acidity. This will not harm the colonoscopy procedure, but it could cause heartburns. The logic behind
keeping you on liquid diet is to avoid anything solid interfering in the procedure. If you chew the gum, then
keep the amount less and drink water after it. And yes, do not swallow! Take care and regards!