The myth originated from many years of medical cases of mostly children who suffered digestive system problems after swallowing gum. Some of these cases have led to serious emergency problems, especially when lodged in the esophagus. The myth of gum remaining in the stomach for seven years is not true. But should serve as a warning about the dangers of swallowing gum and the problems it can cause. Especially in young children that continuously swallow gum. It is important not to give gum to children that are too young to understand the importance of not swallowing it.
Chewing gum has been around for thousands of years and how it is made has changed several times. Earlier gums were made using tree resin and were used for medical purposes. Gum today is a favorite candy by kids and adults. and is used to freshen breath and used to administer medicine such as nicotine gum.
Gum base is made today with a synthetic plastic and then flavored and colored. Our digestive system will digest the flavoring and sweeteners, but not the synthetic base. The synthetic base will pass with in a day or two through our intestines and out in our fecal waste.
Swallowed gum can get lodged in the esophagus and due to its sticky taffy like base, it is hard to remove. If other objects our swallowed at the same time; such as coins this can cause serious problems.
Medically there is no proof that gum does stay in the stomach for more than a couple of days. There have been many x-rays done of the stomach and with the amount of people who do swallow gum, their x-rays would show obstructions.
So to be on the safe side, do not swallow gum.