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What happens when you swallow chewing gum?

You may be able to walk and chew gum at the same time, but what happens if you happen to swallow the chewie stuff? Dr Karl has some answers.

We humans have been chewing gum for thousands of years, with very few side effects. Even so, many of us believe that if we swallow chewing gum, it will sit, undigested, in the gut for seven years.

My suspicions were immediately raised by the use of that nice prime number, seven, which pops in the motivational books and programs that offer you Seven Steps to a New and Improved You.

Archaeologists have found 9000-year-old lumps of black tar, with bite impressions suggesting that most of the chewers were kids aged 6 to 15. Two thousand years ago, the Greeks chewed the pale yellow resin from the mastic tree, while American Indians chewed spruce gum.

Chewing gum came to modern America via the Mexican General, Antonio Lopez de Santa Anna, who was responsible for the massacre at the Alamo, in San Antonio, in Texas. Santa Anna later entered the USA, and settled in Staten Island, New York. He brought with him a big lump of "chicle", the dried milky sap or latex of the Mexican sapodilla tree, which Mexicans had chewed for thousands of years.

A local New York inventor, Thomas Adams, tried unsuccessfully to turn it into a cheap rubber - but then he remembered how his son and Santa Anna loved to chew chicle together. In February 1871, small tasteless balls of chicle were first sold in New Jersey as "Adams New York Gum - Snapping and Stretching".

One of the nice side effects of chewing gum is that you increase the production of saliva, which is usually good for oral hygiene and your breath. The bad (and relatively uncommon) side effects include diarrhoea, tummy pain and flatulence (from the sorbitol in "sugarless" gum), mouth ulcers (from cinnamon flavouring), high blood pressure and low blood potassium (from liquorice flavouring) and higher blood mercury levels (from dental amalgam already in your mouth, but only in cases of excessive chewing).

Other unpleasant side effects include mechanical injury to the teeth, overuse injury (including temporomandibular joint syndrome) and even extrusion of dental repairs. But the overwhelming majority of us chew happily gum with no harmful side effects whatsoever.

Mind you, chewing gum in public places has given us the word "gumfitti", referring to gum pollution in public places. Gumfitti has created a whole new expensive industry involving fancy gum-removal devices (solvents, liquid nitrogen, etc). Singapore has even made most non-medical uses of chewing gum illegal.

Modern chewing gum has five basic ingredients. First is the gum base (the chewy bit which today is usually a mix of natural and synthetic gums). The other five ingredients are softeners (such as vegetable oils), flavours, sweeteners and corn syrup. Your mouth's saliva will dissolve all of these - except for the gum. So does the gum stick to the wet and slippery lining of your gut? Nope, it comes out with the rest of your solid wastes - through the same pathway, and almost always, right on schedule.

However, we humans are a very varied bunch, and you might expect that in the occasional human, chewing gum might get trapped. After a very exhaustive search, I tracked down the paper, "Chewing Gum Bezoars of the Gastrointestinal Tract", by Dr David Milov and his colleagues, in the journal Paediatrics.

He discussed three of his patients (aged 1 1/2 to 4 1/2) who had actually developed obstruction of the gut because they swallowed gum. However, the 1 1/2-year-old, who was a regular user and swallower of gum had also swallowed four coins. The other two children had a long history of swallowing gum, just to get another piece - up to seven pieces per day.

Dr Milov noted that the "rectal masses" had to be manually removed, and that they displayed the characteristic "taffy-pull sign" - a long multi-coloured skinny trail of gum, as the doctor pulled out a small lump of the mass.

But there are only a handful of these cases in the medical literature, and only in young kids (so you can forget the myth of the gum staying in the gut for seven years) and usually in kids that had a previous history of constipation or poor digestion that existed long before they started swallowing huge quantities of chewing gum.

The rest of us - we can chew walk and gum at the same time, and we can occasionally swallow it with no problems at all.

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