Does chewing gum stay in your stomach for seven years?

If you grew up in Britain, someone probably told you that if you swallowed your chewing gum it would stay in your stomach for seven years. It was a good way of stopping children swallowing gum. It was never true.

The short answer

Swallowed chewing gum does not stay in your stomach. It is true that your body cannot digest it, but that does not mean it hangs around. Like other things we cannot fully digest, it travels through the gut with the rest of your food and comes out the other end, usually within a day or two.

Why gum is indigestible

Most of a stick of gum is sweeteners, flavourings and softeners, and those dissolve in saliva while you chew. What is left is the gum base, the chewy part. In the United States the food regulator allows 46 different substances to be used in gum base, and today most gum bases are made from synthetic, petroleum based polymers, with natural ones like chicle now much less common.

Those polymers repel water, which is exactly why gum lasts so long in the mouth: saliva cannot break it down. The acid and enzymes in your stomach cannot break it down either. So the gum base is not digested, absorbed or used by the body. It simply passes through.

Indigestible is not the same as stuck

People tend to assume that anything the body cannot digest must get stuck. That is not how the gut works. It moves its contents along whether they can be digested or not, and plenty of fibre in ordinary food passes through undigested every day. A doctor writing for McGill University's Office for Science and Society points out that the average journey through the gut takes a little over 24 hours.

So where did the seven years come from?

Nobody knows. There is no study behind it, and experts who have looked for its origin say it is unclear and probably lost to history. It may simply have been a scary number chosen to make children think twice, and it worked for generations.

The grain of truth

There is one real, rare risk behind the warning. When a young child swallows lots of gum, day after day, it can clump together with other things in the gut and form a blockage. Reported cases involve children who swallowed several pieces a day over long periods. That is why the sensible advice stands: gum goes in the bin, and it is not for young children who might swallow it. For what to do if a child swallows gum, see what happens if you swallow chewing gum.

And one more thing

If swallowed gum stayed in the stomach for seven years, anyone who had ever swallowed a few pieces would be carrying a lump of it around. They are not. The myth fails the simplest test there is.

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