You might have heard the rumours as a kid: Swallow gum and it will sit stubbornly in your stomach for seven long years.
But what does science have to say about that? Reactions, a video series from the American Chemical Society, traced the steps taken by our body’s digestive system to find out that while some of the gum we chew can survive digestion, it "doesn’t mean the gum you swallowed in grade school is still there". Phew.
Turns out there are three basic components of digestion: The first includes the mechanical processes that are required to process your food when you first ingest it, i.e. chewing.
The second focuses on the enzymes or proteins in your saliva and stomach that help break down that food. Last but not least are acids, which dissolve what’s left into something your body can comfortably pass through your intestines.
Traditionally, when you eat, your teeth and tongue work together to munch the food into small bits. Then your muscle movements push the food through the digestive tract until it is emptied into the stomach and churned with digestive juices, as shown below:
While this is happening, the enzymes in your saliva, stomach juices, and intestines drive chemical processes that allow you to convert that food into nutrients your body can use.
Then, the acids in your stomach get to work, dissolving what’s left of that food into a mush that your body can comfortably pass through your intestines and, eventually… dispose of.
But gum isn’t designed to be smoothly digested by your body like regular food. That’s because it contains either a natural or synthetic rubber base, which is what gives it its gummy consistency. Butyl rubber, commonly used in gum (as well as tires and basketballs, mm!), is a synthetic rubber that provides it with an ideal chewiness.
You’ve probably noticed that gum is unaffected by the crushing of your teeth - that’s kind of the point. So when you swallow the gum, it moves through your digestive tract into your stomach as one giant wad.
While your enzymes are able to break down the carbohydrates, oils, and alcohols in the gum as they would with regular food, the rubber base in the gum is basically immune to these enzymes.
Even the 'harsh brew' of acids in your stomach is no match for this rubber base. (Remember that rubber is so resilient that we use it in gloves for protection.) As a result, part of your gum survives all of your digestive system’s attempts to break it down.
But so do parts of a lot of other things you eat, like sunflower seeds or corn. So while that gum you swallowed is rebellious enough to stand up to your digestive processes, that doesn’t stop your muscles from eventually ushering it through your body and out the other end within a couple days.
To learn more, check out Reaction’s video below:
This article was originally published by Business Insider.
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