People have been chewing gum in one form or another since the Stone Age, and for just as long, we’ve been spitting it out. But is all that expectorating really necessary? What happens to our bodies when we swallow gum? As with so many physiological processes, it’s complicated—as you can see in the video below from the American Chemical Society.

Gum is a funny thing. We chew it like food, and with added sugars and flavoring it tastes like food. But it isn’t food, and it never has been. It’s not even candy, since candy gets swallowed. It’s just gum. The first gums were made of stretchy and sticky natural tars. Then we moved on to tree sap, like that of the rubber tree, and today most gums are made with synthetic rubber. But all these ingredients, natural and synthetic, have something in common: we can’t digest them. Our bodies do not make any chemicals that can break down the polymers that make gum what it is.

So no, we can’t digest it. But that doesn’t mean it stays in our bodies. As lumps of mushed-up food are pushed through your digestive tract, your body breaks much of it down and takes out the nutrients it needs. The stuff that’s left over—including gum—will typically just be pooped out.

Does that mean it’s safe to swallow your gum? Yes and no. Accidentally gulping down a single piece shouldn’t do any harm to an adult’s body. But swallowing lots of gum can cause blockages in the digestive tract, especially in children, who are both smaller and way more likely to swallow their gum. This can lead to serious, painful constipation, sometimes requiring a doctor’s help. One case study described the removal of a toddler's gum blockage as “taffy-pulling.”

Let that be a warning.