The Science of Gut Rumbles
Whoo, that was embarrassing. I accidentally let my borborygmi go. Of course, borborygmi is involuntary, I can’t help it. Borborygmi, the rumbling sound of your gut, doesn’t come from your stomach, nor is it solely because you’re hungry.
Borborygmi comes from your small intestine, the organ responsible for getting all the nutrients and macromolecules from the food you eat, which is in the form of a gooey mass called chyme. Your small intestine must move this partially digested lump of what was once food farther down to continue digesting. It does this by contracting the muscles behind the chyme while relaxing and opening the muscles in front of it. That push is called peristalsis, and it’s kind of like squeezing the bottom of a tube of toothpaste and rolling it up to get the last of the toothpaste out. Peristalsis is also what happens when you swallow your food.
Back to that goopy paste called chyme. Chyme has a lot of gas trapped in it, mostly from the digestion process. As the intestine moves the chyme down, the gasses are released and bubble around. Even when these bubbles aren’t very audible, you can still feel them as they interact with the nerves in your intestine.
Peristaltic movements aren’t a once per meal occurrence. It happens whenever the intestine needs to move the chyme to a new area for continued digestion. The movement could be as short as a few inches, but in the case of those really long and awkward gurgles, the chyme can move a few feet!
The movements aren’t tied to hunger, only to digestion. So why does it seem like we only hear the rumbles when we are ready to eat again? Those rumbles happen a lot, but when your stomach and intestines are filled with food and chyme, the sound is muffled and absorbed. When they’re empty, the moving gasses are amplified, like an echo chamber. Of course, there’s probably a psychological connection of hearing the rumble, then feeling hungry, rather than the other way around.
So what happens to that bubbling gas when it reaches the end of your small intestine? Well, it enters the large intestine and mixes with sulfurous gases. I don’t think I need to tell you how it ends.