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BI Answers: Why does my stomach growl?
Whether you call it a growl, a rumble, or a gurgle, chances are you’ve experienced some noise coming from your stomach at an inopportune time, like in the middle of giving a presentation or taking a test.
Well, it turns out your stomach isn’t fully to blame, but also your small intestine. Also good to know: the growling sound is a natural part of your digestive system but is not necessarily related to hunger, although it can be.
The digestive system (abridged version)
Think of the digestive system as an enormous tube beginning with your mouth and ending with a trip to the bathroom — a long and winding trail that can be up to 30 feet long in adults.
In the simplest terms, each bite of food you take enters your mouth, travels down the esophagus and ends up in the stomach. The stomach churns up the food with digestive acids. It’s the small intestine that “digests the food with enzymes to absorb the nutrients — the good stuff — into your body,” Dr. Steven Moss, director of the Brown University Gastroenterology Fellowship Training Program, told Business Insider.
The system relies on a series of contractions known as peristalsis, which are essentially waves that push the churned up food (a combination of liquid, solid, and air) from the stomach into the small intestine and through the gastrointestinal system.
“Everybody has their own rhythm in peristalsis,” says Dr. Gary Luckman, a gastroenterologist at DigestiveCARE in Plantation, Florida and a member of the American Gastroenterological Association.
Each part of the gastrointestinal tract has a different number of approximate contractions per minute. “The stomach is classically three contractions per minute. The small intestine is 8-10 contractions per minute,” according to Moss.
Grumble, grumble, grumble
These contractions, which are part of the normal digestive process, can sometimes cause the noise that we think of as a stomach rumble.
“The peristalsis causes a contraction, squeezing the intestines, and it squeezes up against the air and the fluid, which causes the noise or the growling or the sensation,” Luckman says. He also pointed out that the person experiencing the rumbling sensation usually feels it and is more aware of the sound than the outside world.
The growling may be somewhat more pronounced if you’re hungry, but can actually occur at any time. As Dr. Laurence Bailen, a gastroenterologist at Newton-Wellesley Hospital explains in Tufts Now, “If you have food in your intestine, it can muffle the sound, but if you have air in there, and that’s all you’re moving, that is what you’ll hear.”
Growling versus gas
The experience of a stomach rumble is not related to the passing of gas as this is largely a function of the large intestine, or colon, during the next stage of the digestive process.
“Flatulence is when the gas comes out the bottom end — and that could be a result of food moving through the gastrointestinal tract,” says Moss. “But the growling comes from much higher up, it comes from the small intestine and sometimes from the stomach. They’re not necessarily the same thing, but both are a consequence that the gut is moving.”
Is there a way to stop the rumble?
It’s kind of a confusing idea, but your stomach is actually most active when it is empty.
“The function of the stomach is to grind up food, but when you take in a large meal it has to grind very slowly,” says Moss. “But once that has moved into the small intestine and the stomach is then empty again then it starts to move and expel any small particles. So paradoxically it moves more when it’s empty than when it’s full.”
So one way to stop the rumble is to put something in your stomach, but this is not foolproof, because your small intestine still makes noises if there is food in your stomach.
And when it comes to stomach and small intestine activity and giving a presentation or taking a test, the whole system may just go haywire, no matter if you’ve eaten or not. That’s because when your nervous, the activity of the gut increases.
“The tension is stimulating intestinal movement,” according to Moss, which is why some people have to go to the bathroom before giving a presentation, or your stomach does somersaults and makes all sorts of noises when nervous about a big date.
This post is part of a continuing series that answers all of your “why” questions related to science. Have your own question? Email [email protected] with the subject line “Q&A”; tweet your question to @BI_Science; or post to our Facebook page.
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