Why Does Your Stomach Growl?

If asked why their stomach growls, people may answer:

1. Because I’m hungry
2. I swallowed some air
3. Because my stomach is gassy
4. I am under stress
5. I have indigestion

But what is fact and what is fiction?

Your stomach may make noise when you’re hungry and lacking food in your stomach, but it can also growl when you’re not hungry and your stomach is full.

The growling noise may not even be coming from your stomach at all but rather from your small intestine. When your stomach or intestines makes noise, it is a phenomenon technically known as “borborygmi” and you may not hear it at all.

The noises are loudest when your stomach is empty, which is why they’re often associated with hunger.

What are the causes?

The rumbling sound is the result of muscular contractions, combined with the presence of liquids and gases. It’s a perfectly normal function and one that occurs most of the day.

Your intestines tend to quiet down when you’re sleeping but a complete absence of bowel sounds can actually be a sign of a medical emergency, especially if it’s accompanied by severe abdominal pain.

According to the International Foundation for Functional Gastrointestinal Disorders (IFFGD), here’s what’s really causing these sounds:

“Within the intestines, ingested fluids and solids are mixed with the daily secretion of about eight liters (two gallons) of enzyme-rich fluid, most of which is subsequently absorbed. However, fluid moving through a tube is silent – it is only when there is air in the pipes that we hear the plumbing.
In the intestine ever-present gases originate from swallowed air and the release of hydrogen, carbon dioxide, and other gases by the bacterial fermentation of undigested food in the lower gut. Even when inaudible to the intestines’ owner, characteristic sounds may be listened to by a doctor or nurse using a stethoscope.

While the noisy movement of fluid and gas occurs at all levels, the most audible sounds originate from the stomach. Whether audible or not, bowel sounds in the absence of other significant symptoms are normal phenomena of no medical significance.”

Growling Is Part of the Migrating Motor Complex (MMC):

If you hear your stomach growling, it’s likely because your stomach and intestines are engaged in a process called the migrating motor complex (MMC). This typically occurs when your stomach and intestines have been empty for about two hours.

Sensing the absence of food, receptors in the walls of your stomach cause waves of electrical activity in your enteric nervous system, which is like a second brain embedded in the wall of your gut.

This, in turn, triggers hunger contractions that travel the entire length of your gut, helping to clear out stomach contents, mucus, food particles, bacteria and other accumulated debris between your meals. A poorly functioning MMC has been linked to abdominal pain, nausea, vomiting and indigestion.

The hormone motilin is thought to be involved in triggering different phases of the MMC, but little is known about it because it’s not expressed in mice and rats and therefore hasn’t been widely studied, since mice and rats are the prime subjects for many studies.

What is known is that motilin levels increase cyclically every 90 to 120 minutes between meals and motilin release is halted after you eat a meal. When motilin levels peak, contractions of muscles in your stomach and intestines will also peak.

It’s thought motilin may play a role in both obesity and hunger.

Dr. Jan Tack, a professor of medicine who studies gastrointestinal disorders at Belgium’s University of Leuven, told TIME:

“‘We have shown that motilin-induced hunger signaling is altered in people experiencing unexplained weight loss and obesity,’ he says. Tack says a person’s motilin levels also seem to change after bariatric procedures like gastric bypass surgery. Motilin may also affect the ways you experience pleasure or a sense of reward after eating. All of this research is very new. But manipulating motilin and the resulting MMC response may eventually emerge as a novel way to treat obesity, dyspepsia and other gut-related health issues, Tack’s research suggests.”

When Are Bowel Sounds a Problem?

Most of the time, a noisy stomach is nothing to be concerned about. However, bowel sounds are known to increase if you have dyspepsia, irritable bowel syndrome, or if you’re having a bout of diarrhea, due to increased muscle contractions and accumulation of fluids and gases.

Malabsorption conditions, such as celiac disease or lactose intolerance may also lead to what’s known as hyperactive bowel sounds.

IFFGD explains: “… Reduced small intestinal levels of the enzyme needed to digest the milk sugar lactose, permits that sugar to reach the colon intact where it is fermented by colon bacteria.

These organisms release hydrogen and products that attract fluids into the gut and stimulate its contractions. These amplify the three conditions that produce abdominal sounds: gut movement, gas, and fluid.”

In the more rare event of a mechanical obstruction of your gut, bowel sounds may also increase. In this case, the contractions in your intestines attempt to move solids, liquids, air and gas through a narrowed intestine, leading to loud, often high-pitched noises.

If you’re experiencing an obstruction, the noises will be accompanied by severe abdominal pain and illness and emergency medical attention is needed.

Too Much Sugar Can Cause a Noisy Stomach:

If you find your stomach is embarrassingly noisy, it could be because you’re eating too much sugar, particularly fructose and sorbitol, which is found in fruits and also used as a sweetener in many sugar-free gums and candies.

Sugar is a preferred food source for fungi that can produce yeast infections and sinusitis, whereas healthy probiotic-rich foods like fermented vegetables boost populations of health-promoting bacteria, thereby disallowing potentially pathogenic colonies from taking over.

Optimizing your gut flora is actually one of the most important steps you can take for your health. Not only could it help normalize your weight and ward off diabetes, but it’s also a critical component for a well-functioning immune system, which is your primary defense against all sorts of disease.

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