By Dr. Mercola
If asked why your stomach growls, many people would answer, “Because I’m hungry!” This is somewhat of a myth, however. 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 intestines. Oftentimes, when your stomach (or bowel) makes noise, a phenomenon technically known as “borborygmi,” 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 Causes Stomach Grumbling?
The rumbling sound in your stomach is the result of muscular contractions of your intestinal wall combined with the presence of liquid and gas. 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 your noisy tummy:1
“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).2
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.3
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…