Stomach growling

[Lakewood]

Why causes your stomach to growl when you're hungry?

[Octavius]

In humans, the stomach is a highly acidic environment (maintained at pH 1.5 - 2 by the secretion of hydrochloric acid) with peptidase digestive enzymes, primarily pepsin. Pepsinogen is secreted by chief cells of the stomach and the acidic environment activates pepsinogen to form pepsin. The stomach's interior can secrete 2 to 3 litres of gastric fluid per day.

Though stomach growling is commonly heard and associated with hunger and an absence of food in the stomach, it can occur at any time, on an empty or full stomach. Furthermore, growling doesn't only come from the stomach but, just as often, can be heard coming from the small intestines. Growling is more commonly associated with hunger because it is typically louder when the stomach and intestines are empty and so the organs contents don't muffle the noise.

In general, the gastrointestinal tract is a hollow tube that runs from mouth to anus and its walls are primarily composed of layers of smooth muscle. When the walls are activated and squeeze the tract's contents to mix and propel food, gas and fluids through the stomach and small intestines, it generates a rumbling noise.

With all that going on, it's no wonder there is a bit of groaning really.