Many of you will have faced this all-too familiar embarrassment when out in public. But surprisingly, research shows that your stomach’s growls don’t necessarily mean you’re hungry, and nor does the sound always come from the stomach.
The reason we can often hear rumbling noises (scientifically known as ‘borborygmi’) is due to activity within the soft muscles of the stomach and small intestine. When peristalsis occurs, a process that churns and pushes food down the gastrointestinal tract using muscular contractions, the growling noise is initiated. The enteric nervous system (located within the gut) gives rise to fluctuations of electrical potential known as ‘Basic Electrical Rhythm’ (BER). These electric rhythms, though slower than the contractions of the heart’s cardiac muscles, allow the small intestine and stomach to carry out peristalsis. The small intestine produces 12 rhythms per minute, a rate four times higher than the stomach.
From this we can explain why the stomach growls even when we’re full. However, as we already know, these are still heard on an empty stomach. The reason these noises are intensified when we’re hungry is due to the lack of contents (ie. food and fluids) within our system to subdue out the sound. The enteric nervous system is at work once again when receptors signal to the brain the lack of food within our system; electrical waves known as ‘migrating myoelectric complexes’ (MMCs) are generated and this time, they lead to hunger contractions. This clever process searches and clears out the whole of the gut for any remaining food particles, mucus or bacteria accumulated within an area. Furthermore, the hormone Motilin may have a play in this. When we have low blood sugar (around 2 hours after eating), our intestines start to send signals that it is not getting enough nutrients to function.
The solution? To fill our stomachs! Unfortunately the way we eat can also have an impact on our stomach’s growling schedule. Eating too quickly, talking whilst eating or drinking water whilst exercising can lead to too much air being swallowed. This excess air loiters around in the small intestine, adding to the obnoxious sound already being sung out by our stomachs (as well as causing flatulence!). But once we satisfy our stomachs, the digestive muscles can refocus their energy from squeezing and pushing the air pockets around to breaking down food. Therefore, it is always advisable to eat slowly to minimise the amount of air being swallowed.
Hopefully that answered any questions about why our stomachs rumble. Hope you enjoyed, and please rate and comment below!