Irritable bowel syndrome, or IBS, is a disorder that affects the colon, or large intestine. It commonly causes cramping, abdominal pain, bloating, gas, diarrhea, and constipation.1
Impact of coffee and caffeine on irritable bowel syndrome
Coffee stimulates the gastrointestinal tract to over activity. In people susceptible, coffee produces a laxative effect through stimulation of rectosigmoid motor activity. This can happen as soon as 4 minutes after drinking. This effect has also been found with decaffeinated coffee, proving that the laxative effect is not purely due to caffeine.
Coffee is also highly acidic, which irritates the intestines, and can stimulate the hyper secretion of gastric acids. Decaffeinated coffee has been shown to increase acidity more than just caffeine or regular coffee. Coffee tends to speed up the process of gastric emptying, which could result in highly acidic stomach contents passing too soon into the small intestine, causing discomfort and pain.
Another reason why caffeine can cause issues in those with IBS is due to its diuretic effect. As well as having a laxative effect, caffeine can cause constipation, due to its diuretic qualities causing the body to urinate more frequently, and becoming dehydrated. This leads to drier, harder stools that are difficult to pass.
Caffeine has also been found to interfere with gamma-aminobutyric acid metabolism. Gamma-aminobutyric acid, or GABA, is a neurotransmitter naturally produced in the brain and gastrointestinal tract. It is important in mood and stress management, as well as having a calming effect on the gastrointestinal tract. It has been discovered that caffeine interferes with the binding of GABA to GABA receptors, preventing it from carrying out its function effectively. In individuals with IBS, the gastrointestinal tract is already irritated and hyperactive, and the lack of GABA’s calming effect only worsens this problem. In addition to a direct effect on the gastrointestinal tract, GABA’s role in stress and mood management is also inhibited by caffeine, worsening IBS symptoms, since psychological stress is known to be a contributing factor in IBS.2