Study finds what happens in your stomach when you drink coffee

20 May 2019

Image: © Photocreo Bednarek/

When it comes to helping your bowels move everything they need to, coffee is ideal, but it’s nothing to do with caffeine.

Anyone who has had a few cups of coffee in the morning will know of its ability to keep your bowels moving, but now researchers are trying to find out what exactly is behind this ability.

In a study presented as part of Digestive Disease Week, a team from the University of Texas Medical Branch fed rats a continuous diet of coffee, as well as mixing the liquid in with gut bacteria and petri dishes. Over time, the results showed that the drink suppressed bacteria and increased the bowels’ ability to keep everything moving but, interestingly, it also did so when it was decaffeinated.

“When rats were treated with coffee for three days, the ability of the muscles in the small intestine to contract appeared to increase,” said Xuan-Zheng Shi, lead author of the study. “Interestingly, these effects are caffeine-independent, because caffeine-free coffee had similar effects as regular coffee.”

The study found that growth of bacteria and other microbes in faecal matter in a petri dish was suppressed with a solution of 1.5pc coffee and was even lower at a concentration of 3pc. After the rats were fed coffee for three days, the overall bacteria count in their faeces decreased.

The team admitted that more research will need to be done to find out whether these changes are affecting ‘good’ bacteria – known as Firmicutes – or ‘bad’ bacteria called enterobacteria. Meanwhile, the study also found coffee made muscles in the intestine and colon smoother, increasing their ability to contract.

Shi and his research team are now looking to undertake more research to see whether drinking coffee might be an effective treatment for post-operation constipation, where a person’s intestines temporarily stop working after abdominal surgery.

This marks the second coffee-related discovery in as little as a week following the publication of a study that found those with a coffee addiction have a heightened ability to sniff out its aroma compared with non-coffee drinkers.

Colm Gorey was a senior journalist with Silicon Republic