Coffee is a beloved drink of millions of people around the world. For many, it is a morning cup of joe.
While caffeine is a great energy booster, it may also stimulate the urge to poop. In fact, one study found that 29% of participants needed to use the bathroom within twenty minutes of drinking a cup of coffee.
But why this happens?
In the search for the appropriated answer, scientists in Texas fed rats coffee with gut bacteria in Petri dishes. They found that coffee suppressed bacteria and increased muscle motility, regardless of caffeine content.
Scientists additionally examined changes to bacteria when the fecal matter was exposed to coffee in a petri dish, and by studying the composition of feces after rats ingested differing concentrations of coffee over three days. The study also documented changes to smooth muscles in the intestine and colon, and the response of those muscles when exposed directly to coffee.
The study found that growth of bacteria and other microbes in fecal matter in a petri dish was suppressed with a solution of 1.5 percent coffee, and growth of microbes was even lower with a 3 percent solution of coffee. Decaffeinated coffee had a similar effect on the microbiome.
Xuan-Zheng Shi, Ph.D., lead author of the study and associate professor in internal medicine at the University of Texas Medical Branch, Galveston said, “When rats were treated with coffee for three days, the ability of the muscles in the small intestine to contract appeared to increase. Interestingly, these effects are caffeine-independent, because caffeine-free coffee had similar effects as regular coffee.”
After the rats were fed coffee for three days, the overall bacteria counts in their feces were decreased. According to scientists, further study is required to determine whether these changes favor firmicutes, considered “good” bacteria, or enterobacteria, which are regarded as negative.
Muscles in the lower intestines and colons of the rats showed increased ability to contract after a period of coffee ingestion, and coffee stimulated contractions of the small intestine and colon when muscle tissues were exposed to coffee directly in the lab.