Coffee drinkers know that coffee helps keep the intestines moving, but Texas researchers are trying to figure out why this is true, and it does not seem to be about caffeine, according to a study presented at Digestive Disease Week® (DDW) 2019. Researchers, fed on coffee from rats and mixed with intestinal bacteria in Petri dishes, discovered that coffee suppresses bacteria and increases muscle motility, regardless of caffeine content.
"When the rats were treated with coffee for three days, the contraction capacity of the small bowel muscles seemed to increase," said Xuan-Zheng Shi, PhD, lead author of the study and a professor. Associate of Internal Medicine at the University of Texas Medical Branch, Galveston. "It's interesting to note that these effects are independent of caffeine, because caffeine-free coffee has had effects similar to those of regular coffee."
Coffee has long been known to increase bowel movements, but researchers have not clarified the reason or the mechanism. The researchers examined changes to bacteria when faeces were exposed to coffee in a petri dish, and studying the composition of faeces after the rats were ingested different concentrations of coffee for three days. The study also documented changes in the smooth muscles of the intestine and colon, as well as the response of these muscles when they are exposed directly to the coffee.
The study found that 1.5% growth of caffeine prevented the growth of bacteria and other microbes in the feces of a Petri dish, and that the growth of microbes was even lower with a coffee solution at 3%. Decaffeinated coffee had a similar effect on the microbiome.
After the rats were fed coffee for three days, the total number of bacteria in their feces was reduced, but researchers indicated that further research was needed to determine whether these changes favored firmicutes, considered "good" bacteria, or enterobacteria, considered negative.
The inferior bowel and colon muscles of rats showed increased ability to contract after a period of coffee ingestion and coffee stimulated contractions of the small intestine and colon when tissues muscles were exposed to coffee directly in the laboratory.
The results confirm the need for additional clinical research to determine whether coffee consumption could be an effective treatment for postoperative constipation, or ileus, in which the intestines stop functioning after abdominal surgery, said the authors.
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