Coffee helps develop healthy gut microbes and aids bowel movements

By Dr. Ananya Mandal, MDMay 20 2019

There has been anecdotal evidence that coffee drinkers swear by their morning cup for normal morning bowel movements. A new study from researchers in Texas has shown that coffee indeed helps in bowel movements and also improves the gut microbe population. The study was presented at the Digestive Disease Week® (DDW) 2019 by the researchers. Notable finding of this study was the effects of coffee on gut bacteria as well as on bowel movements are not associated with caffeine content of the beverage.

Xuan-Zheng Shi, lead author of the study and associate professor in internal medicine at the University of Texas Medical Branch, Galveston, explained that the team fed rats coffee and tested the effects on the gut bacteria in petri dishes. He said, “When rats were treated with coffee for three days, the ability of the muscles in the small intestine to contract appeared to increase. He added, “Interestingly, these effects are caffeine-independent, because caffeine-free coffee had similar effects as regular coffee.” At the presentation, Dr. Shi presented the data for the abstract number Su1625 yesterday (19th May 2019). The study was titled, “In vivo and in vitro effects of coffee on gut microbiota and smooth muscle contractility in rats.”

Coffee helps develop healthy gut microbes and aid bowel movements . Image Credit: baranq / Shutterstock

They authors write that the mechanism behind these effects of coffee on the gut was known earlier but not explained at the molecular level. They noted that after feeding the rats with coffee for three consecutive days there were changes in the smooth muscles of the intestines and colon of the rats. These were directly exposed to the coffee.

Results of the study revealed that growth of bacteria in the fecal matter of the rat guts were stopped by using a solution of 1.5 percent coffee. When a 3 percent solution of coffee was used, the microbe concentration was even lower. Same effect was seen when decaffeinated coffee was used on the gut microbes, the researchers noted.

The team looked at the type of bacteria that coffee reduced in the rat faeces. While the need was to reduce harmful bacteria like Enterobacteria, healthy gut microbes needed to be augmented. The team also witnessed that after a period of coffee ingestion the gut muscles of the small intestine and colon started contracting. They exposed the tissues in the petri dish to coffee directly and found that coffee could stimulate the muscles.

Researchers suggest that further research with human volunteers to see if coffee could help patients who have paralytic ileus after an abdominal surgery. Paralytic ileus is a condition where there is sluggish movement of the gut muscles after an abdominal surgery that leads to constipation.

First author of the study Shrilakshmi Hegde and colleagues published their findings in the latest issue of Gastroenterology in its supplement. They had prepared the coffee solution by dissolving 100% Arabica coffee powder in hot water. The solution was then centrifuged and filtered. They used the faecal contents of the rats in petri dishes with agar containing 1.5 percent to 3 percent coffee. After 24 hours bacterial colonies and their growths were counted. This was part of their in vitro experiments. In their in vivo experiments the rats were administered 250mg of coffee in 2ml daily for 3 days. At the end of the experiment the performance of the gut smooth muscles when exposed to coffee was seen. Authors concluded, “in vitro and in vivo studies show that coffee stimulates intestinal smooth muscle contractility and inhibits gut microbiota in a caffeine independent manner.”

Contradictory findings – Coffee and gut microbes

Authors Kazuchika Nishitsuji and colleagues published a recent article (November 2018) in the journal Scientific Reports titled “Effect of coffee or coffee components on gut microbiome and short-chain fatty acids in a mouse model of metabolic syndrome.” This team also looked at the effects of coffee intake on gut microbes of obese lab mice. They also looked at the effects of coffee on liver pathology of these mice. They used coffee in the mice for 16 weeks and at the end found that it helped reduce liver inflammation in the lab mice. The coffee however did not alter the gram positive and negative bacteria in the guts of the bacteria. This team also collected faecal samples of the mice and analysed them for bacterial populations. They noted that altered gut flora of bacteria was not corrected by coffee intake.

Effect of caffeine of post-operative paralytic ileus

Greek researchers also looked at the effects of caffeine on post operative paralytic ileus. Their study was published in January this year in the journal Digestive Surgery. The team looked at studies that have been published looking at the effects of coffee on paralytic ileus. They found four studies suitable for their analysis where a total of 341 patients were included.

Results from meta-analysis of all the studies showed that when patients were administered coffee after the surgery the time taken for first bowel movement, first passage of flatus and tolerance to solid diet was significantly reduced. Authors concluded, “Even though the mechanism of action of coffee is not fully known, currently available literature demonstrates a significant improvement in gastrointestinal motility without having any impact on postoperative morbidity.

Coffee promotes healthy gut microbes

Authors S Perez Burillo and colleagues from Universidad de Granada, Spain published a study in the Journal of Agricultural and Food Chemistry this year in March. Their study was titled, “Spent Coffee Grounds Extract, Rich in Mannooligosaccharides, Promotes a Healthier Gut Microbial Community in a Dose-Dependent Manner.” The team writes that coffee is one of the “most consumed beverages around the world” and this consumption leads to a massive production of “spent coffee grounds” that lead to environmental problems. The team extracted mannooligosaccharides (MOS) from spent coffee grounds. They then used these to ferment with human feces samples. Results prevealed that these MOS from coffee had a prebiotic effect and stimulated growth of healthy gut bacteria such as “Barnesiella, Odoribacter, Coprococcus, Butyricicoccus, Intestinimonas, Pseudoflavonifractor, and Veillonella.” This benefit rose with dose of the MOS used from coffee grounds.