Coffee contains caffeine, a stimulant that boosts alertness and energy, and can also affect gut activity in various ways.

Stimulating bowel movements

Coffee can stimulate digestive tract muscles to contract, moving food and waste through the intestines. Caffeine contributes to stimulating bowel movements; however, decaf coffee (which has most caffeine removed) has a similar effect, suggesting other compounds in coffee may be involved in this process. According to Healthline, coffee's impact on the gut varies from person to person.

Coffee can also stimulate the hormones gastrin and cholecystokinin, which are linked to digestive tract activity. When food or drinks enter the stomach, the body can simultaneously activate a natural reflex that increases colon contractions, creating an urge to defecate. Therefore, the need to have a bowel movement after a morning cup of coffee is not necessarily an abnormal sign, but can result from a combination of caffeine, other compounds in coffee, the timing of consumption, and the gut's natural reflex.

Coffee can stimulate bowel movements, promoting defecation. *Photo: Bao Bao*

Potential changes to the gut microbiome

According to the Times of India, beyond its effect on bowel movements, coffee has also been studied for its potential to influence the microbiome, with trillions of microorganisms living in the digestive tract.

In 2024, scientists from the University of Trento (Italy) and international collaborators analyzed gut microbiome data from over 22,800 individuals in the US and UK, cross-referencing it with over 54,000 samples from other data sources. The results showed that coffee is linked to gut microbiome composition, notably an increase in the bacterium *Lawsonibacter asaccharolyticus*.

The amount of *L. asaccharolyticus* was significantly higher in coffee drinkers compared to non-drinkers. To verify this, the research team cultured the bacteria in a laboratory and added coffee. Both regular and decaf coffee promoted bacterial growth, indicating that this effect may not only stem from caffeine but also relate to other compounds in coffee.

Coffee contains many plant compounds such as polyphenols and chlorogenic acids. Gut bacteria metabolize these substances into other compounds, including quinic acid.

Not everyone finds coffee comfortable

In some individuals, coffee's stimulating effect on the gut can be stronger, causing frequent loose stools, abdominal pain, or discomfort.

Individuals with sensitive digestive systems, especially those prone to diarrhea, may experience more pronounced symptoms after drinking coffee. For people with irritable bowel syndrome (IBS), the reaction also depends on each case and symptom type.

Beyond coffee itself, ingredients added to the beverage can also affect the gut. Milk or cream containing lactose can cause bloating, cramps, or diarrhea in individuals with lactose intolerance. Therefore, if you frequently experience abdominal pain, diarrhea, or bloating after drinking coffee, you should monitor your body's reactions and the accompanying ingredients instead of assuming the cause is solely caffeine.

How to drink coffee without causing gut discomfort

Healthy individuals should drink moderate amounts and limit sugar and cream if they cause discomfort. Those prone to abdominal pain, diarrhea, or reflux can reduce their intake, try decaf varieties, or avoid drinking on an empty stomach. Coffee is not considered a treatment for constipation. If persistent diarrhea, abdominal pain, changes in bowel habits, or blood in the stool occur, individuals should seek medical examination to determine the cause.

*Bao Bao (Compiled)*