Why Does Coffee Make You Poop? What Science Says

If your morning coffee sends you to the bathroom, you are far from alone, and there is nothing wrong with you. Why does coffee make you poop? In short, coffee can stimulate the muscles of the colon within minutes, likely through gut hormones and nerve reflexes rather than caffeine alone. That is why decaf can have the same effect.

Not everyone reacts, though. In a classic study, about three in ten healthy young adults said coffee gave them the urge to go. Here is what researchers have measured, the leading explanations, and when a change in bowel habits is worth a chat with your doctor.

Key takeaways

• In a 1990 study of 99 healthy volunteers, 29% said coffee made them want to have a bowel movement.
• In people who reacted, colon activity rose within about four minutes of drinking coffee, with regular and decaf coffee alike.
• Coffee stimulates gut hormones such as gastrin and cholecystokinin, which help coordinate digestion.
• Caffeine probably adds to the effect but is not the whole story.
• Persistent changes in bowel habits, blood, pain or weight loss should be checked by a doctor.

How many people does it affect?

The most cited data come from a 1990 study in the journal Gut by Brown, Cann and Read. They surveyed 99 healthy volunteers aged 17 to 27:

• 29% reported that coffee made them want to defecate.
• Women made up 63% of that group, a larger share than their share of the volunteers.

That is a small and young sample from more than 30 years ago, so the exact percentage should not be taken as a universal figure. But it fits everyday experience: coffee clearly has this effect on a sizable minority, not everyone.

What happens in the gut

The colon wakes up within minutes

In the same study, researchers measured pressure activity in the lower colon (the rectosigmoid) of 14 volunteers. In those who reported the coffee urge, activity increased within four minutes of drinking coffee and lasted at least 30 minutes. Hot water had no such effect. People who did not report the urge showed no increase.

Four minutes is far too quick for coffee to have reached the colon. That points to a reflex: something in the stomach or upper gut signals the colon to start moving.

Comparing coffee with water, decaf and a meal

A 1998 study by Rao and colleagues in the European Journal of Gastroenterology and Hepatology measured colon activity in 12 healthy adults over 10 hours after different drinks:

So a cup of regular coffee stimulated the colon about as much as a large meal, in this small study.

Why coffee does it: the leading explanations

1. The gastrocolic reflex

When food or drink enters the stomach, the body triggers waves of muscle activity in the colon to make room. This gastrocolic reflex is a normal part of digestion and tends to be strongest in the morning and after meals. Coffee seems to be an especially effective trigger, and morning coffee arrives exactly when the reflex is already primed.

2. Gut hormones

A 2022 review in Nutrients by Astrid Nehlig, covering about 194 publications, summarized evidence that coffee stimulates the release of gastrin, a hormone that increases stomach acid and gut movement, and cholecystokinin (CCK), which triggers bile release and is involved in coordinating digestion. Both may help set the colon in motion. Note that the review was supported by the Institute for Scientific Information on Coffee, an industry-funded body.

3. Caffeine, plus other compounds

Caffeine is a stimulant and may strengthen the effect, which fits the Rao study’s finding that regular coffee tended to act more strongly than decaf. But because decaf still works in many people, other substances in coffee, such as chlorogenic acids and other compounds formed in roasting, are thought to contribute. Scientists have not pinned down a single culprit.

4. Warmth, routine and habit

A warm drink, a regular morning routine and simply sitting down after waking may all play a role, though warm water alone did not stimulate the colon in the 1990 study.

Why some people feel it and others do not

Researchers do not fully know. Possible factors include individual gut sensitivity, hormones, habitual intake and timing. In the 1990 survey, women were overrepresented among responders. People with irritable bowel syndrome (IBS) may notice stronger effects; some find coffee a trigger for symptoms.

Practical tips

• Want the effect? Coffee with or shortly after breakfast, plus fiber and fluids, works with your natural morning reflex.
• Want to avoid surprises on the commute? Have your coffee earlier, or at the office rather than before leaving.
• Sensitive stomach? Try a smaller cup, drink it with food, or notice whether milk or sweeteners play a role, since lactose and some sugar alcohols have their own effects.
• Decaf is not a guaranteed fix. It may be milder for some people, but it can still trigger the reflex.

When to talk to a doctor

A coffee-related bathroom trip is normal. See a doctor if you notice:

• A lasting change in your usual bowel habits, especially if you are over 50.
• Blood in your stool or black, tarry stools.
• Ongoing diarrhea, abdominal pain or bloating.
• Unexplained weight loss or fatigue.
• Waking at night to have a bowel movement.

These symptoms are not caused by your coffee habit, but they deserve proper attention.

If you love the ritual but want less caffeine

Some people simply prefer a gentler, lower-caffeine morning cup or an espresso after dinner. Our Decaf Espresso is water-process decaf roasted dark, rich and chocolatey with a full body, and our Half Caf blends regular coffee with water-process decaf for half the caffeine. Both are roasted 1–5 days before delivery.

Coffee and digestion FAQ

Is it normal that coffee makes me poop?

Yes. Studies suggest a sizable minority of people experience it. It reflects normal gut reflexes and hormones.

Does decaf coffee make you poop too?

It can. In a 1990 study, decaf increased colon activity just like regular coffee in people who were sensitive. In another study, decaf’s effect tended to be a little weaker.

Why does coffee make me poop so fast?

The colon can respond within about four minutes, long before coffee reaches it. That suggests a reflex triggered from the stomach and upper gut, likely involving hormones like gastrin.

Is coffee a laxative?

Not in the formal sense, but it can stimulate colon activity in some people about as much as a large meal. If you have chronic constipation or diarrhea, talk to your doctor rather than relying on coffee.

Sources

1. Effect of coffee on distal colon function, Brown, Cann and Read, Gut, 1990.
2. Is coffee a colonic stimulant?, Rao et al., European Journal of Gastroenterology and Hepatology, 1998.
3. Effects of coffee on the gastro-intestinal tract: a narrative review and literature update, Nehlig, Nutrients, 2022.
4. Bowel cancer symptoms, NHS.

Facts checked in October 2026.

This article is for general information only and is not medical advice. If you have a health condition, are pregnant or take medication, ask your doctor before changing your caffeine intake.

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