There's a ritual that unites millions of people every morning: wake up, have a cup of coffee… and run to the bathroom. Coincidence? Definitely not. For many, coffee is much more than a boost for the brain: it's also a direct impulse for the gut. A sort of gastrointestinal "call of the wild" that doesn't forgive delays.
But why does it happen? Is it the caffeine? Is it the moka pot's fault? Science actually has a lot to say about this effect: and the curious thing is that it happens especially in the morning, just when the whole world is still trying to remember how to dress. If you, too, can't drink coffee without having a mental map of the nearest bathroom, know that you're not alone—and, no, it's not all in your head.
Let's see why coffee stimulates the intestines, why it does so more powerfully in the morning, and how this little daily miracle of metabolism works. Spoiler: caffeine doesn't work alone, and habit plays a bigger role than you think.
Coffee's Laxative of Coffee
Not everyone reacts the same way to coffee. About 30-40% of people experience a significant laxative effect, while others experience minimal or no effect. It depends on various factors: individual sensitivity, gut microbiota composition, general diet, and drinking habits.
- Stimulating effect on intestinal motility. Caffeine is a central nervous system stimulant. It can increase intestinal peristalsis, the muscular contractions that push intestinal contents outward. This effect has also been observed with decaffeinated coffee, suggesting that other compounds in coffee (besides caffeine) contribute to this effect.
- Increased gastrin production. Coffee stimulates the secretion of gastrin, a hormone produced by the stomach that increases intestinal activity and acid secretion. This also helps stimulate the intestines.
- Stimulation of the gastrocolic reflex. After eating (or drinking coffee), a reflex called the gastrocolic reflex is activated, which signals the intestine to prepare to eliminate waste to make room for new food. Coffee can intensify this reflex, especially in sensitive individuals.
- Bioactive compounds in coffee. Coffee contains hundreds of chemical compounds, some of which (such as chlorogenic acids) may contribute to gastrointestinal stimulation.
Why Especially in the Morning?
Coffee tends to have a more pronounced effect on the gut in the morning for a number of reasons related to the way our bodies function when we first wake up. During the night, the digestive system slows down and the gut enters a sort of "pause." Upon awakening, it is more sensitive to any stimulus, and coffee—especially when drunk on an empty stomach—provides a strong and immediate signal, capable of rapidly reactivating intestinal activity.
At that time of day, the body is also governed by specific hormonal rhythms. As soon as we wake up, cortisol levels, the hormone that helps us wake up and stay alert, are at their highest. Cortisol also stimulates the digestive system, and therefore adds to the effect of coffee, enhancing it.
Another key factor is the gastrocolic reflex, a natural mechanism that connects the stomach to the intestine: when we ingest something, the stomach signals the colon that it can begin emptying. This reflex is most active in the morning, after an overnight fast, so coffee stimulates it at a time when the body is already ready to empty its bowels.
Finally, there's habit, and don't think it matters little. If you drink coffee first thing in the morning, your body gets used to this routine and learns to always react the same way, almost automatically: it's a "conditioned" effect that becomes predictable over time.
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