For the millions of caffeine junkies out there, your morning cup of coffee is a blissful escape from a grumpy, foggy hell. It's also packed with antioxidants that protect your brain and body.
But one downside of needing an IV drip of java upon waking is the morning coffee rumble. It can hit as soon as you take your first sip or wait to strike just as you sit down for a 9AM meeting. One study found that 29% of people have to poop within 20 minutes of drinking a cup of coffee.
But is this effect really taking place in your gut, or is it just your imagination?
We dug into the latest cutting-edge research to answer this important question once and for all. It turns out things are more complicated than we thought.
Why Does Coffee Make You Poop?
The phenomenon of coffee causing bowel movements has been widely documented (often in graphic detail). However, the scientific community has yet to reach a verdict on why it actually happens.
There are obviously more important matters to study than why you always take a dump after chugging your iced coffee. Nevertheless, there are a handful of studies that can point us in the right direction.
Let's unpack four theories that explain why coffee makes you poop.
1. Caffeine Triggers Colon Contractions
Caffeine stimulates your brain, but it also stimulates an important type of contraction in your colon called "peristalsis." These contractions push your stool closer and closer to the light at the end of the tunnel, speeding up the urge to poop.
In 1998, researchers tested this theory by putting sensor probes up twelve people's butts—bear with us. Throughout the next day, the participants consumed warm coffee, decaf coffee, water, or a meal in a random order. The results? Caffeinated coffee was 60% better at stimulating colonic activity than water, 23% better than decaf, and about the same as a meal.
This may also explain why an energy drink or pre-workout supplement with a high amount of caffeine gives you the runs too.
2. Coffee Stimulates Digestive Hormones
Coffee has over 1,000 aroma compounds that stimulate three hormones that trigger bowel movements.
First is the hormone gastrin, which kickstarts the production of gastric acid (AKA stomach acid) in your digestive tract.
The second hormone is called cholecystokinin, which is produced by your small intestine. This stimulates the production of bile and digestive enzymes.
Lastly, the Washington Post notes that a coffee compound called chlorogenic acid stimulates stomach and gastric acid production, which could force your colon to push quicker than expected.
3. Your Body Likes Pooping at the Same Time Every Day
Your brain and butt "talk" to each other through the gut-brain axis. This explains why you (probably) poop around the same time every day: your body likes having a routine.
If your morning ritual involves pooping and drinking coffee, your brain links the two acts together, regardless of all the factors we mentioned above. Think of it like muscle memory, but for your rectum.
It's also worth noting that your colon is twice as active in the morning compared to when you're asleep. This creates the perfect storm for the coffee rumbles.
4. The Stuff You Put In Your Coffee Counts Too
About 35% of people drink their coffee black. But if you're among the majority that brings milk or cream into the mix, your digestive system could be in double trouble.
Nearly 7 out of 10 people have some degree of lactose intolerance, meaning they can't fully digest dairy products. This often leads to bloating, cramping, and the "gastrocolic reflex," AKA the sudden urge to defecate.
Sugar and artificial sweeteners like sorbitol are notorious for having laxative effects too, according to Harvard Health.
Do the math: coffee plus dairy plus sugar equals a recipe for an explosive coffee poop.
Does Coffee Make Everyone Poop?
While post-coffee poops are common and totally normal, the majority of people don't seem to be affected by this phenomenon. A widely-cited study in Gut found that just 29% of people had the urge to poop within four minutes of drinking coffee—a sensation that lasted "at least 30 minutes."
63% of these coffee poopers were women (yes, girls poop). The theory here is that women are more prone to digestive conditions like irritable bowel syndrome (IBS) which can be exacerbated by the effects of coffee.
It's very possible that more than 29% get the coffee rumbles. The study we cited is small and quite old, so more research is necessary to get the full picture. That said, it might be hard to wrangle busy adults who are cool with scientists observing their pooping habits.
Does Decaf Coffee Make You Poop?
Decaffeinated coffee also revs up your gastrointestinal tract, but not as aggressively as full-caf coffee. This study found that people's "colonic motor activity" was 23% stronger after drinking regular coffee than decaf coffee.
So while the caffeine content is definitely linked to the urge to poop, it's not the only factor. Decaf coffee is still packed with aroma compounds that tell your body it's time to go.
Defend Your Drawers from Coffee Poops with DUDE Wipes
To review, coffee definitely makes you poop (and so do these other laxative drinks). Once it hits your digestive tract, your next move will likely be toward the toilet. However, scientists still don't know exactly what causes this poopy reaction.
If you'd like to avoid emergency coffee turds in the future, try to hold off on drinking any coffee for a couple hours after you wake up. By then, your body's natural desire to evacuate in the morning will pass, removing a major risk factor in coffee-caused poop-tastrophes.
For the fiends out there whose synapses don't begin to fire until coffee hits your bloodstream, you're putting your drawers and dignity on the line every morning. Be sure to pack a DUDE Wipe and thank us later.