Why Does Coffee Make You Poop?

Photo credit: Anna Breit / Connect Archives

Written by Megan Falk: Experienced health and wellness journalist and editor. Megan is a graduate of Syracuse University’s S.I. Newhouse School of Public Communications, where she earned a bachelor’s degree in Magazine Journalism and a minor in Food Studies. She’s also a certified personal trainer through the American Council on Exercise.
Reviewed by Jennie O’Grady: Senior SciComms Specialist at Seed Health

Shortly after polishing off your morning cup of joe, you might experience a handful of side effects: a burst of energy that helps you power through the first few tasks on your to-do list, a feeling of full-body warmth that’s a relief in the ice-cold office, and a need to drop a deuce ASAP.

If the latter reaction sounds familiar, you’re in good company. While more recent data is lacking, in a 1990 survey of nearly 100 people, 29% of them reported feeling the urge to poop after drinking coffee.¹ 

So why does coffee make you poop? Due to a lack of recently published research, the answer isn’t totally clear, but there are a few potential mechanisms at play. Here’s what to know about coffee’s impact on your poop schedule—and gut microbiome as a whole—and how to use it to your advantage each morning. 

How Coffee Gets Things Moving

Broadly speaking, coffee can make you need to have a bowel movement for two reasons: It stimulates contractions of the colon, and it increases the production of hormones that kickstart the digestion process.

Below, the nitty-gritty breakdown of what’s going on in your body as you drink a latte or Americano.

1. It sets off the gastrocolic reflex.

Once you take your first sip of coffee, the beverage takes a journey from your mouth to your anus. Along the way, it travels through your digestive tract triggering the gastrocolic reflex—a normal physiological response that controls the movement of food through the intestines following a meal. 

On average, it takes about 28 hours for the food you eat to move from your mouth through your gut and come out your other end, but it’s considered “normal” for transit time to fall between 10 and 73 hours—and coffee can speed up the process.^2,3

Typically after eating food, the enteric nervous system (the part of the autonomic nervous system that manages gastrointestinal function), stretch receptors in the stomach, and certain hormones (more on those later) all work together to activate the gastrocolic reflex.^4,5 They send signals that tell your colon to contract, which helps to move the contents of your GI tract through your intestines toward your rectum. The goal: to make room for more food to be consumed.

Coffee may stimulate a similar reflex—even if you drink it without food. A small 1998 study found that caffeinated coffee stimulates colonic motor activity to a similar extent as a meal would.⁶ The exact mechanisms aren’t confirmed, but the beverage’s relatively high caffeine content may play a role. (For reference, a standard 8-ounce cup of joe will contain around 95 milligrams of caffeine—roughly equivalent to three cups of green tea or two cups of black tea.^7,8,9 Decaf coffee is also slightly caffeinated, and can contain ~2 milligrams in an 8-ounce pour.¹⁰)

A small 2008 study found that caffeine ingestion led to stronger contractions of the anal sphincter (the muscle that controls the release of stool) and an earlier desire to poop.¹¹ The stimulant has also been found to increase gastrointestinal motility and encourage contractions in the distal colon, effects observed both in caffeinated coffee and tea.¹² 

2. It releases hormones like gastrin and cholecystokinin.

Drinking coffee can trigger the release of gastrin—a hormone that promotes the secretion of gastric acid (an acid released by glands in the stomach wall that helps digest food).^13,14 It can also encourage the release of cholecystokinin, a hormone that regulates gut motility.¹⁴ They’re both known as mediators of the gastrocolic reflex.⁵ As a result of these hormones, food and liquid are encouraged to move through the intestines, which can lead to a bowel movement. 

Once again, the drink’s caffeine content may be a contributing factor. The stimulant on its own is known to activate gastric acid secretion, and studies have shown that caffeinated coffee stimulates the release of gastrin more effectively than decaf.^14,15

3. We usually drink it in the morning, when the colon is at its most active.

The post-coffee need to poop may be exacerbated in the morning, as colonic motor activity increases significantly when you wake up (hello, post-brekkie BMs).¹⁶ This is because your gastrointestinal system is regulated by your circadian clock genes.¹⁷ These genes tell it to settle down at night, quickly pick up its activity once you flutter your eyes open, and remain active throughout the day. 

Does the Type of Coffee Matter?

Though research has found a link between caffeine and coffee’s poop-inducing effect, there’s no clear consensus on whether caffeine content truly makes a difference in your need to visit the porcelain throne.

A small 1998 study found that muscles in the large intestine contracted more with caffeinated coffee than with decaf, but decaf coffee still had some effect on muscle contractions.⁶ In another study on rats that were given either decaffeinated or regular coffee for three days, the animals experienced similar increases in intestinal muscle contractions (which can lead to easier poops) with both types of joe.¹⁸

This tells us that some of the beverage’s other components are likely affecting digestion and bowel movements as well. For example, compounds like chlorogenic acids and N-alkanoyl-5-hydroxytryptamides (C5HTs) are found in coffee (regular and decaf varieties) and they may play a role in stimulating bowel movements by influencing gastric acid secretion.¹⁹ 

What Coffee Does to Your Gut More Broadly

In addition to prompting the urge to poo, caffeine and coffee may promote greater diversity in the gut microbiome.²⁰ That’s good news, as a diverse gut microbiome is generally considered “healthier” and better able to support bodily functions like digestion and immune responses. 

Plus, in a 2020 study, people who consumed 45 to 500 milliliters (a wide range that encompasses one-fifth of a cup to two cups) of coffee daily had higher levels of beneficial bacteria such as Prevotella.²¹ This genus of anaerobic bacterium ferments fiber to produce short-chain fatty acids (SCFAs)—byproducts that provide colon cells with energy, enhance gut barrier function, and carry anti-inflammatory properties.^22,23

A gut microbiome with a high species richness has also been linked with firmer stools; the less rich the microbial ecosystem, the looser the stool.²⁴ 

These changes in some bacterial populations may be due to coffee’s rich polyphenol content.^21,25 Polyphenols (organic compounds found in plant foods) can have anti-inflammatory and antioxidant effects (helping to protect cells from free-radical damage) and regulate the gut environment.²⁶ 

The coffee-derived polyphenol called chlorogenic acid may also act as a prebiotic—a substance that feeds certain “good” bacteria in the gut. Specifically, some types of chlorogenic acid feeds Bifidobacterium, a bacteria that helps break down food, absorb nutrients, and produce the SCFA acetate.^27,28 

That said, everybody reacts differently to coffee. And it’s important to weigh any potential benefits with sometimes unpleasant side effects. 

For some people, the drink may cause or aggravate heartburn by irritating the mucous membrane of the esophagus or triggering gastroesophageal reflux.²⁹ Research shows that caffeine may also increase feelings of anxiousness in some cases.³⁰

How to Tell If Your Coffee Poops Are “Normal”

The next time your morning cup sends you to the bathroom, we highly suggest peeking at your poop before you flush. Its shape and texture can give you helpful insight into your health—no expensive testing required. 

What should you be looking for? Human feces is roughly 75% water, with the remaining 25% being cellular lining, plant fibers, fats, proteins, mucus, bile, other substances your body couldn’t digest, and billions of teeny bacteria (and there’s nothing “gross” about any of it)! While every person is different, in general, a high-quality poop is soft and shaped like a sausage, either with a smooth or slightly lumpy texture.

Pass anything that looks different (think: separate, small chunks, mushy consistency), and you may be experiencing some GI distress. To quickly figure out how your stool rates, refer to the Bristol Stool Chart. 

What If Coffee Doesn’t Make Me Poop? Is That OK?

Reminder: Every person’s body (and microbiome) is different. So you might not feel the need to hit the bathroom after a cup of coffee—and that’s nothing to stress over. After all, that 1990 survey showed that the majority of people say they don’t experience this phenomenon. 

What’s more concerning is if you’re consistently struggling to poop and relying on coffee to get the job done. If you often have a difficult time passing stool, have infrequent bowel movements, or feel “blocked”—whether drinking coffee provides temporary comfort or not—you’ll want to raise it with your doctor. (FYI, some medications and medical conditions can contribute to these symptoms, too.) When your bowel habits change and you have blood in your poop, serious stomach pains, or lower back pain, that’s a clear signal to talk with your healthcare provider ASAP. 

Digestion Tips for Caffeine Lovers

To support a regular poop schedule and increase the odds of passing BMs worthy of a gold star, pair your morning coffee with these practices:

• Prioritize fiber intake: A lack of fiber can make you feel backed up, and studies have shown that a high-fiber diet can increase stool weight, helping to speed up how long it takes for it to move through your colon.³¹ You’ll want to make sure you’re getting a mix of both soluble and insoluble fiber: Soluble fibers dissolve in water and form viscous gels, while insoluble fibers do not dissolve in water and form the bulk of stool. Most plant foods contain both types, but if you’re short on the insoluble type, you may experience smaller, less frequent poops (no matter how much coffee you drink).
• Stay hydrated: Aim to drink a glass of water with your morning brew. Prioritizing fluid intake can make your stools softer and easier to pass, while dehydration may leave you feeling clogged up.³² 
• Take a daily probiotic: If you’re struggling to achieve consistent, healthy bowel movements through diet and lifestyle alone, consider adding a science-backed probiotic to your routine. In a 2010 study of 300 people who had trouble pooping or experienced digestive discomfort, participants who took two specific probiotic strains (Lactobacillus plantarum SD-LP1-IT and Bifidobacterium breve SD-BR3-IT) reported having more BMs each week, an easier time pooping, and less uncomfortable bloating.³³ Seed’s DS-01^® Daily Synbiotic is a 2-in-1 probiotic and prebiotic formulated with 24 probiotic strains including those leveraged in this research. And we’ve done the testing to ensure that this product lives up to its regularity claims: In a recent double-blind randomized placebo-controlled trial (the pinnacle of scientific research), DS-01^® was found to improve bowel movement frequency in individuals with occasional digestive issues.*³⁴ Take the probiotic first thing in the morning (or as part of your coffee ritual) to get the day off to a smooth—no pun intended—start.
• Manage stress: It’s no secret your mental health has an impact on your physical health, but its effect on your BMs might come as a surprise. When you’re feeling overwhelmed, you may be more likely to be backed up, as psychological stress influences gastrointestinal motility via the gut-brain axis.^35,36 To promote a relaxed mental state, consider practicing slow, deep breathing or a mindfulness meditation.³⁷ Be sure to cut off your coffee consumption early if you’re sensitive to caffeine so you don’t disrupt your sleep.

The Key Insight

It’s not unusual to need to hit the restroom after drinking a cup of coffee, thanks to the drink’s ability to trigger the gastrocolic reflex and the release of digestion-aiding hormones. The good news: There are other potential gut-health benefits to gain from your cup of joe, including a more diverse microbiome. 

Still, coffee may not be every person’s cup of tea, as some folks may experience side effects from the beverage, such as anxiety and heartburn. If that’s the case for you, don’t force yourself to chug a mug in the name of gut health and regular poops—you’ve got other options.