Is milk or coffee a laxative?: Comparing Their Effects on Your Digestive System

October 10, 2025 •

4 min read

According to one study, coffee stimulated the colon 60% more than water, while milk’s effect is often conditional on an individual's intolerance. So, is milk or coffee a laxative? The answer depends heavily on your body's specific response and overall digestive health.

Quick Summary

This nutritional guide compares the distinct digestive properties of milk and coffee. It details how coffee actively stimulates colon contractions for a more direct laxative effect, while milk's impact is tied to lactose intolerance. The information helps clarify which beverage is more likely to promote bowel movements versus potentially causing gastrointestinal discomfort.

Key Points

Coffee's Laxative Effect: Coffee actively promotes bowel movements by stimulating colon contractions and triggering hormonal responses, an effect amplified by caffeine and other compounds.
Milk's Conditional Impact: Milk is not a true laxative but can cause diarrhea or discomfort in individuals with lactose intolerance, affecting around 65% of the global population.
Decaf vs. Regular: Both caffeinated and decaffeinated coffee can stimulate the bowels, but the effect is more potent with regular coffee.
Fermented Dairy Benefits: Fermented milk products like yogurt and kefir contain probiotics that can aid digestion and are generally better tolerated than regular milk, especially for those with sensitivity.
Personalized Response: The effects of both coffee and milk vary significantly among individuals; paying attention to your body's specific reaction is crucial for managing digestive health.
Best for Regularity: For consistent laxative action, coffee is more reliable than milk, which can cause constipation in some people.

The Surprising Science Behind Coffee and Digestion

For many, a morning cup of coffee is the key to waking up their mind and, just as reliably, their bowels. This effect isn't a myth but a well-documented physiological response. Multiple factors contribute to coffee's ability to act as a laxative:

Caffeine: A known stimulant, caffeine does more than just perk up your brain; it also stimulates the smooth muscles of the colon, leading to increased contractions, known as peristalsis. These movements help propel waste through the intestines more quickly.
Hormonal Release: Drinking coffee triggers the release of several hormones that influence digestion, most notably gastrin and cholecystokinin (CCK). Gastrin stimulates the stomach to release acid and encourages colonic muscle contractions, while CCK can also increase bowel activity.
Other Compounds: The laxative effect is not solely due to caffeine. Studies show that even decaffeinated coffee can stimulate the colon, albeit to a lesser degree than its caffeinated counterpart. This suggests other compounds, like chlorogenic acids, are also at play.
The Gastrocolic Reflex: The act of drinking a warm beverage in the morning, when the colon is naturally more active, can amplify the gastrocolic reflex—a normal reflex that signals the colon to contract after eating or drinking. This timing and temperature can make coffee especially effective.

The Complicated Role of Milk in Digestive Health

Unlike coffee, milk's effect on digestion is not a consistent laxative action; in fact, for many, it can be quite the opposite. The primary reason milk can cause digestive issues is a condition known as lactose intolerance.

Lactose Intolerance: Approximately 65% of the world's population has a reduced ability to digest lactose, the natural sugar found in milk. When undigested lactose reaches the large intestine, bacteria ferment it, producing gas, bloating, and sometimes, diarrhea. This urgent bowel movement is a symptom of intolerance, not a true laxative effect, and is often accompanied by significant discomfort.
Methane Gas: In some individuals with lactose malabsorption, fermentation can produce methane gas, which has been shown to slow intestinal transit and potentially contribute to constipation. This directly contrasts the effect of a stimulant laxative.
High Fat Content: Adding significant amounts of cream or high-fat milk to coffee can also trigger the release of digestive juices from the pancreas and gallbladder, which can lead to increased water in the small intestine and diarrhea for some.
Constipation: For many without lactose intolerance, especially children, milk and dairy products can contribute to or worsen constipation. This is often due to its high density and lack of fiber.

Fermented Dairy: A Different Story

It is important to distinguish regular milk from fermented dairy products like yogurt and kefir. These products contain probiotics (beneficial bacteria) that can promote a healthy gut microbiome and aid in regular bowel movements.

Coffee vs. Milk: A Comparative Look at Laxative Potential


Feature	Coffee	Milk	Key Difference
Primary Mechanism	Stimulates colon contractions and hormone release (gastrin, CCK).	Triggers symptoms like diarrhea or constipation in individuals with lactose intolerance.	Coffee’s effect is a direct physiological response; milk’s effect is an intolerance symptom.
Consistency	The effect is common and often reliable for many people, both with and without caffeine.	The effect is inconsistent and depends on individual tolerance and gut microbiome.	Coffee is a more consistent choice for stimulating bowel movements.
Side Effects	Can cause jitters, anxiety, and stomach cramps, especially with high doses.	In intolerant individuals, causes bloating, gas, stomach pain, and general discomfort.	Coffee's side effects are related to stimulation, while milk's are related to maldigestion.
Effect on Constipation	Can be a helpful, natural remedy for constipation.	Can potentially worsen constipation due to methane production in intolerant individuals.	Coffee generally helps constipation, while milk can hinder it for some.
Nutritional Contribution	Contains antioxidants and has low calories (black).	Provides essential nutrients like calcium, protein, and vitamin D.	Coffee's benefit is digestive stimulation; milk’s is nutritional (with consideration for intolerance).

Making the Right Choice for Your Digestive Health

Choosing between milk and coffee for digestive health is not a one-size-fits-all decision. The best choice depends on your body's specific response and existing health conditions.

For Constipation: If you are constipated and do not have IBS or a caffeine sensitivity, a cup of coffee is a much more reliable choice for promoting a bowel movement. Starting the day with a warm, black coffee can leverage the natural morning activation of your digestive system. Water and fiber are still the foundation of healthy digestion, and alternatives like prune juice or herbal tea are excellent options.
For Digestive Discomfort: If you experience bloating, gas, or diarrhea after consuming milk, you may have lactose intolerance. In this case, avoiding regular dairy or switching to lactose-free alternatives, such as almond, oat, or soy milk, is recommended. Fermented dairy products like yogurt and kefir are also often well-tolerated and can support gut health.
Individual Sensitivity: Both beverages affect people differently. If coffee causes unwanted side effects like jitters or acid reflux, a switch to decaf or a lower-acidity brew might be helpful. Pay attention to how your body reacts to each drink and adjust your consumption accordingly. For some individuals with irritable bowel syndrome (IBS), coffee can trigger symptoms, while for others, its stimulating effect is not an issue. Listening to your body is always the best approach.

Conclusion

In the debate over whether is milk or coffee a laxative, coffee is the clear winner for its active stimulation of colon motility in many individuals. Its effect is rooted in its caffeine content and other compounds that trigger digestive reflexes. Milk, on the other hand, is not a laxative for the majority of the population and can cause discomfort or even constipation in those with lactose intolerance. Choosing the right beverage requires listening to your body's unique digestive signals and understanding the underlying science of how each one works.

For more information on digestion and nutrition, consult resources like the Cleveland Clinic's breakdown of coffee's effects on digestion.

Frequently Asked Questions

Yes, many people find that coffee can help relieve constipation. The caffeine and other compounds in coffee stimulate muscle contractions in the colon, which can trigger a bowel movement.

For individuals with lactose intolerance, milk can cause diarrhea, gas, and bloating. However, for those without this condition, milk and dairy products can sometimes be constipating due to their high density and lack of fiber.

Yes, decaf coffee can also have a laxative effect, though it is generally milder than caffeinated coffee. Compounds other than caffeine, such as chlorogenic acids, play a role in stimulating the digestive tract.

For those with lactose intolerance, the addition of milk or cream can cause symptoms like diarrhea because their bodies cannot properly digest the lactose sugar. The combination of coffee's stimulating effect and lactose intolerance symptoms can lead to a quick trip to the bathroom.

If both milk and coffee cause digestive issues, better alternatives include warm water with lemon, herbal tea, or prune juice. Increasing your intake of fiber and staying hydrated with plain water are also very effective strategies.

Yes, with regular consumption, your body can build a tolerance to coffee's stimulating effects. For some, this may result in a diminished laxative response over time.

For some sensitive individuals, the effects of coffee can be felt relatively quickly, sometimes within 30 minutes of consumption. However, the timing can vary significantly from person to person.