What are the side effects of coffee with milk?

December 30, 2025 •

3 min read

According to a study from the University of Copenhagen, the combination of milk proteins and coffee polyphenols can double the anti-inflammatory properties of immune cells. However, for many, this popular pairing can also lead to an array of unpleasant side effects, particularly relating to digestive health and nutrient absorption.

Quick Summary

The side effects of coffee with milk often stem from lactose intolerance, caffeine sensitivity, and increased stomach acid production, leading to issues like bloating, acid reflux, and diarrhea. Nutrient absorption can also be hindered, affecting iron uptake. Timing and consumption habits play a crucial role in managing these potential health concerns.

Key Points

Digestive Upset: The combination of milk (lactose intolerance) and coffee (acidic) can lead to bloating, gas, and stomach cramps.
Increased Acidity: Caffeine in coffee stimulates stomach acid production, which, especially on an empty stomach, can trigger or worsen heartburn and acid reflux.
Impact on Iron Absorption: Both milk and coffee can hinder iron absorption, making this combination a concern for those with low iron levels.
Bioavailability of Antioxidants: Some studies suggest that milk proteins may reduce the bioavailability of coffee's beneficial polyphenols, though research is inconclusive.
Calorie and Sugar Content: Adding milk and sugar significantly increases the calorie count of coffee, which can be a drawback for weight management goals.
Best Practices: To mitigate side effects, consume milk coffee after meals, consider plant-based milks, or try lower-acid coffee options.

Unpacking the Digestive Discomforts

One of the most common complaints associated with coffee and milk is digestive distress. This can be attributed to several factors, with lactose intolerance and caffeine sensitivity being the primary culprits. For those lacking the lactase enzyme, consuming milk leads to undigested lactose, which can cause significant discomfort, including bloating, gas, stomach cramps, and diarrhea. Moreover, drinking milk coffee on an empty stomach can increase the production of hydrochloric acid, irritating the stomach lining and potentially leading to nausea and indigestion.

The Role of Caffeine and Acidity

Coffee, even without milk, is known to stimulate the production of stomach acid due to its caffeine and other compounds like chlorogenic acid. For individuals with a sensitive stomach or conditions like gastroesophageal reflux disease (GERD), this can trigger heartburn and acid reflux. When combined with milk, which can slow down digestion, this effect may be exacerbated for some, though research results are mixed.

A Deeper Look at Nutrient Absorption

Another lesser-known side effect of mixing coffee with milk is the potential impact on nutrient absorption. Research indicates that the tannins and polyphenols found in coffee can interfere with the body's ability to absorb iron. The added calcium from milk can further complicate this by inhibiting iron absorption. This is particularly concerning for individuals with low iron levels or anemia, who should be mindful of consuming this beverage, especially around mealtimes.

Potential Interference with Antioxidants

While the anti-inflammatory benefits of coffee with milk have been highlighted, some studies suggest a reduction in the bioavailability of coffee's antioxidants (polyphenols) when combined with milk proteins. While more recent research provides conflicting evidence, indicating that the overall health benefits might not be significantly compromised, it remains a point of consideration for those who drink coffee primarily for its antioxidant properties.

Comparison: Coffee with Milk vs. Black Coffee

To better understand the distinct side effects, a comparison between drinking coffee with milk and drinking it black is useful.


Aspect	Coffee with Milk	Black Coffee
Digestive Issues	Higher risk for those with lactose intolerance; potential for bloating, gas, and diarrhea. Increased risk of acid reflux when consumed on an empty stomach.	Can still cause stomach irritation and increase acid production, especially in sensitive individuals. No risk of lactose-related issues.
Nutrient Absorption	Potential for reduced iron absorption due to combination of coffee polyphenols and milk calcium.	Tannins and polyphenols can inhibit iron absorption, but the effect is not compounded by milk.
Antioxidant Effect	Some studies suggest milk proteins may reduce polyphenol bioavailability, though evidence is mixed.	All antioxidants from coffee are fully available, offering potent anti-inflammatory and other benefits.
Calorie Count	Higher in calories and potentially sugar, especially if using whole milk or flavored additions.	Contains virtually no calories, making it a better option for weight management.
Impact on Fasting	Breaks a fast due to the calories in milk.	Does not break a fast, making it compatible with intermittent fasting.

Practical Tips for Managing Side Effects

To enjoy your coffee with milk without the negative side effects, consider these tips:

Consider your tolerance: If you experience gas, bloating, or diarrhea, try switching to a lactose-free or plant-based milk alternative like soy or almond milk.
Don't drink on an empty stomach: Consuming coffee with food can help mitigate the impact of increased stomach acid and reduce irritation.
Reduce your intake: For those sensitive to caffeine, cutting back on the total amount of coffee or switching to decaf can help, as decaf has fewer gastric effects.
Monitor your iron levels: If you are at risk for anemia, consume your coffee with milk separately from iron-rich meals to minimize interference with absorption.
Lower the acidity: Experimenting with a low-acid coffee roast or a cold brew, which is naturally less acidic, may help those who suffer from acid reflux.

Conclusion: Personal Preference and Mindful Consumption

Ultimately, whether coffee with milk is problematic depends heavily on individual sensitivities and habits. While it offers unique benefits, such as a potential anti-inflammatory boost and a less acidic experience for some, it also presents potential downsides related to digestion and nutrient absorption. The most effective approach is to listen to your body, experiment with different types of coffee and milk, and practice mindful consumption to minimize any adverse reactions. By understanding the causes behind the side effects, you can make informed choices and continue to enjoy your daily cup, your way.

Frequently Asked Questions

Yes, coffee with milk can cause stomach pain due to several factors, including lactose intolerance, increased stomach acid production from caffeine, and delayed digestion.

For most people, drinking coffee with milk daily in moderation is not harmful. However, it can be problematic for individuals who are lactose intolerant, have caffeine sensitivity, or suffer from acid reflux.

While milk can temporarily act as a buffer against stomach acid, it can also stimulate the stomach to produce more acid later on, potentially worsening acid reflux symptoms. Low-acid coffee blends are a better solution.

Some studies suggest that milk proteins might reduce the absorption of certain coffee antioxidants, but other research has shown that benefits are largely maintained or even enhanced in some cases. The overall effect remains a subject of debate.

For those with digestive issues, good alternatives to cow's milk include lactose-free milk, or plant-based options such as soy, almond, or oat milk, which are generally easier to digest.

Yes, it is often advised to avoid drinking milk coffee on an empty stomach. The combination can increase stomach acid and irritate the stomach lining, leading to indigestion and heartburn.

Yes, the tannins and polyphenols in coffee can inhibit iron absorption, and the calcium in milk can further intensify this effect. This is particularly relevant for those prone to anemia.