Why Does Coffee Upset Your Stomach?

You probably won't be surprised to hear that I drink a lot of coffee. That said, I'm one of the fortunate ones -- no matter how much coffee I drink, I never seem to suffer any ill effects. Other than a few sleepless nights after tasting too much espresso, that is. Still, coffee can cause nausea and an upset stomach in many people.

Café caliente en taza corporativa de Coffeeness

You probably won’t be surprised to hear that I drink a lot of coffee. That said, I’m one of the fortunate ones — no matter how much coffee I drink, I never seem to suffer any ill effects. Other than a few sleepless nights after tasting too much espresso, that is. Still, coffee can cause nausea and an upset stomach in many people.

What’s worse is that coffee can start to upset your stomach after you’ve been drinking it for years without issues.

Don’t worry — I’m not about to recommend you give up your morning pour-over or afternoon espresso macchiato. In this article I’ll take a look at the reasons why coffee can cause an upset stomach and offer tips for preventing that sinking feeling. Help is on the way!

Acidity: Root Cause or Scapegoat?

Ask any non-coffee drinker what they don’t like about coffee, and their response will most likely involve the words “bitter” and “acidic.” It’s fairly easy to reassure someone that bitterness only occurs in coffee that hasn’t been properly extracted, but explaining away the concept of acidity in coffee is more difficult. 

There’s a long-held belief that coffee is an acidic beverage. This acidity supposedly causes heartburn, indigestion, acid reflux and a host of other stomach-related maladies.

However, when coffee professionals talk about acidity in coffee, they’re referring to pleasant, sought-after characteristics. 

High-quality coffee should feature bright, sparkling notes (acidity), balanced out by, sweetness, more chocolatey notes and body.

In other words, the pros are describing perceived acidity — the same thing you experience when biting into a good apple. 

Preparing coffee in a Chemex.

To understand how acidic coffee actually is, we need to get slightly scientific and look at where it sits on the pH scale.

Remember: the lower the number, the higher the acidity. Let’s compare a few examples:

  • Neutral pH: 7
  • Bottled water: Around 6
  • Milk: 6.5
  • Coffee: 4.85-5.13
  • Ripe banana: 5
  • Orange juice: 3.5

So, coffee really isn’t that acidic after all. It has the same pH as a banana, and who has ever thought of a banana as an acid bomb?

Sure, coffee contains acids like chlorogenic acid and N-alkanyol-5-hydroxtrymtamide (try saying that three times in a row), but it isn’t coffee’s acidic nature that causes digestive issues.

Rather, it’s the acid in your stomach that’s to blame. Drinking coffee increases stomach acid production, and for some people that leads to trouble.

Tips for Avoiding an Acid-Related Upset Stomach

If you’re among the unfortunate folks who get an upset stomach after drinking coffee, consider the following:

  • Some coffees are substantially lower in acid than others, depending on factors like elevation and processing. A natural process Ethiopian coffee will be way less acidic than a fully washed Kenyan coffee, for example.
  • Coffee that’s been brewed hot will be much more acidic than cold brew coffee.
  • Dark roast coffee contains a balance of chemical compounds that produce less stomach acid than lighter roasts.

Caffeine: A More Likely Culprit

I’ve never understood those people who claim to only drink coffee for the caffeine. After all, there’s so much more to enjoy and appreciate than just a quick fix. There’s a reason we talk about “coffee culture” and not “energy drink culture.” 

An image of a caffeine molecule made from coffee beans.

Still, the caffeine buzz we get each morning (and afternoon) is a big part of the attraction. Caffeine is a drug, plain and simple. It’s a mental stimulant that offers clarity, focus and energy, and it keeps us coming back for more. 

You’ll know from experience that caffeine stimulates your digestive system, too. In fact, just the smell of coffee brewing in the morning can get things moving, so to speak.

Once caffeine hits your system, it acts as a natural laxative, forcing your digestive system to work harder and faster than it might want to. There’s no doubt this can lead to an upset stomach at the very least.

Moreover, just like the aforementioned natural acids in coffee, our favorite legal drug stimulates the production of stomach acid, which can lead to significant discomfort.

Preventing a Caffeine-Related Upset Stomach

I’m not about to recommend decaf coffee, but there are ways to combat the caffeine blues:

  1. Drink less coffee. Close your eyes, take a deep breath and ask yourself whether you’re drinking too many cups a day. Everyone has different needs, but if you’re at three cups by noon and you have an upset stomach every day, it may be time to cut back.
  2. Avoid Robusta. In my article on Arabica vs Robusta, I talk about how Robusta’s caffeine content is notorious for causing an upset stomach. Robusta is produced at lower altitudes than Arabica, and has to deal with more pests. That’s why this type of coffee contains so much caffeine — it acts as a natural defense mechanism. Although roasters don’t always advertise it, they’ll sometimes add Robusta to a blend. Do your research, and try to buy coffee that’s 100% Arabica.
  3. Eat a banana. If your stomach is rumbling and churning after a few sips, eating a banana might calm things down. Aside from providing some alkalinity to combat stomach acid, a banana contains a variety of indigestion-soothing substances.

Milk: Not Always Innocent

There’s no doubt that milk and coffee go great together. If the milk is steamed and those sugars are nicely caramelized, adding a shot of espresso or two will result in a marriage made in heaven. 

In some cases, adding milk foam or cream to coffee will benefit your digestion. Some of the milk’s proteins bind to the coffee’s chlorogenic acid, preventing it from stimulating acid production in your stomach. 

A closeup of a latte macchiato from a super automatic espresso machine.

However, lots of people are — to a greater or lesser degree — sensitive to dairy products. It’s often the case that a lactose-intolerant person has no idea what milk and cheese are doing to their system. They’ll blame their upset stomach and bloating on just about anything else — including coffee. 

So, before you point the finger at the espresso in your daily 16-ounce latte macchiato, think about all that milk. Try experimenting with a plant-based alternative — oat milk, in particular, foams up really nicely. I’ve had great results using Oatly oat milk.

While you’re at it, ditch the syrup, sugar and whipped cream. They’re bad for your teeth, bad for your figure and do nothing to enhance the flavor of coffee.

The Remedy for an Upset Stomach From Coffee: Is Cold Brew the Answer?

Whichever preparation method you’re using, an under or over-extracted cup of coffee will wreak havoc on your insides.

Incorrectly prepared pour-over coffee or a French press that’s been sitting for too long will result in a cup that’s completely out of balance. It won’t do your stomach any favors, either.

Still, even perfectly extracted coffee varies in caffeine content and acidity, depending on how it’s been brewed. 

Cold brew coffee in a mason jar for upset stomach.

Many people swear by cold brew coffee, claiming it’s the only way they can drink coffee without suffering from an upset stomach. The facts certainly back that up.

Cold water doesn’t extract compounds from ground coffee in the same way as hot water, so you end up with dramatically lower acidity and sometimes even less caffeine content than espresso.

In my guide to cold brew coffee, I offer tips and ideas for how to get the best out of this simple preparation method.

I’ll also add that there’s no reason you can’t make cold brew concentrate at home then dilute it with hot water for a delicious and smooth cup of coffee.

Conclusion: Don't Skip Breakfast

You’re halfway through your morning cup of coffee when the feeling strikes: sweaty palms, shaky hands and a rumbling, uncomfortable stomach. It’s only then that you realize you’ve forgotten to eat breakfast. As we’ve already seen, coffee is a powerful force that stimulates stomach acid production and acts as a laxative. If your stomach is empty when the coffee shows up, you’re just asking for trouble.

When you’re particularly sensitive to coffee’s stimulating effects, you should choose your breakfast wisely. Forget the greasy bacon and eggs — they’ll just make matters worse.

You can avoid an upset stomach from coffee by eating milder food like bread, oatmeal and granola, all of which will line your stomach and help slow down your body’s reaction to caffeine.

Don’t forget that eating a banana will help calm you down if you’re feeling too buzzed. And remember to drink plenty of water!

What’s your experience? Do you have a magic cure for an upset stomach from coffee? I look forward to your comments!

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