Tips to Brew Coffee That Won't Irritate Your Stomach

Some studies have linked coffee consumption to certain health benefits. However, coffee doesn’t always love people’s digestive systems.

Two iced coffees in glass mugs on an outside table
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In fact, some studies say it could lead to symptoms such as heartburn or dyspepsia, acid indigestion, and reflux. Generally, that's because coffee causes an increase in stomach acid. This leaves people who enjoy coffee looking for solutions to this problem.

Here’s where researchers step in to look for answers. Scientists have broken down which compounds are found in coffee and whether they can be adjusted in order to make a more palatable brew. Could drinking certain varieties of coffee cut down on some of the stomach issues experienced by coffee lovers?

Lower Acid Coffee

For this article, lower acid coffee is in reference to pH levels—lower pH levels are more acidic and higher ones are more basic. Roasting coffee beans produces coffee that’s lower in acidity and cold brewing also imparts this effect because fewer compounds are imparted into the coffee when it is cold brewed.

Certain varieties of coffee are also naturally less acidic, which may be a result of being grown at a lower elevation or using particular drying methods. Lower acid coffee is available in a variety of flavors and roast options.

Some people might enjoy the taste of coffee with a lower acid content, as it tends to be smoother and milder than coffee with a higher acidity. Others would miss what connoisseurs describe as the “brightness” of a brew with its natural pH level intact.

However, it’s not likely that it is the actual acid content in coffee that causes the stomach upset. Coffee has a lower acid content on average than, for instance, tomato juice and orange juice.

There’s probably no harm in trying it to see if lower acid coffee decreases symptoms. However, there isn’t any good evidence that it is the actual acid that most people find problematic about drinking coffee.

Beneficial Compound N-methylpyridinium

The chemical compound N-methylpyridinium (NMP) may offer some clues into how to make a coffee that doesn’t bring on stomach discomfort. Some studies published in 2014 found that coffee that contains higher concentrations of NMP causes less stomach acid to be secreted, meaning that there are fewer gastric juices to bring on symptoms of heartburn.

This begs the question: why don’t we use NMP as a treatment to lower stomach acid? Turns out, it’s not quite that simple. Putting NMP right on top of stomach cells didn’t have the same effect, so it’s clear that there’s more to the story and that the compounds in coffee are working together in a complex way to influence the release of gastric acids.

Chlorogenic Acids May Be the Culprit

Other compounds in coffee studied for their effects on stomach acid include (β) N-alkanoyl-5-hydroxytryptamides (C5HTs) and chlorogenic acids (CGAs).

The 2014 study showed that when the NMP content in coffee was higher and the C5HT and CGA content was lower, there was less stomach acid produced by the study participants.

So, while NMP is a key compound in the search for a coffee that doesn’t cause symptoms, the presence of C5HT and CGA in lower concentrations also has an effect. The best combination for finding a stomach-friendly coffee brew then is going to be one that is lower in chlorogenic acids and higher in NMP.

Adding milk to coffee may also help it to become more stomach-friendly, at least for those who are able to have milk.

When milk is added to coffee, several milk proteins, including α-casein, β-casein, κ-casein, α-lactalbumin, and β-lactoglobulin, will bind to the chlorogenic acids.

With the chlorogenic acid being bound by a protein, it is not going to do its work to increase stomach acid because it is less bioavailable (which is a measure of how easily a compound is absorbed up by the body).

Dark Roasting for Balance

Contrary to what might seem to be true, it is the dark roast varieties that may be the coffee that's easiest on the stomach. The 2014 study showed that a dark roast, compared to a medium roast, has increased NMP content and decreased chlorogenic acid content.

For those looking for a coffee easier on the stomach, a dark roast, which may have fewer of the compounds that increase stomach acid and more of the chemicals that decrease stomach acid, is going to offer the greatest chance of a coffee that doesn’t cause symptoms.

Double-Fermented Coffee

Makers of double-fermented coffees claim that the process by which their coffee beans are treated can result in coffee that’s easier on the stomach. When most people think of fermented foods they think of probiotics, but coffee processed this way is not going to naturally contain any bacteria that’s beneficial to the digestive system.

Coffee is typically fermented once, but some manufacturers add a second fermentation, also sometimes called a “double soak” or a "double Kenya fermentation” because coffee from Kenya is known for this process.

The idea is that the double fermentation can remove the “bitter notes” and make the coffee more palatable to people who have digestive issues. It is the chlorogenic acids in coffee that are at least partly responsible for the bitter taste. Therefore, the idea is, the less bitter the coffee, the fewer chlorogenic acids are present.

However, there’s no evidence yet that double fermenting does, in fact, reduce the amount of chlorogenic acids, or increase the NMP content, both of which are needed to create coffee that reduces stomach acid production.

Green Coffee (Unroasted)

Green coffee is a variety of coffee bean that has not undergone a roasting process. Without roasting the beans, the chlorogenic acids and the NMP content of the brewed coffee are not going to be altered, and the result is a coffee that’s not going to have any benefits on reducing stomach acid production.

In addition, coffee brewed from unroasted beans may have a bitter taste, due to the higher chlorogenic acid content.

Does Caffeine Content Matter?

What many coffee drinkers enjoy about coffee is not a secret: it’s the caffeine content. It puts the get-up-and-go in the morning, and for some, in the afternoon too. However, most studies show that caffeine doesn’t seem to be an issue when considering coffee’s effects on the stomach.

Some studies that looked at various coffee blends and their effect on stomach acid production used coffees that were similar in caffeine content in order to even the playing field. It’s thought that the bioactive compounds found in coffee that increase or decrease digestive juices in the stomach may interact with each other no matter how much caffeine is in the coffee.

However, a study published in 2017 suggests that caffeine does have an effect on stomach acid production because it also has a bitter flavor.

Individual Effects

Another piece of the puzzle is how the individual person reacts to the compounds and the caffeine content in coffee. While broad recommendations can be made from scientific studies, there are genetic variations that may influence how any one person reacts to the compounds in coffee.

There’s a limit to this variation, so it might not be terribly important for most people, But this does mean that there could be some trial and error involved.

The coffee that one person swears by and is able to drink without having heartburn may not work the same way for everyone. This means that trying different brands may be a part of finding a coffee that is easier to digest.

Brewing Coffee That Won't Cause Stomach Irritation

Based on the research available, in short, here's what may help:

  • Go for dark roast. It might seem that the darker the coffee, the more stomach symptoms it might bring on, but the opposite is actually true. Roasting coffee brings out the best in a natural compound that actually suppresses the production of stomach acid.
  • Use a cold brewing method. Cold brew is going to result in a coffee that has lower levels of all the compounds found in coffee. This means that the parts of coffee that cause an increase in stomach acid are going to be lower.
  • Add milk. If you don't have issues with dairy (such as a dairy allergy or lactose intolerance), milk proteins combine with some of the compounds in coffee that tend to increase stomach acid.

A Word From Verywell

While there’s been some study on how and why certain types of coffee may cause less production of stomach acids than other varieties, there’s still so much more to learn about this complex process.

Finding a coffee high in NMP and low in chlorogenic acids might result in fewer stomach symptoms after drinking it. This effect might be increased through the use of a cold brewing method and adding milk.

However, a certain amount of trial and error might be needed because coffee makers don’t typically advertise the NMP and chlorogenic acid content of their beans! With the vast array of coffees on the market, however, there’s likely to be one that comes with fewer stomach upset.

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