846. The internet has lots to say about how coffee affects your stomach. Unfortunately, most of it is wrong.
846. The internet has lots to say about how coffee affects your stomach. Unfortunately, most of it is wrong.
References:
Effects of Coffee and Its Components on the Gastrointestinal Tract and the Brain–Gut Axis - PMC
Effects of Coffee on the Gastro-Intestinal Tract: A Narrative Review and Literature Update
Pharmacology of caffeine and its effects on the human body - ScienceDirect
Related episodes
786 - How to beat acid reflux for good
841 - How long does caffeine really stay in your system?
Find a transcript here.
The internet loves to stir up fear around hidden dangers in our everyday habits—it’s guaranteed clickbait. Often, there are even a few kernels of truth–but they’ve been swaddled in layer after layer of false logic, incorrect assumptions, and misinterpretation. Today, I have a sterling example of all of the above, in the name of coffee. Let’s sort fact from fiction, shall we?
Welcome to the Nutrition Diva podcast, a show where we take a closer look at nutrition news, research, and trends so that you can feel more confident about what you eat. I’m your host, Monica Reinagel, and today’s episode was prompted by an article I recently came across in a major media outlet. It was one of those “listicle” pieces that the internet finds so irresistible: “Six Drinks You Should Never Have Drink on an Empty Stomach,” and the first one on the list was coffee.
A bunch of experts were quoted for the piece, but many of the statements were either misquoted, misleading, or just plain inaccurate. Naturally, I leapt right into myth-busting mode. But before I continue, I need to come clean with you: The first thing I do every morning when I wake up is make a cup of coffee, which I drink black, on an empty stomach. Sometimes, I have two. And then I often go to the gym and don’t eat breakfast until midmorning. So, obviously, I have a dog in this fight.
However, I’m also committed to providing you with the most accurate information I can. So, recognizing that I might be subject to a little confirmation bias, I took a little extra time to fact check myself on this one. (You’ll find some of the scientific references I consulted in the show notes.) I’m happy to say that those of us that like to start the day with a cup of coffee can probably continue to do so without any concern. And if someone you love is trying to tell you that your morning joe is shredding your stomach, allow me to offer some fact-based counterarguments.
Let’s start with the claim that coffee is hard on your stomach because it is so acidic. One of the experts quoted in the piece started by pointing out that “since coffee contains chlorogenic acids, it’s highly acidic,” which irritates the stomach lining.
This sounds perfectly reasonable, doesn’t it. Chlorogenic acid has the word “acid” right there in the name, after all. However, just because a food contains an organic acid, it doesn’t mean that it is very acidic.
In reality, brewed black coffee is only mildly acidic. On average, it has a pH of about 5. To put that in perspective, that is about the same pH as a squash. Even the most acidic coffees only drop down to a pH of around 4.7—which is roughly the same acidity as a banana. We are hardly talking about battery acid here.
Although coffee itself is not super acidic, it is true that the chlorogenic acids and caffeine it contains stimulate the cells in your stomach to secrete gastric acid (aka stomach acid). Stomach acid is a whole lot more acidic than coffee, but this is still not necessarily a problem for most people. The stomach is a very acidic environment by design–that acid plays a critical role in digestion. And the stomach is lined with special cells that protect it from that acidic environment.
Now, coffee can be a trigger for some people who suffer from acid reflux or GERD. As I’ve talked about in previous episodes, the dietary triggers for reflux are not universal. They really vary from person to person. But if coffee is a reflux trigger for you, it’s likely to happen whether or not you have food in your stomach. In fact, having too much food in your stomach may actually make reflux more likely because it exerts upward pressure on the lower esophageal sphincter–that’s the muscle at the top of the stomach that is supposed to prevent acid from reversing (or refluxing) into the esophagus.
But the point I really want to make here is that drinking coffee on an empty stomach generally does not cause stomach irritation. If it’s not causing you any discomfort, you probably do not need to worry about it.
Another misleading statement that I wanted to address is that coffee "can increase gastric motility, which can irritate the stomach lining." Let's break that down into two parts, because one part is true and the other is…not.
It is absolutely true that coffee increases gastrointestinal motility, or the speed at which things move through your digestive system. This is often a welcome effect, if you know what I mean. Studies show that caffeinated coffee can significantly increase colonic motor activity. In plain English: Coffee makes you poop.
But this does not irritate the lining of your stomach. That increased motility is happening mainly in the colon, not the stomach. There is no evidence connecting increased gut motility to gastritis or an irritated stomach lining. So, yes, coffee speeds things up, but no, that is not a sign of irritation or injury to the lining of your stomach (or your colon, for that matter).
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The article also claimed that “having coffee on an empty stomach can lead to… anxiety, jitters, shakiness, and a faster heart rate.” Again, I think they are linking together some unrelated things.
Caffeine is a central nervous system stimulant. It makes us feel more alert. However, if you are very sensitive to caffeine (or you just have way too much of it), that CNS stimulation can cause a pounding heart, jitters, shakiness, or anxiety. But this is only minimally impacted by whether or not your stomach is empty.
Having some food in your stomach may delay or blunt the delivery of caffeine into your bloodstream. But how much caffeine you take in and your individual sensitivity are much bigger players. In other words, if you are highly sensitive to caffeine, you will likely experience those jitters whether you drink it with food or without. You’re probably better off avoiding caffeine altogether.
Finally, let's talk about one expert’s suggestion that adding milk to your coffee will "lower the acidity," making it gentler on your stomach. Milk does not lower the acidity of coffee as much as you might think. The pH of milk is only slightly higher (i.e., less acidic) than that of black coffee. More importantly, as we have already talked about, the acidity of the beverage isn’t really the problem.
That said, adding milk to your coffee may still help, but for a completely different reason than the one suggested here. The proteins in milk can bind to the chlorogenic acids and other polyphenols in the coffee. This makes these compounds less absorbable, which may reduce their ability to stimulate gastric acid secretion.
Now, you may have caught that I said that milk proteins bind to “other polyphenols” as well. And aren’t polyphenols generally a good thing? Good catch! Yes, polyphenols are a broad class of plant-based antioxidants, which are responsible for many of the benefits we get from eating fruits and vegetables. And from drinking coffee! (This is a good place to mention that coffee is actually the #1 source of antioxidants in the typical American diet!)
So, does that mean that adding milk to your coffee might not only reduce gastric acid secretion but also reduce its antioxidant potential? Well, yes but also no. Milk can reduce the absorption of some of those polyphenols. On the other hand, the milk itself adds some antioxidants and may protect some of the polyphenols in coffee from breaking down. The bottom line is that even with milk (or plant milk), coffee remains an antioxidant rich drink.
Whether or not you like milk in your coffee, you can reduce the chlorogenic acid content by choosing a darker roast. Yes, you heard me correctly. Roasting reduces the chlorogenic acid content of coffee beans, and also creates a compound called NMP, which actively suppresses gastric acid secretion. The longer the coffee is roasted, the less chlorogenic acid and the more NMP it contains. So, if your stomach is sensitive, a dark roast is potentially more stomach-friendly, even though it tastes "stronger."
Choosing cold brew can also help. Brewing with cold water extracts less of the chlorogenic acid and caffeine from the beans. Less extraction means you’re taking in less of the compounds that stimulate gastric acid secretion.
But to get back to the main question here: The evidence really does not support the claim that you should “never” drink coffee on an empty stomach. If it’s not causing any discomfort, there’s no reason to think it’s harming you.
If you have a question you'd like me to answer or a claim you’d like me to fact-check, you can email me at nutrition@quickanddirtytips.com. If you'd like to find out about having me speak at your next live or virtual event, you'll find more information at wellnessworkshere.com.
Nutrition Diva is a Quick and Dirty Tips podcast. Holly Hutchings is our Director of Podcasts. Steve Riekeberg is our audio engineer, Morgan Christianson heads up Podcast Operations & Advertising, Rebekah Sebastian is our Manager of Marketing and Publicity and Nat Hoopes is our Marketing and Operations Assistant. Thanks to all of them and thanks to you for listening!