Part of our Mushroom Coffee guide library.
Short answer: Yes, coffee is mildly acidic. In one study, both hot and cold brew coffee had a pH of about 4.85 to 5.13, where 7 is neutral. Cold brew had the same pH as hot coffee, though hot brew had more total acid. For your stomach, the acidity of the drink matters less than what coffee does inside you: caffeine increases stomach acid, which can cause an upset stomach or heartburn. Coffee is one of the drinks commonly linked to reflux symptoms, so if it bothers you, a smaller cup, less caffeine or drinking it with food may help.
If coffee gives you heartburn or an upset stomach, it is natural to blame its acidity. But how acidic is coffee really, and is that the problem? Here is what the pH numbers mean, how cold brew, dark roast and decaf compare, and what research says about coffee and acid reflux.
What you'll learn
- How acidic coffee is, and what pH means
- Whether cold brew, dark roast or decaf is less acidic
- How coffee affects stomach acid and reflux
- What to try if coffee upsets your stomach
What pH means
pH measures how acidic or basic a liquid is on a scale from 0 to 14. A pH of 7 is neutral, anything below 7 is acidic and anything above 7 is basic. The scale is logarithmic, so each step is a 10-fold change: a pH of 5 is ten times more acidic than a pH of 6 (USGS).
How acidic is coffee?
Coffee is mildly acidic. A study of light roast coffees from six growing regions found that both cold brew and hot brew had a pH between about 4.85 and 5.13 (Rao & Fuller, 2018). That puts coffee clearly on the acidic side of neutral, but closer to neutral than strongly acidic liquids. Coffee contains several natural acids, and how many end up in your cup depends on the beans, roast and brewing method.
Is cold brew less acidic?
Not by pH. In the same study, cold brew and hot brew made with the same ratio of coffee to water had comparable pH values. The difference was in total titratable acid, a measure of the total amount of acid: hot brew had more of it than cold brew (Rao & Fuller, 2018). So cold brew may taste smoother to some people, but it is not meaningfully less acidic on the pH scale. For an easy home version, see how to make iced coffee.
Is dark roast less acidic?
There is limited evidence. In a small study of nine healthy volunteers, a dark roast blend stimulated less stomach acid than a medium roast blend with a similar amount of caffeine. The dark roast had more of a compound formed during roasting (N-methylpyridinium) and fewer chlorogenic acids (Rubach et al., 2014). The authors said further studies are needed, so treat this as a possible option to try rather than a proven fix.
Is decaf coffee acidic?
Decaf is made from coffee beans too, so it is still an acidic drink. We could not find reliable pH measurements comparing decaf with regular coffee. In a large study of reflux symptoms, results were similar for caffeinated and decaffeinated drinks (Mehta et al., 2020), so switching to decaf may not solve reflux for everyone, though it does remove most of the caffeine. See does decaf coffee have caffeine?
Coffee, stomach acid and heartburn
For most people, what coffee does in the stomach matters more than the pH of the drink. Caffeine increases the release of acid in your stomach, which sometimes leads to an upset stomach or heartburn (MedlinePlus). Coffee and other sources of caffeine are among the foods and drinks commonly linked to symptoms of gastroesophageal reflux disease (GERD) (NIDDK).
The research is mixed:
| Study | What it found |
|---|---|
| Meta-analysis of 15 case-control studies | No significant link between coffee and GERD overall (Kim et al., 2014) |
| Nurses' Health Study II, 48,308 women followed over time | More than 6 servings a day of coffee was linked to 34% higher risk of reflux symptoms than none; tea and soda showed similar links, while milk, water and juice did not. Replacing 2 servings a day of coffee with water was linked to slightly lower risk (Mehta et al., 2020) |
These are observational studies, so they show associations, not cause and effect. The practical takeaway is that coffee does not cause reflux in everyone, but it can make symptoms worse for some people.
If coffee bothers your stomach
- Drink less at a time. A smaller cup means less caffeine and less of the drink's acids.
- Have it with food rather than on an empty stomach, if you notice it bothers you more then. See can you drink coffee while fasting?
- Try a dark roast or a lower-caffeine option, knowing the evidence is limited.
- Swap one cup for water, which was linked to lower risk of reflux symptoms in the large study above (Mehta et al., 2020).
- Keep a simple log of what you drink and when symptoms happen, and share it with your provider.
- See a provider if you have heartburn often or symptoms that do not improve, and talk with your doctor about which foods and drinks to cut back (NIDDK).
Coffee can also speed things up in your gut; see why coffee makes you poop.
Common myths (quick reality check)
Myth: Coffee is extremely acidic. Reality: Coffee is mildly acidic, with a pH around 4.85 to 5.13 in one study, closer to neutral than strongly acidic liquids.
Myth: Cold brew is much less acidic. Reality: Cold brew and hot brew had comparable pH in a direct comparison, though hot brew had more total acid.
Myth: Decaf will fix coffee-related reflux. Reality: In a large study, links between coffee and reflux symptoms were similar for caffeinated and decaffeinated drinks.
Frequently asked questions (FAQ)
Is coffee acidic?
Yes, mildly. Hot and cold brew coffee had a pH of about 4.85 to 5.13 in one study, where 7 is neutral.
What is the pH of coffee?
About 4.85 to 5.13 for both hot and cold brew light roast coffee in a 2018 study. Beans, roast and brewing method can change it.
Is cold brew less acidic than hot coffee?
Not by pH. Cold and hot brew had comparable pH values, but hot brew had more total titratable acid.
Is decaf coffee acidic?
Yes. Decaf is still brewed from coffee beans, and in a large study reflux results were similar for caffeinated and decaffeinated drinks.
Why does coffee give me heartburn?
Caffeine increases stomach acid, which can lead to heartburn or an upset stomach. Coffee is also among the drinks commonly linked to reflux symptoms.
What coffee is easiest on the stomach?
There is no proven option. A small study found a dark roast stimulated less stomach acid than a medium roast; smaller cups and drinking coffee with food may also help.
Related guides
- Why does coffee make you poop?
- Does decaf coffee have caffeine?
- Can you drink coffee while fasting?
- How much caffeine is in a cup of coffee?
- Mushroom coffee side effects
Disclaimer and when to seek help
This article is for general education and is not medical advice. These statements have not been evaluated by the Food and Drug Administration. Our products are not intended to diagnose, treat, cure, or prevent any disease. Talk to your health care provider if you have frequent heartburn, reflux, ulcers or other stomach problems, are pregnant or breastfeeding, or take medication.
References
- U.S. Geological Survey, Water Science School. "pH and Water".
- Rao NZ, Fuller M. "Acidity and Antioxidant Activity of Cold Brew Coffee." Scientific Reports, 2018;8(1):16030. doi:10.1038/s41598-018-34392-w
- Rubach M, et al. "A dark brown roast coffee blend is less effective at stimulating gastric acid secretion in healthy volunteers compared to a medium roast market blend." Molecular Nutrition & Food Research, 2014;58(6):1370-1373. doi:10.1002/mnfr.201300890
- MedlinePlus (U.S. National Library of Medicine). "Caffeine".
- Kim J, et al. "Association between coffee intake and gastroesophageal reflux disease: a meta-analysis." Diseases of the Esophagus, 2014;27(4):311-317. doi:10.1111/dote.12099
- Mehta RS, Song M, Staller K, Chan AT. "Association Between Beverage Intake and Incidence of Gastroesophageal Reflux Symptoms." Clinical Gastroenterology and Hepatology, 2020;18(10):2226-2233. doi:10.1016/j.cgh.2019.11.040
- National Institute of Diabetes and Digestive and Kidney Diseases. "Eating, Diet, & Nutrition for GER & GERD".
