One of the main complaints many people seem to have when drinking coffee is that it causes stomach problems.
This is often attributed to the acidity of coffee, but what does this really mean? What is the pH of coffee? Here, we look at the science to see if acid is really the problem.
What is pH?
Your school chemistry classes might seem like a distant memory, so let’s just remind ourselves of what a few terms like “pH”, “acid” and “alkaline” mean.
Substances are either acid or alkaline, and this is measured on the pH scale. In practice, this scale runs from 0 to 14. Pure water is neutral, meaning it is neither acid nor alkaline, having a pH value of 7.
Anything less than 7 on the scale is an acid while anything above 7 is an alkaline. A substance with a pH value of 6 is considered mildly acidic; something with a pH value of 0 is highly acidic. A value of 8 on the pH scale indicates a mild alkaline substance and a value of 14, a strong alkaline.
Many foods and drinks are acidic. Here are some examples:
- Milk: pH6
- Bananas: pH5
- Apple juice pH4
- Orange juice, soda pH3
- Lemon Juice, vinegar pH2
Ok, so that’s the science bit done!
Acidity in coffee – what is the pH of coffee?
When we talk about “acidity” in coffee, there are actually several different meanings. Just like any other food or drink, coffee has a level of acidity in terms of a pH number. This may vary depending on certain factors, but in fact, the variation is not large.
Most sources will tell you that the pH of black coffee is around 5. This puts it in the same category as bananas – meaning it is much “acidic” according to its pH value than lemon juice, vinegar or orange juice.
As we mentioned, this number may vary slightly, but we’ll come back to that soon.
Acidity in coffee – the flavor profile
The second meaning of “acidity” when talking about coffee refers to the taste of the coffee rather than the pH value.
When we talk about the “acidity” of coffee in this way, it is usually a positive thing, something desirable. When we say a coffee displays “acidity”, it means it has a bright, sharp flavor.
Coffees with good acidity have complex flavor profiles and often display fruity or floral notes. These can be among the most sought-after coffees of all.
Where does this kind of acidity come from? There are many factors that may affect the acidity of the flavor profile of a coffee, but perhaps the most important is the altitude at which it is grown.
Coffees grown at higher altitudes tend to ripen more slowly, allowing more time for complex flavors to develop. On the other hand, low-grown coffees tend to be less acidic. Brazil, for example, is known as an origin that traditionally displays a low acidity.
Acidity – a cause of stomach problems?
Finally, when some people say that a coffee is “acidic”, what they really mean is that the coffee gives them digestive problems like heartburn and acid reflux.
While nobody is arguing that coffee causes these problems, is it really due to the pH level? Are pH level, acidity as part of the flavor profile and stomach problems really connected? Let’s have a look at this next.
An experiment was carried out that measured the pH value of three coffees, a low-acid Sumatran, a medium-acid Panamanian and a high-acid Kenyan. Sumatran coffees are famously low-acid, while Kenyans are reputed for their complex and tart acidity.
In the experiment, the pH level of these three coffees was measured and the result was as follows:
- Sumatra: pH4.6
- Panama pH4.5
- Kenya pH4.3
At first, these results would seem to bear out what we might intuitively expect. The coffee with the lowest acidity in the flavor was also the least acidic in terms of pH level, and vice versa.
However, if we look at the details more closely, we realize that the difference is minimal. A pH difference of on 0.2 between a high-acid coffee and a low-acid coffee is almost negligible in real terms.
According to our examples from earlier, this would still make all three coffee less acidic than the average cup of apple juice – and considerably less acidic than orange juice or lemon juice – and many other fruits.
The conclusion we can draw from this is that if you happily drink apple juice or orange juice without suffering any ill effects but find the “acidity” in coffee causes an adverse reaction in your stomach, then this is probably not due to the “acidity” (pH level) of coffee but something else.
Check out this video for more info about low-acid coffees.
If it’s not “acidity”, what is it?
So, if it’s not the acid in coffee that sets your stomach off, what is it? Of course, there’s another obvious culprit: caffeine.
Many people are sensitive to caffeine, and caffeine is known to stimulate the production of stomach acid. Could it be that it is the caffeine in coffee that is causing you trouble rather than the pH level of your brew?
Given that coffee is less acidic in terms of pH level than many other common foods, it would seem to be a reasonable assumption.
So what should you do?
If you want to test this out, it’s quite easy. Simply take a caffeine pill or drink a caffeinated energy drink – if this results in a similar reaction, you will have your answer.
If you discover you are sensitive to caffeine, or even if you want to try another way of avoiding heartburn or acid reflux from coffee, you might consider drinking low caffeine or decaf for a while.
In the end, this may prove more effective than seeking out “low acid” coffees – which may not even be significantly different in terms of pH anyway.
pH is not the whole story
What is the pH of coffee? We have established that it is about 5 – or perhaps slightly lower (more acidic) – but this doesn’t tell the whole story.
The pH of coffee is not the same as the sought-after acidity in the flavor profile of coffee and nor is it necessary to blame for coffee-related stomach troubles. If coffee upsets your stomach, perhaps it is the caffeine and not the “acidity” that is to blame after all.
Do you drink low-acid coffee? Or perhaps you drink decaf? How about adding milk? Do any of these work for you? If you have anything to add, please leave us a comment as we love to hear from you. And if you found our article useful, please don’t forget to share!
My name is Kathy Gallo, Editor of Ag Ferrari food blog. The guide you find here is designed exactly for you, and it is our hope that you find it not only interesting but also actionable.