There are scientific studies both pro and con on whether coffee causes heartburn or not. However, many people do experience chest pain after drinking coffee.
But is this heartburn or something else? And if it is heartburn, can coffee be the trigger?
In order to understand how researchers are studying the connection between heartburn and coffee, let’s start with a very short overview of acid reflux:
Acid reflux 101
There is a muscle between the food pipe and the stomach, called the lower esophageal sphincter or LES.
This muscle is responsible for preventing stomach content from backing up into the esophagus. When the LES is tight, nothing from the stomach can enter the food pipe.
When the LES is relaxed, digestive juices can seep back into the food pipe and cause all kinds of problems. The most typical symptom is the irritation of the lining of the food pipe by the stomach acids. This causes a burning sensation around the center of the chest, called heartburn.
This is something we don’t know for sure. There are risk factors like:
- hiatal hernia
- certain foods (fatty, sugary foods, alcohol, chocolate, etc.)
- lack of physical exercise
The more risk factors apply to you, the more likely to experience acid reflux episodes.
The bottom line is that a relaxed LES seems to be the direct cause of acid reflux.
Research on coffee and heartburn
Since coffee is a very popular drink and acid reflux is a fairly common health issue (nearly a third of US adults experience acid reflux weekly), the relation between coffee and acid reflux is being heavily researched.
Scientists usually use one of these methods:
- they ask people to eat or drink certain foods and measure the LES pressure
- they ask what people eat and how often they experience heartburn or other reflux symptoms
Effect of caffeine on LES pressure
Studies that measure the LES pressure after drinking coffee or some other form of caffeine intake, usually find that coffee relaxes the LES:
This study indicated that caffeine 3.5 mg/kg affected esophageal function, resulting in a decrease in basal LES pressure and distal esophageal contraction, which is known to promote the reflux of gastric contents up into the esophagus.(source)
Thus, coffee at either pH 4.5 or 7.0 caused a decrease in fasting and postcibal lower esophageal sphincter pressure in normal volunteers and patients with reflux esophagitis. The magnitude and the duration of the effect were greater after coffee at the lower pH. These data support the clinical belief that coffee may cause or aggravate heartburn by decreasing lower esophageal sphincter pressure.(source)
This suggests, that coffee might trigger acid reflux and therefore cause heartburn.
Coffee & heartburn surveys
This type of research includes questionnaires and meta-analysis of other studies.
Results are contradictory, some studies suggest a connection between coffee and heartburn, while others find coffee does not trigger or aggravate heartburn:
Frequent consumption of carbonated drinks […] and frequent consumption of tea or coffee […] were significantly associated with a diagnosis of GERD.(source)
Note interesting finding in the study below: coffee did trigger heartburn, but caffeine itself did not, which seems to match the findings of this study.
Coffee, in contrast to tea, increases gastro-oesophageal reflux, an effect that is less pronounced after decaffeination. Caffeine does not seem to be responsible for gastro-oesophageal reflux which must be attributed to other components of coffee.(source)
In an analysis of data from the prospective Nurses’ Health Study II, intake of coffee, tea, or soda was associated with an increased risk of GER symptoms. In contrast, consumption of water, juice, or milk was not associated with GER symptoms. Drinking water instead of coffee, tea, or soda reduced the risk of GER symptoms.(source)
And now a few studies that found no relation between coffee and heartburn:
Drinking coffee or tea and adding milk or sugar was not associated with reflux symptoms or EE.(source)
In subgroup analyses in which the groups were subdivided based on the amount of coffee intake, quality of study, and assessment of exposure, there was no significant association between coffee intake and GERD.(source)
Tobacco smoking and table salt intake seem to be risk factors for gastro-oesophageal reflux symptoms. Dietary fibres and physical exercise may protect against reflux. Alcohol, coffee, and tea do not seem to be risk factors for reflux.(source)
Does coffee cause acid reflux?
While this is still debated, it looks like coffee is definitely a risk factor for many people. However, the exact mechanism of how coffee triggers heartburn is unclear.
Some of the above-linked studies found that coffee-related gastrointestinal problems are probably not caused by caffeine content.
This study found that regular coffee and decaffeinated coffee increased stomach acid secretion much more than caffeine alone.
Drinking coffee on an empty stomach in the morning can also cause problems:
- increases your cortisol level
- interferes with the blood sugar level
- stimulates stomach acid secretion and therefore might cause acid reflux
Looks like coffee is an acid reflux risk factor for two reasons:
- it might relax the LES
- increases the production of stomach acids
Is your heartburn really triggered by coffee?
Many people like to drink a cup of coffee after a large meal. Experiencing heartburn shortly after might feel like it was triggered by the coffee.
What else can cause heartburn after coffee?
Heartburn is not the only reason for experiencing chest pain after drinking coffee.
Some other possible causes are:
- Problems in the digestive tract: e.g. gallbladder disease, pancreatitis can both cause stomach and chest pain.
- Esophageal spasms: drinking too hot or too cold beverages can trigger esophageal spasms, chest pain is a typical symptom.
- Heart issues: this is not as common as many people think. When consumed in moderation, coffee is unlikely to trigger heart problems for healthy adults. On the contrary, coffee might decrease the risk of heart failure.
- Caffeine allergy: albeit chest pain is not a typical allergic reaction, sometimes food allergy might be the cause.
If you want to know more, check out our article about chest pain after drinking coffee here.
Does decaf coffee cause heartburn?
Looks like caffeine is not responsible for causing heartburn, it is some other ingredient in the coffee.
Despite the mixed results of scientific studies, coffee is believed to be a common trigger of acid reflux symptoms.
If coffee causes you heartburn, you might want to reduce your consumption or eliminate it from your diet.
However, sometimes it’s not the coffee that triggers chest pain and other symptoms. Both sugar and milk might trigger acid reflux symptoms.