Why does coffee make me sick to my stomach?

In this short text we will provide the answer to the question: “Why does coffee make me sick to my stomach?”. In addition, we will discuss why coffee is bad for the stomach of some people and we will give you some tips on how to relieve the symptoms of stomach discomfort when drinking coffee. 

Why does coffee make me sick to my stomach?

Coffee contains certain compounds that can stimulate the production of gastric juice in the stomach, resulting in increased acidity (with a pH of 1-2). 

These compounds include chlorogenic acids, Nβ-alkanoil-5-hydroxytryptamine (C5HTs) found in coffee wax, and to a lesser extent, caffeine. It is believed that these compounds play a role in promoting the production of gastric juice.

Furthermore, there is a hypothesis that the roasting by-products of chlorogenic acid, such as pyrogallol, along with C5HTs, can irritate the gastric mucosa. (1)

The action of coffee on stomach acid secretion has raised the issue of a possible increase in dyspepsia (poor digestion, discomfort, nausea, heartburns, eructation, and flatulence), or esophageal burns, gastritis or ulcers, and gastro-esophageal reflux disease (GERD). (2)

Can coffee cause gastritis?

Coffee does not cause gastritis, but it should be avoided when we have gastritis. 

Gastritis is a disease that is characterized by inflammation of the gastric mucosa, which is the inner layer of the stomach’s lining.

Gastric lesions can arise from disruptions in stomach homeostasis at a local level. However, it is important to recognize the significant role played by centrally mediated processes in the development of these lesions. 

In fact, these centrally mediated processes are notable contributors to certain gastric lesions induced by stress. (2)

Gastritis has been considered as an acid-related disease. Therefore, it is easy to conceive that coffee containing caffeine stimulates the gastric acid production, and consequently increases the risk of these disorders. 

It has been repeatedly reported that coffee is a risk factor for both gastric and duodenal ulcers. However, there is no significant association between coffee intake and gastritis or ulcer diseases. (3)

Can coffee cause Gastro-Esophageal Reflux (GERD)?

Coffee has been hypothesized to diminish basal lower esophageal sphincter pressure, which would lead to gastroesophageal reflux and heartburn, but this is not reported by all studies. The most commonly reported cause of GERD is obesity. 

GERD is an unpleasant reflux condition caused by the return of the acid stomach content into the esophagus.(2)

There is no significant association between coffee intake and the incidence of GERD, although some past studies have reported that coffee intake may predispose to GERD syndrome. 

Besides the stimulating effect upon gastric acid production, it was also reported that coffee intake relaxes the lower esophageal sphincter, which might cause the chronic gastric acid reflux. 

Excessive secretion of gastric acid can damage not only the gastroduodenal but also esophageal mucosa, but there was no detection of a significant association between coffee consumption and GERD. (3)

Can coffee cause Functional Dyspepsia?

Patients with dyspepsia (FD) are advised to avoid drinking alcohol and coffee,  smoking, and aspirin and non-steroidal anti-inflammatory drugs, but it remains controversial whether these factors, and mainly coffee, may causally relate to the disease. 

Functional dyspepsia applies to recurring signs and symptoms of indigestion that have no obvious cause.(2)

The majority of studies focusing on FD and diet consist of analyzing multiple dietary items, including coffee because some believe that coffee consumption is associated with various dyspepsia symptoms. (4)

Drawing definitive conclusions regarding the correlation between coffee consumption and the occurrence of gastrointestinal symptoms is challenging due to the common practice of consuming coffee alongside or after meals.

This makes it difficult to isolate the precise impact of coffee alone on these symptoms.

In fact, some authors have reached the conclusion that due to conflicting data and the unclear nature of the relationship between gastrointestinal symptoms and coffee consumption, it is not advisable to routinely recommend avoiding coffee consumption for individuals experiencing such symptoms. (2)

Does coffee acidity and pH levels contribute to stomach discomfort ?

No, the pH level of a brewed coffee typically falls within the mildly acidic range. In robusta coffees, it usually fluctuates between 5.8 and 5.5, while fresh lightly roasted acidic arabica coffees tend to have a pH range of 4.3 to 4.8. 

Dark roasted blends typically have a slightly higher pH of around 5.0. It’s important to note that these pH levels are significantly higher than those of gastric juice and other acidic beverages like apple juice (pH 4.3–3.3) or citric juice (pH 2.3–3.3). (1) 

What can be done to relieve coffee stomach discomfort ?

Certain pre-roasting technological methods have been developed with the intention of reducing the occurrence of heartburn associated with coffee consumption. 

However, it is important to note that there are currently no clinical studies that have definitively demonstrated the effectiveness of these treatments in humans.

One approach to mitigate heartburn involves reducing the coffee wax content, thereby decreasing the levels of C5HTs. 

This reduction can be achieved through steam treatment, either as an independent process or as a component of water or CO2 decaffeination methods. 

It is worth mentioning that these methods not only help reduce C5HTs but also contribute to lowering the content of chlorogenic acids and caffeine in coffee. (1)


In this short text we provided the answer to the question: “Why does coffee make me sick to my stomach?”. In addition, we discussed why coffee is bad for the stomach of some people and we gave you some tips on how to relieve the symptoms of stomach discomfort when drinking coffee.


  1. Farah, Adriana.  Nutritional and health effects of coffee. 10.19103/AS.2017.0022.14. 2018.
  2. Nehlig A. Effects of Coffee on the Gastro-Intestinal Tract: A Narrative Review and Literature Update. Nutrients. Jan 17;14(2):399. 2022.
  3. Shimamoto T, Yamamichi N, Kodashima S, Takahashi Y, Fujishiro M, Oka M, Mitsushima T, Koike K. No association of coffee consumption with gastric ulcer, duodenal ulcer, reflux esophagitis, and non-erosive reflux disease: a cross-sectional study of 8,013 healthy subjects in Japan. PLoS One. 12;8(6):e65996. 2013.
  4. Correia, H., Peneiras, S., Levchook, N., Peneiras, E., Levchook, T., & Nayyar, J. Effects of a non-caffeinated coffee substitute on functional dyspepsia. Clinical Nutrition ESPEN. 2020.

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