Gastroesophageal Reflux Disease (GERD), commonly known as acid reflux, affects a significant portion of the population, causing discomfort when stomach contents flow back into the esophagus. For many individuals who experience this condition, the daily ritual of drinking coffee is a direct trigger for their symptoms. Understanding why this happens involves looking beyond the simple acidity of the beverage and examining the specific chemical compounds and physiological reactions it provokes. This article explains the mechanisms by which coffee exacerbates acid reflux and offers practical ways to enjoy your brew with less irritation.
Specific Compounds in Coffee That Cause Irritation
Coffee beans contain chemical substances that interact with the digestive system. The two primary irritants are organic acids and the stimulant, caffeine.
Chlorogenic acids (CGAs) are the most abundant organic acids in coffee. These acids, along with their breakdown products, irritate the sensitive stomach lining and contribute to the beverage’s acidic load. Lighter roasted coffees retain higher concentrations of CGAs, which can feel harsher on a sensitive stomach.
The roasting process alters the bean’s chemical makeup. As the roast darkens, the concentration of CGAs significantly decreases due to thermal degradation. Darker roasts also produce higher levels of N-methylpyridium (NMP), which may help reduce the stomach’s natural acid secretion. However, the irritating effects of other compounds, including caffeine, often outweigh this minor protective effect.
How Coffee Affects the Esophageal Sphincter and Acid Production
Acid reflux occurs when stomach acid backs up into the esophagus. Coffee contributes to this problem through a dual mechanism: relaxing the valve that normally prevents reflux and stimulating the production of more stomach acid.
The Lower Esophageal Sphincter (LES) is a ring of muscle between the esophagus and the stomach that normally closes tightly to keep acid out. Caffeine is a known relaxant of the LES, causing a sustained decrease in its pressure shortly after consumption. When the LES pressure drops, the valve loosens, creating a pathway for acidic stomach contents to splash back up.
Coffee also triggers the stomach to generate more gastric acid. Caffeine interacts with Type 2 Bitter Receptors (TAS2R) in the stomach lining. This stimulates G cells to release the hormone gastrin, which signals parietal cells to increase the secretion of hydrochloric acid. This dramatically increases the volume of corrosive fluid available for reflux.
Even decaffeinated coffee can stimulate acid secretion, suggesting that non-caffeine compounds are also involved in the gastric response. This increase in acid production occurs independent of the LES relaxation caused by caffeine. The combination of a relaxed LES and increased stomach acid creates the perfect environment for acid reflux.
Modifying Your Coffee Habit to Minimize Symptoms
Individuals who experience reflux do not need to eliminate coffee entirely; several adjustments can minimize the irritating effects. One effective strategy is switching to a darker roast, such as a French or Italian roast. Since the intense heat breaks down chlorogenic acids and increases acid-reducing NMP, dark roasts may be gentler on the stomach than lighter roasts.
The method of preparation also plays a significant role in reducing irritating compounds. Cold brewing involves steeping coffee grounds in cool water for an extended period. This process can reduce the total concentration of acids by as much as 67% compared to hot brewing, resulting in a smoother, less irritating beverage.
The type of filter used can also help remove oils that contribute to digestive upset. Paper filters are effective at trapping acidic oils and diterpenes that metal filters, like those used in a French press, allow to pass.
Avoiding coffee consumption on an empty stomach is a practical step, as food acts as a buffer against high concentrations of coffee compounds. Consider the additions you make to your coffee, as certain ingredients can help neutralize some acidity. Adding a splash of low-fat dairy or a plant-based creamer can increase the overall pH of the beverage.