Heartburn, also known as acid reflux or Gastroesophageal Reflux Disease (GERD), is a common digestive issue often triggered by various foods and beverages. For many, coffee is a beloved ritual that unfortunately leads to uncomfortable symptoms. The dilemma is whether changing the preparation method—specifically switching to iced coffee or cold brew—can offer relief. Understanding the science behind coffee’s interaction with the digestive system is the first step in finding a stomach-friendly solution.
How Coffee Triggers Acid Reflux
Coffee triggers acid reflux symptoms through two main physiological mechanisms. The first factor is the effect of caffeine, which relaxes the Lower Esophageal Sphincter (LES). The LES is a ring of muscle acting as a valve between the esophagus and the stomach; its relaxation allows stomach acid to flow back up, causing the burning sensation.
Beyond caffeine, other compounds in coffee stimulate the stomach to produce more acid. Research suggests the issue is related to the stimulation of gastric acid secretion, not just coffee’s inherent acidity. Specific compounds, such as N-alkanoyl-5-hydroxytryptamides, signal the stomach’s cells to increase the output of hydrochloric acid. This increased volume of stomach acid is more likely to cause irritation and reflux.
The Chemical Difference Between Hot Brew and Cold Brew
The term “iced coffee” often refers to hot-brewed coffee poured over ice, which does not change the chemical composition established during hot water extraction. True cold brew, in contrast, is made by steeping coffee grounds in cold or room-temperature water for an extended period, typically 12 to 24 hours. This difference in temperature and time dramatically alters the chemical extraction profile.
Hot water is an effective solvent that rapidly extracts a wide range of compounds, including acidic chlorogenic acids. These acids break down readily into quinic and caffeic acids during hot brewing, contributing to the perceived acidity and flavor. Because cold brewing uses time instead of heat, it extracts significantly fewer of these acidic compounds from the coffee grounds.
Cold brew coffee is measurably less acidic than hot-brewed coffee, sometimes by as much as 70% in terms of total titratable acids. While the final pH values of hot and cold brew can sometimes be similar, cold brew has a lower concentration of total acids. This lower concentration is often the source of relief for sensitive individuals, as it results from a gentler extraction of irritant acids.
Practical Adjustments for Coffee Drinkers
Individuals who still experience symptoms after switching to cold brew have several other adjustments they can make. The roast level plays a significant role in the concentration of reflux-triggering compounds. Darker roasts are generally recommended because the prolonged roasting process breaks down more chlorogenic acids than in light roasts.
Darker roasts also produce N-methylpyridinium (NMP), which potentially down-regulates gastric acid secretion. This compound is formed during the high-heat roasting process and is found in greater amounts in dark roast beans. Choosing a dark roast provides a double benefit by reducing irritant acids and generating a protective compound.
The timing and additions to the coffee also influence symptom severity. Consuming coffee with a meal can be beneficial, as drinking it on an empty stomach may increase acid irritation. Certain additives exacerbate reflux, such as high-fat creamers that slow down stomach emptying and increase pressure on the LES. Opting for low-fat milk or non-dairy alternatives may help buffer the coffee’s acidity.