Cold brew coffee, made by steeping grounds in cold water for many hours, is often promoted as a gentler alternative to traditional hot-brewed coffee. This slow, low-temperature process results in a smoother taste and is widely believed to be easier on the stomach. Despite its reputation for being low-acid, many people experience digestive discomfort, including pain, nausea, and reflux, after drinking it. Understanding the specific chemical and physiological factors at play explains why this beverage still causes trouble.
The Acidity Paradox
The primary selling point for cold brew is its lower acidity compared to coffee brewed with hot water. Hot water extraction pulls out more chlorogenic acids, converting them into stomach-irritating quinic acids. The cold steeping process avoids this chemical conversion, resulting in an acid profile many individuals find less harsh on the digestive system.
While cold brew has lower total titratable acidity, which contributes to the smoother flavor, the difference in pH level from hot coffee is often minor. Both cold and hot coffee typically fall within a pH range of 4.85 to 5.13, meaning cold brew remains an acidic beverage. For people with a sensitive stomach or a predisposition to Gastroesophageal Reflux Disease (GERD), this acidity level is still high enough to trigger symptoms.
The discomfort is not determined solely by the total amount of acid in the drink, but by how that acid interacts with the stomach lining. Any acidic beverage stimulates the stomach to produce more of its own hydrochloric acid. This interaction can irritate the stomach lining and potentially trigger a reflux episode.
Caffeine Concentration and Digestive Speed
A significant factor contributing to cold brew discomfort is the high concentration of caffeine in the finished product. Cold brew is often prepared as a potent concentrate meant to be diluted before drinking. If not adequately watered down, the resulting beverage can contain a much higher dose of caffeine per serving than standard hot coffee.
High concentrations of caffeine act as a strong pro-motility agent, dramatically stimulating the muscles of the digestive tract. This increased intestinal contraction can speed up the transit of contents through the gut, leading to cramping, spasms, or a laxative effect. Caffeine also directly affects the lower esophageal sphincter (LES), the muscular valve separating the esophagus from the stomach.
When the LES relaxes due to caffeine consumption, stomach acid can easily backflow into the esophagus. This causes the classic burning sensation known as heartburn or acid reflux. The sheer volume of caffeine in a typical cold brew serving can therefore be a more direct cause of digestive upset than the coffee’s acid level.
Non-Coffee Components That Irritate the Gut
Beyond the coffee itself, common additions used to customize cold brew can introduce significant digestive triggers. Many popular preparations include high-sugar syrups or artificial sweeteners. Artificial sweeteners, such as sugar alcohols, are poorly absorbed and can be fermented by gut bacteria, often resulting in gas and bloating.
For individuals with lactose intolerance, adding traditional dairy milk or cream is a common source of stomach pain, nausea, and intestinal distress. The lactose in dairy requires the enzyme lactase for proper digestion, and a deficiency in this enzyme is a widespread issue. Switching to a non-dairy alternative can immediately resolve this discomfort.
Another factor is the presence of coffee oils, known as diterpenes, which include cafestol and kahweol. Cold brew is an immersion-style method typically filtered through a mesh or coarse filter, much like a French press. Unlike drip coffee, which uses paper filters to trap these oily compounds, cold brew allows many diterpenes to pass into the final drink, and these oils can contribute to stomach irritation.
Strategies for Enjoying Cold Brew Comfortably
One of the most effective strategies to reduce cold brew discomfort is to ensure proper dilution of the concentrate before drinking. Increasing the water-to-concentrate ratio lowers the overall concentration of both caffeine and acidic compounds in the final cup. This simple adjustment can significantly lessen the stimulating effect on the gut and the LES.
Consuming cold brew alongside a meal, rather than on an empty stomach, can provide a buffer against the coffee’s acidity. Food helps dilute the coffee and absorbs some of the gastric acid the stomach produces in response to the beverage. This helps stabilize the stomach environment and minimize irritation.
To mitigate issues from additives, use unsweetened non-dairy alternatives, such as oat or almond milk, instead of traditional dairy products. If preparing cold brew at home, consider using a fine paper filter, rather than a standard mesh, during the final straining process. This technique helps remove more of the irritating coffee oils, resulting in a cleaner brew that is gentler on the stomach.