A burp, also known as belching or eructation, is the expulsion of gas from the upper digestive tract through the mouth. It is a normal physiological process that helps relieve discomfort from gas buildup.
Air’s Entry into the Digestive System
The primary source of gas leading to a burp is swallowed air, a process medically termed aerophagia. This occurs whenever a person eats, drinks, or even talks, as small amounts of air are inadvertently ingested along with food and liquids. Eating or drinking too quickly can significantly increase the amount of swallowed air.
Other common behaviors also contribute to aerophagia, such as talking while eating, chewing gum, or sucking on hard candies. Drinking carbonated beverages introduces additional gases directly into the digestive system. Mouth breathing, snoring, or using certain medical devices like CPAP machines can also lead to increased air swallowing. This swallowed air then collects in the stomach, creating pressure that eventually needs to be released.
The Physiological Process of Burping
When air accumulates in the stomach, it increases the gastric volume, activating receptors in the stomach wall. This initiates a reflex that causes the lower esophageal sphincter (LES) to relax. The LES, a muscle at the junction of the esophagus and stomach, typically remains contracted to prevent stomach contents from flowing back up. This relaxation, often referred to as a transient LES relaxation (TLESR), allows the trapped air to move upward from the stomach into the esophagus.
Once the air distends the esophagus, a second reflex triggers the relaxation of the upper esophageal sphincter (UES). The UES is another muscular valve located between the esophagus and the throat. With both sphincters relaxed, the air can then pass from the esophagus, through the throat, and out of the mouth. The characteristic sound of a burp is produced by the vibration of either the UES or the soft palate as the air is expelled.
The expulsion of air is often aided by the coordinated action of the diaphragm and abdominal muscles. These muscles can contract, increasing pressure within the abdomen and esophagus, which helps to push the gas upward and out.
Everyday Burping Triggers
Several everyday factors can increase the likelihood of burping by contributing to gas accumulation in the digestive system. Carbonated beverages contain dissolved carbon dioxide gas that gets released in the stomach. Rapid eating or drinking causes individuals to swallow more air.
Certain foods are known to produce gas during digestion, such as beans, lentils, and cruciferous vegetables like broccoli and cabbage. These foods contain complex sugars and fiber that are fermented by gut bacteria, generating gas. Anxiety or nervousness can also trigger more frequent burping, as people tend to swallow more air as a nervous habit. Poorly fitting dentures can also cause individuals to swallow excess air while eating and drinking.