What causes acid reflux from the stomach?

Gastroesophageal reflux—commonly referred to as “acid regurgitation”—occurs when gastric contents flow backward from the stomach into the esophagus and up to the oropharynx, resulting in a sour or acidic taste in the mouth. Acid reflux commonly occurs after meals and during nighttime, often accompanied by a burning sensation behind the sternum, known as “heartburn.”

The underlying causes fall into two main categories. First are pathological factors—for instance, gastric disorders triggered by excessive gastric acid secretion. This acid irritates the gastric mucosa, producing heartburn and acid regurgitation. Conditions such as gastritis, peptic ulcer disease, gastroesophageal reflux disease (GERD), and functional dyspepsia can all lead to acid reflux. Additionally, certain medications—including nonsteroidal anti-inflammatory drugs (NSAIDs) and antipyretic-analgesics—may damage the gastric mucosa and thereby provoke acid reflux and heartburn. As GERD worsens, patients may experience retrosternal pain, which can sometimes be mistaken for cardiac chest pain. In such cases, prompt medical evaluation is essential to allow physicians to accurately differentiate between gastrointestinal and cardiac causes.

The second category comprises dietary influences. For example, overeating or binge eating increases intragastric pressure. Particularly when lying down, gravity facilitates the reflux of gastric contents into the esophagus and subsequently into the oral cavity, causing acid regurgitation and heartburn.

We therefore recommend that affected individuals avoid overeating and instead consume meals to approximately 70–80% satiety. They should also refrain from lying down immediately after eating and avoid late-night dinners. Furthermore, smoking cessation is strongly advised, as nicotine relaxes the lower esophageal sphincter, thereby exacerbating reflux.