What causes acid reflux from the stomach?

Gastric acid reflux refers to the backward flow of gastric contents into the esophagus and up to the oropharynx. At this point, individuals perceive an acidic sensation in the mouth. Often, acid reflux occurs after meals or during nighttime and is accompanied by a burning sensation behind the sternum—commonly known as “heartburn.”

One major cause is pathological—such as gastric disorders triggered by gastric acid irritation, leading to heartburn and acid regurgitation. Conditions including gastritis, peptic ulcer disease, gastroesophageal reflux disease (GERD), and functional dyspepsia can all cause acid reflux. Additionally, some individuals taking nonsteroidal anti-inflammatory drugs (NSAIDs) or antipyretic-analgesic medications may experience gastric mucosal injury, resulting in acid reflux and heartburn. As GERD worsens, retrosternal pain may develop—sometimes mimicking cardiac symptoms—necessitating prompt medical evaluation to differentiate from heart disease.

The second category of contributing factors involves dietary habits—for example, overeating or consuming large meals rapidly, which 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 reflux and heartburn.

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