Heartburn is caused primarily by stomach acid backing up into the esophagus, the tube that carries food from the mouth to the stomach. This happens when the lower esophageal sphincter (LES), a muscle that normally closes to keep stomach contents in place, weakens or relaxes inappropriately, allowing acid to leak upward and irritate the esophageal lining, causing a burning sensation

. Several factors can trigger or worsen heartburn, including:

• Dietary triggers: Acidic or high-fat foods such as citrus fruits, tomatoes, onions, chocolate, coffee, cheese, peppermint, spicy foods, and large meals

• Lifestyle factors: Smoking relaxes the LES, increasing reflux risk; wearing tight clothing, eating right before bed, and lying down or bending over after eating also contribute

• Physiological conditions: Being overweight or pregnant increases abdominal pressure, which can push stomach acid into the esophagus. Hormonal changes during pregnancy (e.g., increased progesterone) can also relax the LES

• Medical conditions: Hiatal hernia (where part of the stomach moves into the chest), certain medications (like aspirin, ibuprofen, sedatives, blood pressure drugs, and some antibiotics), stress, and motility disorders affecting esophageal function can cause or exacerbate heartburn

In summary, heartburn results from acid reflux due to LES dysfunction, with multiple dietary, lifestyle, physiological, and medical factors contributing to its onset and severity