HEARTBURN CAUSES

A number of different factors may contribute to LES malfunction with its consequent gastroesophageal acid reflux:

The eating of large meals that distend the stomach can cause the LES to open inappropriately.
Lying down within two to three hours of eating can cause the LES to open.
Obesity, pregnancy, and tight clothing can impair the ability of the LES to stay closed by putting pressure on the abdomen.
Certain drugs, notably nicotine, alcohol, diazepam (Valium), meperidine (Demerol), theophylline, morphine, prostaglandins, calcium channel blockers, nitrate heart medications, anticholinergic and adrenergic drugs (drugs that limit nerve reactions), including dopamine, can relax the LES.
Progesterone is thought to relax the LES.
Greasy foods and some other foods such as chocolate, coffee, and peppermint can relax the LES.
Paralysis and scleroderma can cause the LES to malfunction.
Hiatus hernia may also cause heartburn according to some gastroenterologists. (Hiatus hernia is a protrusion of part of the stomach through the diaphragm to a position next to the esophagus.).