Normally, acid is kept in your stomach by a muscular valve called the esophageal sphincter. However, if this valve is weakened or if you overeat, acid can flow up into your esophagus. An over-stretched stomach causes the esophageal sphincter to open, allowing stomach acid to flow up. Citrus fruits, orange juice and tomato sauce can irritate the esophagus, increasing symptoms. Tight belts or clothes can push acid up.
Gravity helps keep stomach acid in the stomach.
If heartburn continues to be a daily problem, consult with your physician. You may need prescription medications or surgery to avoid long-term complications.