Question: What Causes GERD?
Answer: Gastroesophageal Reflux Disease (GERD) is caused by reflux of stomach acid into the esophagus. In most sufferers this is due to a relaxation of the lower esophageal sphincter (LES) that opens to allow food and liquids to pass into the stomach, and closes to prevent food and stomach acid from flowing back into the esophagus. This relaxation of the LES happens a few times each day in people without GERD. It’s not known why it happens more frequently in GERD patients. The esophagus lining isn’t the same as that of the stomach and isn’t able to cope with acid as well as the stomach and is easily injured. It is this reflux of acid into the esophagus that produces the symptoms and potential damages to the esophagus.

Question: What Causes GERD?
Answer: Gastroesophageal Reflux Disease (GERD) is caused by reflux of stomach acid into the esophagus. In most sufferers this is due to a relaxation of the lower esophageal sphincter (LES) that opens to allow food and liquids to pass into the stomach, and closes to prevent food and stomach acid from flowing back into the esophagus. This relaxation of the LES happens a few times each day in people without GERD. It’s not known why it happens more frequently in GERD patients. The esophagus lining isn’t the same as that of the stomach and isn’t able to cope with acid as well as the stomach and is easily injured. It is this reflux of acid into the esophagus that produces the symptoms and potential damages to the esophagus.

A hiatal hernia may also contribute to acid reflux. A hiatal hernia occurs when the upper part of the stomach is above the diaphragm, the muscle wall that separates the stomach from the chest. The diaphragm helps the LES keep acid from coming up into the esophagus. When a hiatal hernia is present, it is easier for the acid to come up. In this way, a hiatal hernia can cause reflux. A hiatal hernia can happen in people of any age; many otherwise healthy people over 50 have a small one.

Other factors that may contribute to GERD include:
• alcohol use
• overweight
• pregnancy
• smoking

Also, certain foods can be associated with reflux events, including:
• citrus fruits
• chocolate
• drinks with caffeine
• fatty and fried foods
• garlic and onions
• mint flavorings
• spicy foods
• tomato-based foods, like spaghetti sauce, chili, and pizza

Source : http://heartburn.about.com/cs/gerdacidreflux/f/gerd_causes.htm