Heartburn is caused by the backflow (reflux) of stomach acid into the esophagus. Although many believe that reflux has to be extremely acidic in order to produce heartburn symptoms, recent research suggests that even mildly acidic reflux can cause heartburn in some individuals.

There are many dietary and lifestyle factors that may contribute to the development of reflux by:

• Promoting the relaxation of the lower esophageal sphincter (LES), which serves as a valve between the stomach and the esophagus. When the LES does not close properly, stomach acid may reflux into the esophagus.
  
  
• Increasing the amount of acid produced in the stomach.
  
  
• Increasing stomach pressure.
  
  
• Making the esophagus more sensitive to stomach acid.

Eating habits are believed to be among the most common contributing factors of heartburn. The condition has long been associated with the consumption of certain foods, including citrus fruits, chocolate, peppermint, tomatoes, raw onions, garlic, black pepper and fatty or spicy foods. Certain beverages, including coffee, tea, and caffeinated, carbonated and alcoholic beverages have also been linked to the development of heartburn. However, according to recent research, there is no evidence to suggest that avoiding such foods and beverages will help prevent or alleviate heartburn.

Heartburn has also been associated with eating too fast or eating less than two hours before bedtime.

Certain body positions can also contribute to heartburn. These include lying down, especially too soon after eating, and maneuvers that increase pressure on the abdomen, such as bending over and straining to pass stool.

Certain medical conditions can also contribute to heartburn, including:

• Pregnancy.
  
  
• Gastroesophageal reflux disease (GERD). A condition in which the stomach contents flow back (reflux) into the esophagus and damage its lining.
  
  
• Hiatal hernia. The protrusion of the stomach into the chest through a tear or weakness in the diaphragm.
  
  
• Diabetes. Diabetes can cause delayed emptying of the stomach (gastroparesis) which may lead to backflow of stomach contents into the esophagus.
  
  
• Gastritis. Inflammation of the inner lining of the stomach. The most common form of gastritis is erosive gastritis, in which acid and/or other factors inflame, damage and wear down the stomach lining.
  
  
• Peptic ulcers. Peptic ulcers occur when stomach acid and other digestive juices erode the inner lining of the stomach or first part of the small intestine.

Heartburn may also be related to certain medications (e.g., antibiotics, aspirin, ibuprofen) as well as the following lifestyle habits:

• Being overweight
• Smoking
• Stressful lifestyles
• Wearing tight clothing around the waist
• Exercise that increases pressure on the abdomen (e.g., running)