Gastroesophageal reflux disease or GERD is caused by acid reflux. This means acid from the stomach flows back into the esophagus. It is quite normal to experience mild or moderate reflux once in a while. In fact, most people experience a little acid reflux at least twice or once a week. However, chronic GERD is a problem and requires treatment. Acid reflux can occur due to multiple reasons:

1. Malfunctioning esophagus
One of the common reasons is the malfunctioning of the lower esophageal sphincter (LES). The LES closes and opens the lower part of the esophagus. It blocks the contents of the stomachs from going up the food pipe.  Malfunctioning occurs when the LES relaxes. Other reasons include eating certain foods and taking certain medications.

2. Medications
The long-term use of certain medications increase the risk of GERD and acid reflux. Many often experience gastrointestinal side effects when they take nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofen, and naproxen. These medications can cause heartburn, esophageal irritation, peptic ulcers, and acid reflux. For people who already have GERD, the severity of symptoms is aggravated by these medicines. Certain prescription medications can also trigger acid reflux. These include calcium channel blockers, anticholinergics, beta-adrenergic agonists, and antihistamines. Additionally, medicines such as tricyclic antidepressants, prescription painkillers, and sedatives can cause indigestion and heartburn. The use of supplements such as iron and potassium have been also known to bring about acid reflux.

3. Obesity
Obesity causes additional pressure on the abdomen. The increased pressure makes digestion difficult. This relaxes the LES when it ideally should not. This may lead to acid going back up the esophagus, worsening the symptoms of GERD.

4. Smoking
Smoking is one of the major causes and risk factors of acid reflux. In the long-term, frequently breathing in secondhand smoke can also trigger GERD symptoms. Less saliva is produced due to the continuous inhalation of the chemicals present in tobacco. This slows down the digestion process and causes the stomach to empty out more slowly. As a result, more stomach acid is produced. This triggers the symptoms of acid reflux.

5. Digestive motility issues
During a normal digestive process, rhythmic contractions known as peristalsis moves the food through the digestive tract. This is known as digestive motility. The contractions may occur abnormally if a person has problems in digestive motility. The abnormality occurs due to two reason; one is that there is a problem in the muscles of the esophagus. Another reason could be a problem with the nerves or hormones controlling the contractions of the esophagus. Due to abnormalities in the peristalsis, there can be disruptions in the normal digestive process. This can lead to acid reflux.

6. Diet
Certain foods can trigger acid reflux symptoms such as heartburn and indigestion. These foods usually relax the LES or stimulate too much acid production. Fried and highly greasy foods have been known to cause acid reflux due to the relaxation of the LES. Other foods include high-fat meats, butter, margarine, mayonnaise, creamy sauces, and salad dressings. Dairy products made of whole milk, chocolate, peppermint, and caffeinated beverages can also trigger heartburn and indigestion. Food that produces too much acid includes spicy foods, black pepper, carbonated beverages, alcohol, tomato juice, and citrus fruits.