Acid reflux is the result of a malfunctioning lower esophageal sphincter (LES). The LES is a small ring of muscles between the esophagus and stomach. When functioning correctly, it opens to allow food and fluid to pass down into the stomach, and then closes promptly. Acid is not supposed to flow upward — and when it does, reflux.
Reflux can also be contributed to by having a hiatal hernia. There is some evidence that there is a genetic component to reflux. Habits, however, are the main culprit. Being overweight, eating meals that are too large, and eating and drinking the wrong foods can all lead to reflux. Smoking is also a trigger.
The following consumables can lead to reflux:
Carbonated beverages
Citrus fruits
Fatty or fried foods
Spicy food
In short, diet and lifestyle are usually the factors behind reflux. Change them, and you'll likely change your symptoms.