New research shows that smoking greatly increases a person's risk of acid reflux.

Eating a diet high in salt also increases the risk. But coffee, tea and alcohol -- once thought to also exacerbate the condition -- were found to have little impact, researchers said.

The study was based on data from more than 40,000 people. Those who smoked every day for more than 20 years were 70 percent more likely to have acid reflux than non-smokers.

Acid reflux is a very common disorder and one of the most frequent causes of indigestion.

Researchers note that regular consumption of bread high in fiber and at least 30 minutes of exercise once a week each cut in half the risk of reflux.

The study shows that heavy coffee drinkers were 40 percent less likely to develop acid reflux than those who were light coffee drinkers. But researchers said people with acid reflux -- who might not drink coffee -- could have impacted the results.