The truth is that smoking cigarettes may actually make heartburn worse. Smoking causes the lower esophageal sphincter (LES), which is located at the end of the esophagus, to weaken. The LES keeps stomach acid from backing up into the esophagus. When the LES is not functioning properly, stomach acid can come up into the esophagus and cause damage as well as heartburn.
Many adults may have the occasional bout of heartburn, but persistent heartburn could be a symptom of gastroesophageal reflux disease (GERD).
Source:
American College of Gastroenterology. "Heartburn Or Gastroesophageal Reflux Disease (GERD)." American College of Gastroenterology 2011. 26 Jan 2011.

