By now, you're probably aware of the many dangers of smoking, including life-threatening diseases such as cancer and emphysema. What you may not know, though, is what smoking does to your digestive system. Smoking affects all parts of the digestive tract, increasing your risk of everything from heartburn and peptic ulcers to Crohn's disease and possibly gallstones. Here's a rundown of potential conditions:

  • Heartburn. More than 50 million Americans experience symptoms of heartburn-a burning pain in the chest that usually occurs after eating-at least once a month and a staggering 15 million experience it every day. Heartburn is a symptom of gastroesophageal reflux disease (GERD), which occurs when acidic juices in the stomach flow backward into the esophagus. Normally, a muscular valve at the lower end of the esophagus, called the lower esophageal sphincter (LES), holds the acids in the stomach. Smoking weakens the LES, allowing stomach acid to flow into the esophagus. When stomach acid contacts the esophagus, the inner lining can become damaged.
  • Peptic ulcer. A peptic ulcer is a sore on the lining of the stomach or duodenum, which is the beginning of the small intestine. Research has shown that smokers are more likely to develop ulcers than nonsmokers. In addition, if people with an ulcer keep smoking, their ulcer may not heal. Smoking also raises the risk of infection from a bacterium called Helicobacter pylori and increases the risk of ulceration from alcohol and over-the-counter pain relievers.
  • Liver disease. The liver serves many functions, including processing drugs, alcohol and other toxins and removing them from the body. Research shows that smoking inhibits the liver's ability to process those substances and can worsen liver disease caused by alcohol abuse.
  • Crohn's disease. This disorder causes inflammation of the digestive tract, which can lead to myriad problems, including severe diarrhea, abdominal pain and cramping and ulcers. Research has found that both current and former smokers have a higher risk of developing Crohn's disease than nonsmokers. Smoking is linked with higher rates of relapse, repeat surgery and the need for drug therapy in Crohn's sufferers. Although exactly why smoking increases the risk for Crohn's disease is unknown, some researchers believe that smoking might lower the defenses of the intestines, decrease blood flow to the intestines or cause changes in the immune system that result in inflammation.

While some of the effects of smoking on the digestive system are short-lived once a person quits smoking, former smokers still remain at risk for developing Crohn's disease.