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How does smoking affect my stomach and bowel?

Stomach cancer

Smoking causes cancer of the stomach. Your risk of stomach cancer decreases after quitting, and after about 20 years it is approaching that of someone who has never smoked. Smoking is also associated with an increased risk of colorectal polyps and bowel cancer.

Peptic ulcer disease

Smoking causes peptic ulcer disease in people who also are infected with H.pylori, a common bacterial infection. Painful ulcers occur in the stomach and/or the duodenum (the part of the small intestine that connects to your stomach). Smoking is associated with increased risk for complications such as bleeding and perforated ulcers, and a greater risk of dying from the disease. Peptic ulcer disease can be treated, but it is somewhat less successful for people who continue to smoke.

Smoking has a number of effects on the stomach and gut that could promote the development of peptic ulcer disease. For example:

  • Smoking promotes the reflux of the duodenal contents back into the stomach.
  • Smoking increases the acidity of the duodenum and makes it more vulnerable to H.pylori infection.
  • Smoking constricts the small blood vessels in the stomach reducing blood flow. This can lead to damage of stomach tissues and slow down healing of ulcers.
  • Smoking reduces the production of natural substances that protect the stomach and duodenum from tissue damage.

Most of these effects do not last long and return to normal within minutes or hours after stopping smoking. This suggests that people who stop smoking have less risk of ulcers people who continue to smoke.

Crohn's disease

Smoking appears to increase the risk for Crohn's disease, a chronic inflammatory bowel condition. People with this disease suffer from pain, severe diarrhea, and intestinal bleeding. Treatment includes surgery to remove part of the bowel. Smokers with Crohn's disease are more likely to have more severe symptoms, and to have surgery earlier and more often than non-smokers.