We’ve all heard that smoking increases the risk of many life-threatening diseases—including lung cancer, emphysema, and heart disease. But did you know that smoking also contributes to many cancers and diseases of the digestive system? Estimates show that about one-fifth of all adults smoke, and each year at least 443,000 Americans die from diseases caused by cigarette smoking.
Smoking has been found to increase the risk of cancers of the:
Research also suggests that smoking may also increase the risk of cancers of the liver, colon and rectum.
What are the other harmful effects of smoking on the digestive system?
Smoking contributes to heartburn, gastroesophageal reflux disease (GERD), peptic ulcers, and some liver disease. Smoking increases the risk of Crohn’s disease, colon polyps, and pancreatitis, and it may increase the risk of gallstones.
Heartburn is the painful, burning feeling in the chest caused by reflux. Smoking weakens the lower esophageal sphincter, the muscle between the esophagus and stomach that keeps stomach contents from flowing back into the esophagus. This causes heartburn and can possibly damage the lining of the esophagus.
GERD is persistent reflux can can lead to serious problems such as bleeding ulcers of the esophagus, narrowing of the esophagus that causes food to get stuck, and changes in the esophageal cells that can lead to cancer.
Smoking increases the risk of peptic ulcers. Peptic ulcers are sores on the inside lining of the stomach. The two most common causes of peptic ulcers are infection with a bacterium called Helicobacter pylori (H. pylori) and long-term use of nonsteroidal anti-inflammatory drugs such as aspirin and ibuprofen.
Studies suggest that smoking increases the risk of H. Pylori infection, slows the healing of peptic ulcers, and increases the likelihood that peptic ulcers will recur. Smoking increases the production of substances that may harm the lining of the stomach and the duodenum (the first part of the small intestine). Smoking also decreases factors that protect or heal the lining including:
- Blood flowing to the lining
- Secretion of mucus, a clear liquid that protects the lining from acid
- Production of sodium bicarbonate, a salt-like substance that neutralizes acid, by the pancreas.
The liver is the largest organ in the digestive system. The liver carries out many functions, such as making important blood proteins and bile, changing food into energy, and filtering alcohol and poisons from the blood. Research has shown that smoking harms the liver’s ability to process medications, alcohol, and other toxins and remove them from the body. In some cases, smoking may affect the dose of medication needed to treat an illness.
Smoking may worsen some liver diseases, including:
- primary biliary cirrhosis, a chronic liver disease that slowly destroys the bile ducts in the liver
- nonalcoholic fatty liver disease (NAFLD), a condition in which fat builds up in the liver
Current and former smokers have a higher risk of developing Crohn’s disease than people who have never smoked.
Crohn’s disease is an inflammatory bowel disease that causes irritation in the GI tract. The disease, which typically causes pain and diarrhea, most often affects the lower part of the small intestine; however, it can occur anywhere in the GI tract. The severity of symptoms varies from person to person, and the symptoms come and go. Crohn’s disease may lead to complications such as blockages of the intestine and ulcers that tunnel through the affected area into surrounding tissues. Medications may control symptoms. However, many people with Crohn’s disease require surgery to remove the affected portion of the intestine.
Among people with Crohn’s disease, people who smoke are more likely to:
- have more severe symptoms, more frequent symptoms, and more complications
- need more medications to control their symptoms
- require surgery
- have symptoms recur after surgery
The effects of smoking are more pronounced in women with Crohn’s disease than in men with the disease.
Researchers are studying why smoking increases the risk of Crohn’s disease and makes the disease worse. Some researchers believe smoking might lower the intestines’ defenses, decrease blood flow to the intestines, or cause immune system changes that result in inflammation. In people who inherit genes that make them susceptible to developing Crohn’s disease, smoking may affect how some of these genes work.
People who smoke are more likely to develop colon polyps. Colon polyps are growths on the inside surface of the colon or rectum. Some polyps are benign, or noncancerous, while some are cancerous or may become cancerous.
Among people who develop colon polyps, those who smoke have polyps that are larger, more numerous, and more likely to recur.
Smoking increases the risk of developing pancreatitis. Pancreatitis is inflammation of the pancreas, which is located behind the stomach and close to the duodenum. The pancreas secretes digestive enzymes that usually do not become active until they reach the small intestine. When the pancreas is inflamed, the digestive enzymes attack the tissues of the pancreas.
Some studies have shown that smoking may increase the risk of developing gallstones. However, research results are not consistent and more study is needed.
Gallstones are small, hard particles that develop in the gallbladder, the organ that stores bile made by the liver. Gallstones can move into the ducts that carry digestive enzymes from the gallbladder, liver, and pancreas to the duodenum, causing inflammation, infection, and abdominal pain.
It’s never too late to quit!
Quitting smoking can reverse some of the effects of smoking on the digestive system. For example, the balance between factors that harm and protect the stomach and duodenum lining returns to normal within a few hours of a person quitting smoking. The effects of smoking on how the liver handles medications also disappear when a person stops smoking. However, people who stop smoking continue to have a higher risk of some digestive diseases, such as colon polyps and pancreatitis, than people who have never smoked.
Quitting smoking can improve the symptoms of some digestive diseases or keep them from getting worse. For example, people with Crohn’s disease who quit smoking have less severe symptoms than smokers with the disease.