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Smoking and Your Digestive System

Dangers of smoking

Each year 400,000 people in the United States die from cigarette smoking. Smoking cigarettes causes life-threatening diseases. Lung cancer, emphysema (EM-fuh-ZEE-muh), and heart disease are some of these diseases. Smoking also causes digestive illnesses.

How smoking harms your digestive system

Smoking affects all parts of the body. When you smoke, changes take place in your digestive system. The digestive system converts foods into the nutrients the body needs to live. You can have serious problems when your digestive system changes.

For example, smoking helps cause heartburn and stomach (peptic) ulcers. Smoking makes your liver less able to handle drugs and alcohol. Smoking gives you greater chances of getting Crohn’s (CROW-nz) disease and gall stones. The digestive problems that smoking causes are enough reason to quit smoking.


Heartburn is very common. More than 60 million Americans have heartburn at least once a month. About 15 million get heartburn daily.

You get heartburn when acid juices from your stomach back up into your food pipe. The name of the food pipe is the esophagus (ee-SOFF-uh-gus). The esophagus runs from your mouth to your stomach. Normally, a valve at the lower end of the esophagus keeps acid from leaving the stomach. When you smoke, the valve gets weaker and allows stomach acid to flow backward into your esophagus. This flowing backward is called reflux (REE-flux).

Smoking also seems to move some bile salts from the intestine into the stomach. As a result, stomach acid is even more harmful. In addition, smoking can injure the esophagus itself. Your esophagus is then more easily damaged by reflux acid.

Peptic ulcer

A peptic (PEP-tik) ulcer is an open sore in the lining of the stomach. A peptic ulcer can also occur in the first part of the small intestine, which is called the duodenum (doo-AH-denum). Smoking and ulcers are related. Smoking seems to be one of several factors that work together to form ulcers. For example, smoking may increase your risk of infection with the bacteria that cause some peptic ulcers.

Stomach acid also plays a big role in producing ulcers. Normally, the food we eat decreases the harmful effects, or buffers, most acid in the stomach. Some acid remains unbuffered when it enters the small intestine. There, sodium (SO-dee-um) bicarbonate (bye-CARbun-ate) from the pancreas (PAN-kree-us) buffers the acid.

Some studies show that smoking reduces the amount of bicarbonate the pancreas makes. Acid then does not get buffered in the small intestine. Other studies show that smoking may increase the amount of acid in the stomach.

The 1989 Surgeon General’s report states that cigarette smokers are more likely than non smokers to get ulcers, especially in the duodenum. Smokers are more likely to have ulcers that do not heal, even with medical treatment. Smokers are also more likely to die from ulcers. The research strongly suggests that people with ulcers should quit smoking.

Liver disease

The liver is an important organ that has many tasks. Among other things, the liver processes drugs, alcohol, and other toxins to remove them from the body. Toxins are substances that are harmful to the body. Some studies show that smoking changes the liver’s ability to handle these substances. In some cases, the dose of medicine needed to treat an illness may also be affected.

Some research shows that smoking may worsen liver disease that is caused by too much alcohol use.

Crohn’s disease

Crohn’s disease inflames the lining of the intestines. The disease usually affects the small intestine, but can occur anywhere in the digestive tract. The main symptoms are pain and diarrhea. Studies show that both smokers and ex-smokers have more chance of getting Crohn’s disease than non-smokers do.

Smoking is related to more bouts of Crohn’s and the need for surgery. Women who are smokers or ex-smokers have a slightly higher risk than men do in all these areas.

The reason that smoking increases the risk of Crohn’s disease is not known. Some theories hold that smoking might lower the intestines’ defenses or decrease blood flow to the intestines. Other theories hold that smoking might cause changes in the immune system that inflame the intestines. 

Gall stones

Smoking may increase the risk of getting gall stones. The risk may be higher for women. Research is incomplete, and more study is needed.

Can the damage be reversed?

Some of the effects that smoking has on the digestive system seem to last a short time. For example, while a person is smoking, the pancreas produces less bicarbonate. A half-hour after smoking, the amount of bicarbonate returns to normal. The effects of smoking on how the liver handles drugs also disappear when a person quits smoking. However, people who no longer smoke are still at risk for Crohn’s disease.

Get help to quit smoking

UPMC Health System offers programs to help people quit smoking. Another name for quitting smoking is smoking cessation (sess-AY-shun). For help to quit smoking, call the UPMC Referral Service at 1-800-533-UPMC (8762).

Reviewed April 2011

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