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Cigarette smoking causes a variety of life-threatening diseases, including
lung cancer, emphysema, and heart disease. An estimated 430,000 deaths each year
are directly caused by cigarette smoking. Smoking is responsible for changes in
all parts of the body, including the digestive system. This fact can have
serious consequences because it is the digestive system that converts foods into
the nutrients the body needs to live.
Current estimates indicate that about one-third of all adults smoke. And,
while adult men seem to be smoking less, women and teenagers of both sexes seem
to be smoking more. How does smoking affect the digestive system of all these
people?
Harmful effects
Smoking has been shown to have harmful effects on all parts of the digestive
system, contributing to such common disorders as heartburn and peptic ulcers. It
also increases the risk of Crohn's disease and possibly gallstones. Smoking
seems to affect the liver, too, by changing the way it handles drugs and
alcohol. In fact, there seems to be enough evidence to stop smoking solely on
the basis of digestive distress.
Heartburn
Heartburn is common among Americans. More than 60 million Americans have
heartburn at least once a month, and about 15 million have it daily.
Heartburn happens when acidic juices from the stomach splash into the
esophagus. Normally, a muscular valve at the lower end of the esophagus, the
lower esophageal sphincter (LES), keeps the acid solution in the stomach and out
of the esophagus. Smoking decreases the strength of the esophageal valve,
thereby allowing stomach acids to reflux, or flow backward into the esophagus.
Smoking also seems to promote the movement of bile salts from the intestine
to the stomach, which makes the stomach acids more harmful. Finally, smoking may
directly injure the esophagus, making it less able to resist further damage from
refluxed fluids.
Peptic ulcer
A peptic ulcer is an open sore in the lining of the stomach or duodenum, the
first part of the small intestine. The exact cause of ulcers is not known. A relationship
between smoking cigarettes and ulcers, especially duodenal ulcers, does exist.
The 1989 Surgeon General's report stated that ulcers are more likely to occur,
less likely to heal, and more likely to cause death in smokers than in
nonsmokers.
Why is this so? Doctors are not really sure, but smoking does seem to be one
of several factors that work together to promote the formation of ulcers.
For example, some research suggests that smoking might increase a person's
risk of infection with the bacterium Helicobacter pylori (H. pylori).
Most peptic ulcers are caused by this bacterium.
Stomach acid is also important in producing ulcers. Normally, most of this
acid is buffered by the food we eat. Most of the unbuffered acid that enters the
duodenum is quickly neutralized by sodium bicarbonate, a naturally occurring
alkali produced by the pancreas. Some studies show that smoking reduces the
bicarbonate produced by the pancreas, interfering with the neutralization of
acid in the duodenum. Other studies suggest that chronic cigarette smoking may
increase the amount of acid secreted by the stomach.
Whatever causes the link between smoking and ulcers, two points have been
repeatedly demonstrated: People who smoke are more likely to develop an ulcer,
especially a duodenal ulcer, and ulcers in smokers are less likely to heal
quickly in response to otherwise effective treatment. This research tracing the
relationship between smoking and ulcers strongly suggests that a person with an
ulcer should stop smoking.
Liver disease
The liver is an important organ that has many tasks. Among other things, the
liver is responsible for processing drugs, alcohol, and other toxins to remove
them from the body. There is evidence that smoking alters the ability of the
liver to handle such substances. In some cases, this may influence the dose of
medication necessary to treat an illness. Some research also suggests that
smoking can aggravate the course of liver disease caused by excessive alcohol
intake.
Crohn's disease
Crohn's disease causes inflammation deep in the lining of the intestine. The
disease, which causes pain and diarrhea, usually affects the small intestine,
but it can occur anywhere in the digestive tract. Research shows that current
and former smokers have a higher risk of developing Crohn's disease than
nonsmokers do. Among people with the disease, smoking is associated with a
higher rate of relapse, repeat surgery, and immunosuppressive treatment. In all
areas, the risk for women, whether current or former smokers, is slightly higher
than for men. Why smoking increases the risk of Crohn's disease is unknown, but
some theories suggest that smoking might lower the intestine's defenses,
decrease blood flow to the intestines, or cause immune system changes that
result in inflammation.
Gallstones
Several studies suggest that smoking may increase the risk of developing
gallstones and that the risk may be higher for women. However, research results
on this topic are not consistent, and more study is needed.
Can the damage be reversed?
Some of the effects of smoking on the digestive system appear to be of short
duration. For example, the effect of smoking on bicarbonate production by the
pancreas does not appear to last. Within a half-hour after smoking, the
production of bicarbonate returns to normal. The effects of smoking on how the
liver handles drugs also disappear when a person stops smoking. However, people
who no longer smoke still remain at risk for Crohn's disease. Clearly, this
question needs more study.
For more information
Information about smoking and health is available from
Office on Smoking and Health
National Center for Chronic Disease Prevention and Health Promotion
Mail Stop K-50
4770 Buford Highway NE.
Atlanta, GA 30341-3717
Phone: 1-800-CDC-1311 (232-1311)
Fax: 1-888-CDC-FAXX (888-232-3299)
Email: tobaccoinfo@cdc.gov
Internet: http://www.cdc.gov/tobacco/
Source: National Institutes of Health; National Institute of Diabetes
and Digestive and Kidney Diseases
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