Ulcerative Colitis and Smoking: 10 Things You Need to Know

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Learning about ulcerative colitis (UC) can be downright confusing. One of the most complex areas of UC research relates to the relationship between UC and smoking. While some research actually shows that smoking has a positive effect on UC, the story is not that straightforward. Read ahead to find out what we do and don't know about smoking and UC.


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Causes of UC are not completely understood

When it comes to smoking’s impact on UC, it is important to understand that inflammatory bowel disease (IBD) involves a complex interplay between different factors, including your genetics, immune system and gut bacteria. Each of these systems involves a complicated network of cells and are unique to you.


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Environmental factors play a role

Genetics only account for a fraction of your UC risk. This means that environmental factors also play a role in your disease. Studies have suggested that environmental factors also matter, including urban environment, the oral contraceptive pill, appendectomy, and tobacco smoking.


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Smoking appears protective

In multiple studies, UC is less common in smokers than in non-smokers. And, in those who already have UC, those who smoke have less severe symptoms. Despite the clear relationship between smoking and UC, the reasons for this relationship are still not understood. Both cigarette smoke and UC are highly complex.


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Smokers are less likely to receive a colectomy

A colectomy is a surgical procedure to remove all or part of a colon. In a 10-year study, researchers found a reduction of colectomy rates in the smokers with UC compared to the non-smokers with UC. In those that smoked, there was a 32 percent rate of colectomy and the non-smokers had a 42 percent rate.


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Secondhand smoke may increase risk of IBD in children

Exposure to cigarette smoke seems to increase the risk of both Crohn’s disease and UC in children. Children who are exposed to maternal smoking at birth and also smoking by others are at an increased risk of developing IBD.


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Smoking impacts men and women’s UC risk differently

While smoking has been reported to be protective against UC, it does not seem to be as protective for women as for men. In one study where the male smokers were compared with non-smokers, the age of UC onset was significantly increased in the male smokers (41 years old) versus the non-smokers (32 years old). This age difference was not seen in the women smokers versus the non-smokers (33 years in both groups).


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Racial differences need to be explored

Many of the studies related to smoking and UC have been done only with Caucasian study participants. However, in the United States, American Indians, Alaska Natives, and African Americans have the highest adult smoking rates, according to the American Lung Association.


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Smoking impacts fertility

Even if smoking protects against UC in men, smoking also impairs fertilization capacity. The tobacco combustion produces many chemical compounds with potential detrimental effects on male germ cells. Stopping smoking is known to have a positive effect on male fertility.


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Bottom line: Smoking is a risk factor for many other diseases

James Lindsay, Ph.D., a gastroenterologist and professor of inflammatory bowel disease at the London School of Medicine, summed it up in an email interview with HealthCentral: “There is clear evidence that smoking cigarettes reduces disease severity in those with UC. However, the negative impact of smoking on increasing risk of heart disease and stroke far outweighs this potential benefit on UC. We advise all our patients to quit smoking.


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Smoking research could lead to future UC treatments

The research on smoking and UC may offer a potential for treatment. However, according to Dr. Lindsay, we are not there yet. “It is still not clear exactly which components of tobacco smoke result in its beneficial effect. Recent research has highlighted the role of the aryl hydrocarbon receptor as one means by which the environment acts on the gut immune system. Current studies are assessing whether targeting this receptor has benefit in patients with UC.”