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What causes IBD?
Inflammatory bowel diseases, which include Crohn’s disease and ulcerative colitis, are a bit mysterious. Both chronic and serious, these conditions are triggered by an abnormal immune reaction that can lead to diarrhea, abdominal cramps, rectal bleeding, fever, joint pain, loss of appetite, and fatigue, not to mention fistulas and serious complications that can require surgery to remove the colon.
Research has given us some hints as to the causes of IBD. It has been found that a combination of genes and environmental exposures is probably to blame. Here are some factors that may affect IBD risk.
Where you live
People who live in Western countries like the United States and Europe have a higher IBD risk than those in other parts of the world. The reason could be lifestyle factors such as smoking, diet, or pollution.
But Latin America, Japan, Southeast Asia, and India have had an explosion in cases in the last two decades.
We could be "poisoning the world with our McDonalds’ and fatty fried foods," says Balfour Sartor, MD, chief medical advisor for the Crohn’s & Colitis Foundation of America. "We’re purifying water, embarking on sanitation, and dramatically changing the environment. Any one or a combination of these factors could be affecting this."
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Although there is a spike in new IBD cases in people ages 50 to 60, most patients are diagnosed as adolescents or young adults.
And pediatricians believe there is a decrease in age of onset, says Dr. Sartor. About 15% of IBD patients develop it before age 18.
"There is pretty good evidence that the younger you are when you develop the disease, the more aggressive its course," he says. "It’s also thought that if you develop the disease early in life, there is a stronger genetic basis, whereas later in life, it is probably more of an environmental basis."
There’s no question that smoking can devastate health. Still, for some reason, smokers are at lower risk of developing ulcerative colitis.
The opposite is true for Crohn’s disease: It is more common among smokers, and smoking can also make symptoms worse in these patients, says Dahlia Awais, MD, a gastroenterologist at University Hospitals Case Medical Center in Cleveland.
Prescribing a nicotine patch for some UC patientstypically smokers who have kicked the habitisn’t uncommon, as it can ease symptoms during an outbreak.
People (usually those under 20) who’ve had their appendix removed because of appendicitis are at lower risk of ulcerative colitis and have milder cases of the disease. The catch? The surgery seems to be beneficial only if it is done before the condition is diagnosed, and people with active UC probably don’t benefit from an appendectomy.
Research suggests that an appendectomy also delays the onset of Crohn’s disease.
Dr. Awais says the connection could be the immune system. An appendectomy may result in an altered immune response that provides protection against UC, she explains.
"Family history certainly increases risk," Dr. Awais says. "But IBD is not just one factor.… It’s much more complicated than that."
About 30 genes have been associated with UC and 71 genetic differences with Crohn’s disease. However, experts believe the environment is the initial trigger for both diseases.
"The combination of genetics and environment is entirely true," Dr. Sartor says, because in identical twins, if one has Crohn’s, there’s only a 50% likelihood the other will develop the disease. For UC, it’s only 6%.
One theory is that exposure to intestinal parasites may lower IBD risk. The thinking is that the human immune system evolved over millions of years to cope with the invaders, but people in developed nations rarely come into contact with the worms because of better living conditions, says Dr. Sartor.
This may set the stage for an abnormal immune reaction that causes IBD. However, this theory remains unproven.
That said, some experts are studying whether treating IBD patients with intestinal parasites may help curb symptoms.
Environmental exposures that affect the risk of IBD may include medication.
For example, some research has linked long-term oral contraceptive use to a higher risk of both UC and Crohn’s disease, and long-term hormone replacement therapy to a higher risk for Crohn’s.
Other drugs, such as the acne drug isotretinoin (Accutane), could play a role. And pain-relieving NSAIDs (like ibuprofen) can worsen IBD symptoms but are not thought to increase the risk of getting the disease in the first place.
There’s conflicting research as to whether specific eating habits are associated with a greater risk of IBD.
One Japanese study reported an increased risk of Crohn’s disease for women who consume a lot of proteinparticularly from animal products. Other studies have reported a possible link to high-fat and high-sugar diets.
IBD is more common in whites of northern European decent and in the Ashkenazi Jewish population. Why? It could be that these groups are more likely to have genes associated with IBD as well as live in industrialized areas. However, the ethnicity gap seems to be narrowing.
IBD symptoms may also differ among various racial groups, though this is an area that needs more research, Dr. Awais says.
Some studies suggest that African Americans are more likely than white people to need surgery because of IBD.
Bacteria in the colon
The gastrointestinal tract contains trillions of bacteria that help digest your food. These are "good" germs.
However, infections with "bad" germs, such as salmonella and campylobacter, have been associated with a greater risk of IBD.
Both types of bacteria can be ingested through contaminated food, and they are responsible for thousands of cases of food poisoning each year.