What Causes Celiac Disease?
Your genes are important, but so are other factors
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It's not entirely clear what causes celiac disease. In fact, most researchers believe multiple factors are involved, all of which may be necessary for the condition to develop.
Your genes play a strong role—if you don't have one of the two specific genes that have been linked to celiac disease, your odds of developing the condition are very low (although not zero). However, a large minority of the population (some 40%) actually carries one or both of those genes, so genetics isn't the only factor in play here.
To develop celiac disease, you must be eating gluten. When you have celiac disease, gluten spurs your immune system to damage your small intestine. Still, gluten is extremely common in Western-style diets (most people eat gluten—and frequently lots of it—several times each day), and still only about 1% of people develop celiac disease.
Finally, for you to develop celiac disease, factors in your environment must help to cause it. It's these "factors" that aren't clear; some people can consume gluten every day for decades without a problem and then develop severe celiac disease symptomsvery suddenly, while some young children exhibit celiac symptoms as soon as gluten-containing grains are introduced into their diets.
One study suggests that a common virus may, in some people, contribute to the development of celiac disease. However, the study is preliminary and more research is needed to tease out the true effects.
"Trigger" May Help to Cause Celiac Disease
Some researchers have hypothesized that celiac disease requires a "trigger," which may possibly take the form of a health issue or even major emotional stress; for example, many women begin to experience celiac symptoms following pregnancyand birth, and other people find their symptoms begin following a seemingly unrelated illness, or even following a stressful time in their life.
However, this "trigger" theory remains unproven.
Other scientists think the gluten content in our diets—which has grown considerably over the past 40 years, both as we eat more grain products and as wheat itself is bred to contain higher gluten levels—could be responsible for causing more cases of celiac disease. There's some circumstantial evidence for this theory, since one recent study found that the incidence of celiac disease has doubled every 15 years since 1974.
Still others are focusing on celiac disease at the molecular level. A recent study fingered two chemical signals—interleukin 15 and retinoic acid, a derivative of vitamin A—as potential initiators of the body's inflammatory response to gluten. The researchers looked at people with diagnosed celiac disease, and found they had high levels of interleukin 15 in their intestines. When they induced high levels of that same chemical in mice, the mice developed early signs of celiac disease. Retinoic acid worsened the symptoms and the damage.
When the researchers blocked the interleukin 15, however, the mice reverted to normal and were able to tolerate gluten again. This led the scientists to speculate that high levels of interleukin 15 in your intestines might cause celiac disease.
(Of course, it's still not clear what might cause higher levels of interleukin 15 to develop in your intestines.) Still, if that's the case, medications that block interleukin 15 (which already are in trials in rheumatoid arthritis patients) might also help to treat celiac disease.
Possible Link Between Celiac and Reovirus?
Scientists have identified a potential link between celiac disease and a type of virus called a reovirus. Reovirus infects many people, usually when they are infants, but causes few or no symptoms. The study, published in the journal Science, used mice that were specially bred to be more susceptible to celiac disease.
The researchers found strong immune system responses in those mice when they were infected with the virus and then fed gluten.
The researchers also analyzed people already diagnosed with celiac disease, looking specifically for antibodies to this particular virus. They found much higher levels of reovirus antibodies in people with celiac—two to five times higher than in people without the condition.
This study doesn't come close to proving reoviruses cause—or even trigger—celiac disease. Researchers will need to conduct additional studies to see if the link holds up. However, if reoviruses do turn out to contribute to the development of celiac disease, it's possible that a vaccine could help protect people who have the genes.
Cause of Celiac Disease Still Not Clear, Despite Research
So to sum up, celiac disease is caused by: having the right genes, eating gluten, and possibly by some sort of trigger.
One theory that's not correct is the popular one blaming the rise in celiac disease and non-celiac gluten sensitivity on genetically modified wheat. Since genetically-modified wheat isn't on the market anywhere, it can't be causing an increase.
However, medical science still doesn't know much about any potential triggers, even though those seem to be the key to why some people with the "right" genes develop celiac disease while others do not. In fact, researchers have only begun to explore the various possibilities. It's likely, too, that there are other genes involved that haven't yet been identified.
There's no doubt, though, that determining a cause for celiac disease might help to hasten development of a pharmaceutical-based treatment. Alessio Fasano, MD, director of both the University of Maryland's Mucosal Biology Research Center and Center for Celiac Research, says research into possible environmental triggers for celiac disease is very important—identifying causes of celiac disease may help to create celiac disease treatments or even to prevent the condition entirely.
Sources:
Bouziat R et al. Reovirus Infection Triggers Inflammatory Responses to Dietary Antigens and Development of Celiac Disease. Science. 2017 Apr 7;356(6333):44-50.
Catassi C. et al. Natural history of celiac disease autoimmunity in a USA cohort followed since 1974. Annals of Medicine. October 2010, p. 530-8.
University of Chicago Celiac Disease Center. Symptoms.
University of Chicago News. Human and mouse studies sharpen focus on cause of celiac disease.
University of Maryland School of Medicine News. University of Maryland Center for Celiac Research Finds Rate of Celiac Disease is Growing.
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