By Michael Chiorean, MD **
There are more than 1 million people affected with inflammatory bowel disease (IBD) in the United States — about equally distributed between ulcerative colitis and Crohn’s disease. However, the IBD “map” has changed substantially in the last half century throughout the world. Virtually every recent study showed the frequency of these poorly understood disorders has increased, in some cases more than fivefold since the 1950s. And while there is still a fairly strong East-West gradient, developing countries such as India, China and South Korea, where IBD was almost unheard of 30 years ago, have seen a dramatic acceleration of new cases (incidence) that is now paralleling the incidence in the Western world. In fact, it is expected if the current trend continues, most new cases, and the highest disease burden in the world, will be in countries from the Eastern Hemisphere.
This phenomenon has puzzled scientists who have studied these disorders for a long time and, so far, an explanation has remained elusive. Most scientists believe IBD is the result of the interplay between the environment, diet, certain medications, genetic variables and an overreactive immune response against normal bacteria in the gut. If all these “planets” align the right way, an individual who may have a genetic predisposition will develop IBD.
Alternative TheoriesScientists were not the only ones who tried to provide answers to this enigma. Several unfounded theories have gained some popularity in the general public, in large part by means of social media, and for perhaps no other reason than the fact that they are more fanciful and sometimes sensational in comparison to scientific concepts. Such theories include the intoxication theory (aluminum, artificial sweeteners, food dyes and preservatives are among the most favorite culprits) or even some religious or spiritual theories. For instance, King Alfred of England suffered from an ailment causing pain and “embarrassment” after eating, beginning in his early 20s. He carried his suffering for most of his life. At the time, this was thought to be due to witchcraft, as a punishment for the king’s notorious infidelity. In reality, he was probably suffering from Crohn’s disease.
The Hygiene Hypothesis
The “hygiene hypothesis” suggests our hypersanitary lifestyle is what predisposes genetically prone individuals to develop IBD or other autoimmune or allergic disorders, such as diabetes, rheumatoid arthritis, lupus and asthma. Countries with a higher frequency of infections and parasites have a lower frequency of IBD and vice versa.
In one study from Africa, offspring of women treated for parasites during pregnancy had twice the rate of asthma and allergic disorders compared to children from women who were not treated. Some parasites have developed ways to tame the immune system in the gut in such a way as to become stealthy and induce what we call immune tolerance. Thus, they are able to maintain a relatively peaceful residence in the intestine, where they feed by “stealing” some of the available nutrients. Since we likely coexisted with parasites for millennia, it is possible that people with stronger gut immune systems were able to get rid of parasites faster, gaining a nutritional advantage over their peers when food was scarce and malnutrition was rampant. As intestinal parasites have almost disappeared from most developed countries, the immune system in some individuals may be looking for an alternative target and may find an acceptable “sparring partner” in the normal bowel flora, resulting in progressive inflammation. Normal people are “tolerant” to intestinal microbiota, while subjects with IBD may lose such tolerance and become immunologically overreactive. The bowel may well be an innocent bystander in this process, but it suffers substantial collateral damage resulting in what is usually a self-perpetuating, chronic disease. IBD patients who were administered a species of relatively harmless parasites (pig whipworm) in a few clinical studies, had improvement in their IBD activity, at least short term.
The seemingly endless supply of sanitary and cleansing products, which eliminate 99.99 percent of bacteria and help rid us of serious foodborne illnesses, have probably altered the nature and diversity of friendly bacteria that have colonized our collective bowels for thousands of years. These friendly bacteria were our first line of defense against noxious organisms at a time when antibiotics and vaccines were not available. Consequently, our gain in some infectious diseases may translate in a loss as far as autoimmune disorders.
- “Early Life Immunological Education”
While the hygiene hypothesis has not been proven beyond reasonable doubt, it helps explain certain IBD features. For instance, IBD tends to be less common among children with multiple siblings or those who attended day care and undoubtedly share extensive “bug repertoires” with their peers in childhood. (As a side, IBD seems to be also less frequent in children born through vaginal delivery and are breast-fed.) In contrast, IBD is more frequent among children who received multiple antibiotics. While this is by no means cause and effect, the association is at least interesting, if not mesmerizing. This suggests the immune “education” that occurs early in life through exposure to a variety of bugs has long-lasting consequences for a healthy and balanced immune system. So the old adage of letting your children “eat dirt” may have a seed of truth in it and a very important one in IBD.
It is worth mentioning here that vaccines have not been associated with IBD. In fact, they have a very important role in protecting all individuals, including those with IBD and particularly those who are on immunosuppressive drugs against serious infections.
Michael Chiorean, MD, is a gastroenterologist with the Digestive Disease Institute at Virginia Mason. He specializes in inflammatory bowel disease, Crohn’s disease, ulcerative colitis, C Difficile, gastrointestinal bleeding and small bowel endoscopy.