Skip to content

Study after study is suggesting that exposure to lots of diverse bacteria and microorganisms (think farms with animals) is healthy for the developing immune system. From Science Daily:

Growing up on livestock farm halves risk of inflammatory bowel diseases

New research conducted at Aarhus University has revealed that people who have grown up on a farm with livestock are only half as likely as their urban counterparts to develop the most common inflammatory bowel diseases: ulcerative colitis and Crohn's disease

"It is extremely exciting that we can now see that not only allergic diseases, but also more classic inflammatory diseases appear to depend on the environment we are exposed to early in our lives," relates Vivi Schlünssen, Associate Professor in Public Health at Aarhus University.

"We know that development of the immune system is finalized in the first years of our lives, and we suspect that environmental influences may have a crucial effect on this development. The place where you grow up may therefore influence your risk of developing an inflammatory bowel disease later in life."

However, the researchers have a theory that the body may be dependent on exposure to a wide variety of microorganisms to develop a healthy immune system -- in the same way as has been established in studies on allergies and asthma.

"We know that the difference in the microbial environment between city and country has increased over the past century, and that we are exposed to far fewer different bacteria in urban environments today than we were previously. This may in part explain our findings," says Signe Timm.

Over the past 40-50 years, incidence of the diseases has sky-rocketed in Northern Europe -- including Denmark -- as well as in Canada and the United States, although they are still relatively rare in developing countries.

Another article reporting on the Crohn's disease study I posted yesterday. But this article lists the depleted bacteria and also which ones there are too much of in Crohn's patients. It illustrates that gut microbial communities being out of whack go hand in hand with disease. Remember: dysbiosis means an imbalance in the microbial populations. Interestingly, just like in the 2012 sinusitis study (see my December 4, 2013 post) - it's biopsies that found the specific bacterial imbalances, and not fecal samples or mucus/phlegm swabs (typically done in sinusitis). Big step forward in human microbiome research. And again antibiotics are not the answer.

From Science magazine:

Crohn's Disease Marked by Dramatic Changes in Gut Bacteria

The largest clinical study of its kind is revealing new insights into the causes of Crohn's disease, a periodic inflammation of the intestines. The research, which involved 668 children, shows that numbers of some beneficial bacteria in the gut decrease in Crohn's patients, while the number of potentially harmful bacteria increases. The study could lead to new, less invasive diagnostic tests; it also shows that antibiotics—which aren't recommended for Crohn's but are often given when patients first present with symptoms—may actually make the disease worse.

Crohn’s disease is one of the two major inflammatory bowel diseases (IBDs); the other is ulcerative colitis, a similar condition that affects only the colon. Both have been on the rise in the developing world since the early 1950s; now, an estimated 1.4 million people suffer from IBD in the United States alone. Symptoms include diarrhea, abdominal pains and cramping, and intestinal ulcers.

But genes alone can't explain the sharp rise in IBD incidence, and scientists have looked at the environment—in particular diet and antibiotic use—for answers.

Several studies have shown that Crohn’s disease is characterized by microbial dysbiosis, a shift in the microbial populations inhabiting the gut, but it's difficult to unravel cause and effect: A change in gut microbiota can cause inflammation, but the reverse can also occur. Complicating the picture is the fact that before being diagnosed with IBD, patients often receive antibiotics to fend off a supposed gut infection that could be causing the symptoms, which also have a powerful impact on the microbial populations living in our guts.

Now, a group headed by Ramnik Xavier, a gastroenterologist at Harvard Medical School in Boston, has collected fecal samples and taken biopsies of the lower part of the small intestine and rectum from 447 children who had just been diagnosed with Crohn's, and a control group of 221 kids who had noninflammatory abdominal symptoms, such as bloating and diarrhea. In contrast with previous studies, the majority of patients had not yet received antibiotics or anti-inflammatory drugs. Based on their genetic material, the researchers determined the relative abundance of a range of microbial species in the samples.

Some potentially harmful microbial species were more abundant in Crohn's patients, such as those belonging to the Enterobacteriaceae, Pasteurellaceae, Veillonellaceae, and Fusobacteriaceae; numbers of the ErysipelotrichalesBacteroidales, and Clostridiales, generally considered to be beneficial, were lower. The disappearance and appearance of species can be equally important, says Dirk Gevers of the Broad Institute in Cambridge, Massachusetts, who performed most of the work. "There has been a shift in the ecosystem, which affects both types.”

But those differences were found mostly in the biopsy samples; there weren't many differences between the feces from Crohn's patients and the control group. At this early stage of the disease, "the dysbiosis seems not to have reached the stool yet," Gevers says.

The dysbiosis was also more pronounced in patients who had received antibiotics. "This study confirms that these drugs don’t do any good to people with Crohn’s disease," says gastroenterologist Séverine Vermeire of the Catholic University of Leuven in Belgium, who was not involved in the study. "We knew antibiotic use increases the risk to develop the disease; now we know they can worsen it, too."

Vermeire says it's a "missed opportunity" that the researchers didn't look at the patients' diets. "That could have helped elucidate why this disease occurs so much more in the Western world than elsewhere." In 2011, Vermeire’s group published a study showing that healthy family members of Crohn's disease patients have a slight dysbiosis as well. Vermeire is convinced that even in these families, it's not genetics but some lifestyle factor that causes the phenomenon. "If we could identify the dysbiosis in an early stage, and we knew the causative factors,” she says, “we could prevent disease occurrence by bringing about lifestyle changes.”