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:
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.