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Farms Shield Kids From Bowel Disease

Barnyard dirt may bolster young immune systems, research suggests

MONDAY, Aug. 6, 2007 (HealthDay News) -- Children regularly exposed to farm life as babies are about half as likely as other kids to develop inflammatory bowel diseases such as ulcerative colitis or Crohn's disease, German researchers report.

The findings, published in the August issue of Pediatrics, fall into line with what experts in inflammatory bowel diseases (IBDs), allergy and asthma call the "hygiene hypothesis."

That theory "refers to the observation that children living in environments with lower levels of microbial exposure seem to be at higher risk for the development of allergies," explained the study's lead researcher, Katja Radon, of Ludwig-Maximilians-University in Munich.

Crohn's and ulcerative colitis are autoimmune illnesses, where the body's immune system mistakenly attacks its own tissues. It is possible that this dysfunction may originate, at least in part, in how immune responses develop very early in life, said Dr. Joel Rosh, director of pediatric gastroenterology at Goryeb Children's Hospital, part of the Atlantic Health System in Morristown, N.J.

He pointed out that while rates of IBDs are holding steady in the developing world, they are rising sharply in more affluent nations.

"It's something that we are doing to ourselves," Rosh said.

"The thinking is that if your immune system isn't appropriately challenged at the appropriate time in life, then it might do some wacky things," Rosh added. In other words, a too-clean environment -- while healthy in some ways -- might be less than ideal when it comes to immune-linked illness, experts say.

The German study is one of the first to compare inflammatory bowel disease rates against infant exposures to farm animals and farm life. The German team questioned the parents of more than 2,200 6- to-18-year-old children. More than 300 of the children had ulcerative colitis, another 444 had Crohn's, and almost 1,500 were free of either illness.

Kids with either Crohn's or ulcerative colitis "were less likely to have lived in rural environments and were less likely to have farm contact in the first year of life, before the disease had developed," Radon noted.

In contrast, children who had spent regular amounts of time visiting or living on farms during their first year of life were 50 percent less likely to develop Crohn's as they got older and 60 percent less prone to ulcerative colitis, compared to youngsters who had not had that experience.

Early exposure to cattle, especially, appeared to help keep the diseases at bay, cutting the odds of Crohn's by 60 percent and colitis by 70 percent, the study authors said.

Cattle appeared to have a more potent effect on IBD risk than exposure to household pets, the study found. Household cat and dog exposure has been the focus of much study and debate among allergists and immunologists.

In this study, regular exposure in infancy to cats reduced Crohn's risk by just 20 percent, a statistic the researchers described as only of "borderline significance." Cat exposure was somewhat more useful against colitis, with rates dropping by 50 percent compared to unexposed children.

The cat-cattle discrepancy didn't come as a big surprise to Rosh.

"It seems that it's not so much animals, per se, as it is which animals," he said. "So, the domesticated cat that stays in the corner cleaning himself all day may not be 'dirty enough' to save you."

Radon agreed. "It has also been shown for allergies that farm animal contact is more efficient [in reducing risk] than pet contact. Therefore, it is not surprising that we see the same for inflammatory bowel disease," she said. "The reason might be that the level of exposure to bacteria and fungi in the farm environment is much higher than if you have a cat or dog at home."

Rosh has his own theories as to where the protective element might lie. "They sanitize it in the article, but they do say it can't be a clean animal -- it's got to be livestock. It's got to be something in that environment, and I would say, it's not in the air so much, as in the poop," he said.

So, does all this mean that modern-day babies need to get "back to the land"?

Perhaps not, according to the experts.

"You can't make the leap to say that to protect our children against autoimmune disease, we need to take them to farms, because we don't know yet what the [protective] exposure is," said Dr. Peter Mannon, head of the Clinical Inflammatory Bowel Diseases Research Unit at the U.S. National Institute of Allergy and Infectious Diseases.

"Are you supposed to be exposed to hay? To a particular type of vermin? The rats in barns? It's very hard to know," he said. While there's no reason not to bring infants to more pastoral settings, "I would not guarantee that it is going to add any protection," Mannon said.

Radon agreed that "at the moment, we cannot give direct advice to parents" since the study showed no cause-and-effect relationship, only an association.

And she pointed out that society's obsession with cleanliness does have its rewards. "We should not forget that an improved level of hygiene has relevantly contributed to today's health in industrialized countries," she said.

For his part, Rosh said there might be some virtue in letting kids get a little dirty -- a prescription most youngsters should have no problem with.

"I don't mean that we all have to eat dirt, but if we could isolate what is in it that is good, maybe we'd have a good [IBD] treatment," he said. "These various areas of research are going to unlock the secrets that we need to cure these diseases."

More information

There's more on the hygiene hypothesis at the American Academy of Allergy, Asthma & Immunology.

SOURCES: Katja Radon, Ph.D., head, Unit for Occupational and Environmental Epidemiology, Ludwig-Maximilians-University, Munich, Germany; Joel Rosh, M.D., director, pediatric gastroenterology, Goryeb Children's Hospital, Atlantic Health System, Morristown, N.J.; Peter Mannon, M.D., head, Clinical Inflammatory Bowel Diseases Research Unit, U.S. National Institute of Allergy and Infectious Diseases, Bethesda, Md.; August 2007, Pediatrics
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