Children who grow up in the company of canines may be less likely to develop Crohn’s disease later in life, according to a new study that gives dogs a healthy leg up in the battle of household pets.
The research, presented during Digestive Disease Week in San Francisco, found that having a dog — particularly between the ages of five and 15 — appeared to offer protection against inflammatory bowel disease (IBD) by promoting healthy gut permeability and a balance between microbes in the gut and the body’s immune response. This protective effect, which was not observed with cats, was also seen in infants who lived with three or more family members during the first year of life.
“Our study seems to add to others that have explored the ‘hygiene hypothesis’ which suggests that the lack of exposure to microbes early in life may lead to lack of immune regulation toward environmental microbes,” said Williams Turpin, the study’s senior author and a research associate at Mount Sinai Hospital and the University of Toronto.
Canada has one of the highest rates of inflammatory diseases in the world, according to Crohn’s and Colitis Canada, with around 300,000 people currently living with IBD. Crohn’s disease and ulcerative colitis, the two main forms of IBD, are diseases that cause inflammation in the lining of the gastrointestinal tract and interfere with the body’s ability to digest food, absorb nutrients and efficiently remove waste. The rate of Crohn’s and colitis among Canadian children has increased by more than 50 per cent over the past 10 years, with symptoms of these chronic diseases, which can recede and return over time, including abdominal pain, severe diarrhea, rectal bleeding and weight loss.
To gain a better understanding of the environmental factors that may affect the disease, researchers administered an environmental questionnaire to nearly 4,300 first-degree relatives of patients with Crohn’s disease who were enrolled in the Crohn’s and Colitis Canada Genetic, Environmental and Microbial (CCC-GEM) project. Using this information, combined with historical data acquired at the time of recruitment, they were able to analyze multiple factors, including family size, the presence of dogs or cats, living on a farm, the number of bathrooms in the home and drinking unpasteurized milk and well water.
They found that early exposure to dogs was associated with factors that result in a healthy gut microbiome, which is believed to offer protection against many health conditions, including IBD, diabetes, colorectal cancer and hypertension. The effects were seen across all age groups but particularly between the ages of five and 15, though the team was unable to determine exactly why dog ownership or living with a larger family offered this protection.
“We did not see the same results with cats, though we are still trying to determine why,” Turpin said. “It could potentially be because dog owners get outside more often with their pets or live in areas with more green space, which has been shown previously to protect against Crohn’s.”
The team hopes the findings may help physicians ask the kind of detailed questions that help determine which patients face the greatest risk of Crohn’s disease and other health conditions linked to the gut microbiome. The study was limited by its reliance on questionnaires — which are subject to recall bias — in determining the presence of early life environmental factors.
Dave Yasvinski is a writer with Healthing.ca