Growing up with a dog is healthier for your gut: Toronto study

Researchers from Sinai Health and the University of Toronto have found that growing up with a dog is associated with a decreased risk of developing Crohn's disease.

Their research shines new light on how environmental factors influence the onset of this inflammatory bowel condition and could inform future prevention strategies.

The research was led by Kenneth Croitoru, a clinician-scientist at the Lunenfeld-Tanenbaum Research Institute (LTRI), part of Sinai Health, and Williams Turpin, a research scientist at Sinai Health. Croitoru and Turpin are also part of Mount Sinai Hospital’s Centre for Inflammatory Bowel Disease (IBD), one of the largest centres globally dedicated to researching and treating IBD.

The team investigated how dozens of environmental factors impact the likelihood of developing Crohn’s as part of their overarching effort to be able to predict those at risk and potentially intervene early.

“The idea behind predicting someone's risk of disease is that you can then also begin to understand who you might want to do something to try and prevent disease,” says Croitoru, who holds the Canada Research Chair in Inflammatory Bowel Diseases and is a professor of medicine and immunology at U of T’s Temerty Faculty of Medicine.

Their study, published in Clinical Gastroenterology and Hepatology, found that early exposure to dogs correlates with beneficial changes in gut bacteria, gut permeability and blood biomarkers.

Conversely, people who lived with a bird at the time of study were more likely to get Crohn’s.

“We don’t know why living with a dog makes someone less prone to Crohn’s disease, but this is what our data shows,” says Croitoru, who is also a gastroenterologist at Mount Sinai Hospital.

“We have established associations between environmental factors and Crohn’s and are now trying to understand how these environmental factors affect the triggering of the disease.”

Caused by inflammation in the gastrointestinal tract, Crohn’s disease can have far-reaching consequences on overall health and well-being. Its incidence among children under 10 has doubled since 1995, while the annual cost of IBD to Canada is estimated at $5.4 billion per year, according to Crohn’s and Colitis Canada, a non-profit dedicated to finding cures for the most common types of inflammatory bowel disease.

The likelihood of getting Crohn’s is strongly influenced by genetics, but the environment also plays a role. While we can’t change our genes, we can modify our surroundings and diet, for example, to potentially prevent the disease from occurring, says Croitoru.

These findings come from the Genetic, Environmental and Microbial (GEM) Project, the largest study of its kind that seeks to identify potential triggers of Crohn’s disease. Coordinated at Mount Sinai Hospital since 2008, the GEM Project has been collecting comprehensive medical and lifestyle data from over 5,000 healthy first-degree relatives of people who have Crohn’s and come from all over the world, including Australia, Canada, Israel, New Zealand, U.K. and the U.S.

In the 15 years since the study began, over 120 people have developed the disease.

“By understanding what is different about those who develop the disease, we should be able to predict who is at risk,” says Croitoru.

Previously, the group identified differences in the microbiome and other biomarkers in people who go on to develop Crohn’s and those who don’t. In another recent report published in Gastroenterology, Sun-Ho Lee, a clinician-scientist at Mount Sinai Hospital’s IBD Centre and an assistant professor at the Institute of Medical Science at Temerty Medicine, used the available data and machine learning to develop an“integrative risk score” that predicts the risk of Crohn’s with a high degree of accuracy.

But risk prediction is only the first step, says Croitoru, whose ultimate goal is to be able to intervene and prevent the disease from starting. He and his team are now doing research that seeks to devise and test strategies for prevention by, for example, adding supplements to the diet to promote a healthy microbiome.

“Sinai Health is committed to groundbreaking research and bringing those discoveries to patients. By integrating genetic, environmental, and microbial data, Dr. Croitoru and colleagues are paving the way towards personalized intervention strategies that could significantly reduce the incidence of Crohn’s disease," said Anne-Claude Gingras, director of LTRI and vice-president of research for Sinai Health.

The GEM Project has been funded by the Crohn’s and Colitis Canada, the Canadian Institutes of Health Research and the Helmsley Charitable Foundation.