Dog lovers can attest to the range of benefits that come with having a canine companion, but improved gut health likely isn't one of them.
That may be about to change following research from Sinai Health and the University of Toronto that shows exposure to dogs during childhood is linked to beneficial changes in gut bacteria, gut permeability and blood biomarkers.
The study, published in Clinical Gastroenterology and Hepatology, found living with a dog between ages five and 15 is associated with a healthier gut microbiome and reduced risk of developing Crohn's disease.
The research shines new light on how environmental factors influence the onset of Crohn's - an inflammatory bowel condition - and could inform future prevention strategies.
For the study, researchers led by Kenneth Croitoru and Williams Turpin of Mount Sinai Hospital's Centre for Inflammatory Bowel Disease (IBD) 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, a clinician-scientist at the Lunenfeld-Tanenbaum Research Institute (LTRI), part of Sinai Health, and a professor of medicine and immunology at U of T's Temerty Faculty of Medicine.
Croitoru notes the study doesn't reveal why living with a dog makes someone less prone to Crohn's disease. "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," says Croitoru, who is also a gastroenterologist at Mount Sinai Hospital.
The study also found living with a large-sized family in the first year of life to reduce the likelihood of getting Crohn's. It also found people who lived with a bird at the time of study were more likely to develop 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 inflammatory bowel disease to Canada is estimated at $5.4 billion per year, according to Crohn's and Colitis Canada, a national non-profit.
The likelihood of getting Crohn's is strongly influenced by genetics, but the environment also plays a role, says Croitoru, who holds the Canada Research Chair in Inflammatory Bowel Diseases. While we can't change our genes, we can modify our surroundings and diet, for example, to potentially prevent the disease from occurring.
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, the U.K. and the U.S.
The project is funded by Crohn's and Colitis Canada, the Canadian Institutes of Health Research and the Helmsley Charitable Foundation.
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 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 conducting 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," said Anne-Claude Gingras, director of LTRI and vice-president of research at Sinai Health.
"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."
