Thesis Defence: A Journey from India to Canada—The Westernization of the Gut Microbiome is Associated with Dietary Acculturation in Indian Migrants

Leah D’Aloisio, supervised by Dr. Deanna Gibson, will defend their thesis titled “A Journey from India to Canada: The Westernization of the Gut Microbiome is Associated with Dietary Acculturation in Indian Migrants” in partial fulfillment of the requirements for the degree of Master of Science in Biology.

An abstract for Leah D’Aloisio’s thesis is included below.

Defences are open to all members of the campus community as well as the general public.

Registration is not required for in person defences.

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ABSTRACT

The growing immigrant population in North America are experiencing westernization at a rapid rate. Amidst the backdrop of rising immigration, health disparities are emerging in immigrants, including several modern diseases linked with the westernized lifestyle. Young Indian immigrants and Indo-Canadians face a significantly higher risk of inflammatory bowel disease (IBD) in westernized countries. While the root causes of IBD are not entirely understood, a main characteristic is an imbalanced gut microbiome no longer in symbiosis with its host. However, Indian populations are underrepresented in microbiome studies, making it challenging to determine the influences of their gut microbiome in this increased IBD risk. To understand why Indians are more vulnerable to IBD in Canada, it is essential to first investigate their gut microbiome.
This thesis explores the gut microbiome transition in Indian migrants in Canada by characterizing their microbial composition, and the impact of their dietary patterns on the microbiome. Using 16S and shotgun sequencing data obtained from stool samples of healthy subjects, our study compares the microbiome of Indians residing in India (also referred to as “Indian residents”), Indian immigrants to Canada (Indo-Immigrants), and their Canadian-born descendants (Indo-Canadians). Individuals born in Canada with European descent (Euro-Canadians) were used as a control, and immigrants born in a westernized country with European descent (Euro-Immigrants) were a westernized immigrant control. Our findings reveal significant differences in microbiota composition among these groups, with Indian residents showing a distinctive gut microbiota rich in Prevotella spp., whereas Indo-Canadians resembled more of an industrialized gut, with higher Bacteroides spp. abundance. While Indo-Immigrants had a gut microbiota that was distinct from Indians and westernized cohorts, some subjects displayed moderate levels of Prevotella spp. abundances, which may be due to their mixed diet that included both traditional Indian and westernized foods. This study concludes that Indo-Canadians undergo a marked transition towards an industrialized microbiome within just one generation, both through functional changes and the loss of Prevotella spp. This microbiota transition was associated with a large change in dietary habits, in particular a decrease in a high carbohydrate, high fiber diet, and an increase in ultra-processed foods. Overall, the data shown offers insight into how migration and lifestyle changes affect both microbial composition and functions in the gut, and their implications for understanding immigrant-health outcomes.