Westernized diets are reshaping immigrant gut microbiomes

A recent study conducted by researchers at UBC Okanagan revealed that Indo-Canadians, individuals with Indian descent born in Canada, undergo significant changes in their gut microbiome as they adopt more westernized diets.

These changes could potentially explain the higher prevalence of inflammatory bowel disease (IBD) among South Asian immigrants in Canada.

Leah D’Aloisio, a Master of Science graduate at UBC Okanagan and the lead author of the study, stated, “Many non-European populations are not well represented in microbiome research. By studying Indo-Canadian immigrants, we can gain insights into how dietary shifts impact gut health and chronic disease prevention.”

The research, published in npj Biofilms and Microbiomes, compared stool samples and dietary habits of over 170 participants in India and Canada, including individuals from various backgrounds such as Indians living in India, first-generation Indian immigrants, Indo-Canadians, Euro-Canadians, and Euro-immigrant controls.

Compared to individuals in India, both Indo-Canadians and first-generation Indian immigrants exhibited alterations in their gut microbiomes and dietary patterns, with the most significant changes observed in Indo-Canadians.

The study involved collaboration with researchers from Canada, India, the U.K., and the U.S., and the results indicated that while individuals in India maintained gut bacteria associated with a high-fiber, plant-based diet, Indo-Canadians displayed a “transitional” microbiome characterized by a decline in beneficial Prevotella species and an increase in markers of a westernized gut ecosystem.

Impact of Westernization on Health Risks

Global populations, including Indians, experience a higher incidence of IBD following migration. In Canada, South Asians have a more than six-fold increased risk of IBD compared to individuals in India.

The researchers suggested that dietary acculturation, which involves a shift towards processed foods high in sugar and additives and away from fiber-rich traditional diets, plays a significant role in altering the gut microbiome.

Dr. Deanna Gibson, a Biology Professor at UBC Okanagan and senior author of the study, emphasized, “Our findings indicate that the gut microbiome adapts not only to environmental factors but also to dietary changes. For Indo-Canadians, this adaptation results in a microbiome that reflects a blend of traditional and western influences, potentially contributing to the increased disease risk observed in individuals born in Canada with Indian heritage.”

Key Findings of the Study

• Individuals in India exhibited a gut microbiome enriched with Prevotella, a bacteria known for metabolizing complex plant-based carbohydrates and dietary fiber.
• Immigrants and Indo-Canadians displayed a decrease in Prevotella and an increase in microbes commonly found in western populations, such as Blautia and Anaerostipes.
• Diet analysis revealed that over 60% of daily calories consumed by Indo-Canadians came from ultra-processed foods, in contrast to just 12% in India. Fiber intake was highest in India and lowest among Indo-Canadians.

Dr. Gibson advised, “Individuals in India should consider sticking to their traditional dietary patterns. The rapid changes in the food industry in India are likely to contribute to a shift towards westernized gut microbiomes and subsequently increased risks of diseases like IBD. The rising prevalence of IBD in recent years in India is undoubtedly linked to the westernization of diets.”

Implications of Western Diets on a Global Scale

These findings underscore how migration, globalization, and dietary choices influence long-term health risks. The researchers emphasized that these observations are not exclusive to Indian populations.

As diets become more industrialized worldwide, the gut microbiome serves as a valuable indicator of how health risks are transmitted through migration and cultural transformations.

With increasing global mobility and the industrialization of diets, the researchers advocate for the development of culturally relevant dietary guidelines and health strategies tailored to immigrant populations.

Leah D’Aloisio added, “While the exact causes of IBD remain unclear, the rapid emergence of risk factors in immigrant communities provides an opportunity to identify the drivers of disease and support efforts to preserve beneficial dietary traditions.”