The Americanization Of The Gut: The Death of Diversity

by Henri Roca, MD, Clinical Functional Medicine Specialist

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I wonder if you may have noticed if you’ve traveled to other countries that their populations are generally thinner than those in the United States. Maybe you’ve noticed that same situation with newly arriving immigrants.

Becoming an American generally makes a person heavier and less healthy. As other countries have come to adopt our western ways of living – specifically eating a diet rich in calorically dense and nutritionally deficient processed and prepared foods, moving less, and having more stress – their indigenous populations also become heavier and less healthy.

I remember in 1997, when I completed an elective rotation in International and Indigenous Medicine in Ghana , their public health officials were starting to raise the alarm. For the first time in history (since the evolution of humans on the African continent, or at least since records had been kept) deaths caused by infections were being overtaken with deaths due to chronic diseases like cancer, obesity, diabetes, and heart disease. Because interventions addressing infections, particularly malaria, were becoming more widespread and effective, people were living longer. As populations began to increase their caloric intake of more prepared and less fresh foods, their diets began to affect their health.

This study gives us a possible reason for these observations. Almost immediately as immigrants arrive in the US and their diet changes, their gut bacteria changes. Microbial diversity decreases substantially and measurably. Those bacteria that most effectively metabolize complex carbohydrates reduce substantially. The flora shifts from Prevotella dominance to Bacteroids dominance and these changes propagate across generations.

While this study cannot draw a direct correlation between these flora changes and obesity, it is impressive that staying in the US for as little as ten days can shift how our guts work. Indeed, the changes in gut flora composition are likely due to a complex set of circumstances including stress, low exercise, antibiotic use, water supply, and treatment of parasitic infections in addition to diet.

Given this finding, I am led to wonder if the westernization of the gut flora might also explain, at least in part, the ill health of Native American populations as they moved from a more free range lifestyle to a dependent reservation-based life or to the ill health of folks in rural Appalachia who were the initial recipients of government provided food in the 1960s (processed cheese food, powdered milk, white flour, canned meat, sugar), or other populations that moved from an agricultural lifestyle to an industrial lifestyle.

We are literally what we eat.

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