A recent study by researchers from the University of Minnesota provides evidence that the gut bacteria—or "microbiome"—of Asian populations, specifically Hmong and Karen communities, is radically altered for the worse upon migrating to the United States. They speculate with these findings that other immigrant populations in the U.S. are also suffering from similar disruptions to the microbiome.

Poor gut health is associated with higher risk for chronic disease and obesity. Individuals who have a more diverse microbiome are at lower risk for obesity, diabetes and many chronic diseases.

However, findings from our own research on Mexican and Central American immigration, food insecurity and food systems in the U.S. and Mexico tell a larger story.

We have found that the political and economic structures and arrangements that shape local environments and force people to migrate, also influence health behaviors and outcomes both in sending and receiving migrant contexts. In other words, perhaps we should worry about “macro” as much as microbiomes.

Our research findings help to explain how factors like national and local politics, immigration policies and the economy impact the health of people before and after they migrate to the U.S.

Immigrant gut health is not simply a matter of what foods individuals choose to eat. Contrary to popular belief, a variety of political, economic and social factors can constrain people's access to healthy foods for a prolonged period of time. Researchers and policymakers call this "food insecurity."

Compared to U.S.-born citizens, immigrants—especially individuals of undocumented or temporary status—are more likely to experience heightened levels of food insecurity.

Immigrants often work in low-wage occupations that hinder their purchasing power, meaning that they have less money to buy healthier, more expensive foods. In one of our studies on food insecurity among Mexican and Central American migrant women in Santa Barbara, Calif., women often cited constraints on the household food budget from unemployment and underemployment in low-paying, seasonal jobs such as housekeeping, construction and agriculture.

In addition, immigrants face barriers to accessing public assistance such as the Supplemental Nutrition Assistance Program (SNAP)—formerly known as food stamps. The Personal Responsibility and Work Reconciliation Act of 1996 barred immigrants from being able to utilize federal welfare programs. Although immigrant households with U.S.-born children qualify for SNAP, many are scared to enroll in SNAP benefits out of fear of jeopardizing their petitions for legal status.

Policies that restrict immigrants' use of various forms of welfare (including SNAP) can be an additional source of exclusion as well as stress. Restrictive immigration policies can thus portend very real consequences for immigrant gut health, both by constraining access to healthy food and by rendering anxieties that, over time, exacerbate risks for chronic disease. Research on the syndemics of immigrant health shows that the interaction of emotional stress, institutionalized forms of exclusion, exposure to violence, and depression can induce chronic stress and translate to poor health outcomes.


Coming to the U.S. isn't the only way in which we're seeing large disruptions in food-related health issues. As the standard American diet (SAD) spreads beyond U.S. borders as a result of trade agreements and globalization, poor gut health and the incidence of noncommunicable disease have risen rapidly in other countries.

The North American Free Trade Agreement (revised and renamed the USMCA and signed as such in December 2018) is a prime example of one such political and economic factor that has had a significant impact on the way people eat in North America. A deal that lowers barriers to trade in the US, Canada and Mexico, NAFTA has facilitated the transformation of diets across the continent, with everyone eating more food made in factories.

Global trade agreements such as NAFTA enable multinational food and beverage corporations such as Coca Cola, Pepsico, Kraft and Bimbo to distribute highly processed foods even in the most rural, isolated places and make it harder for people to live on and off of the land.


Mexicans now eat fewer corn tortillas and more corn chips and beverages sweetened with corn syrup. A shift from the ancestral corn-based diet means that people consume more sugar, fat, and the chemicals used in food processing, and fewer fresh foods associated with gut health. This produces, paradoxically, an excess of calories and a lack of micronutrients, so people can be malnourished even while their caloric intake is high. This is part and parcel of the displacement from the countryside and rural ways of life that drives migration and starts a cycle of stress and often trauma.

While immigrant health has been seen to decline with greater duration of time spent in the U.S. and assimilation to the diet known as the SAD, today it is not necessary to migrate to eat like an American. Even those who never migrate are eating the SAD, and exposed to the same die-off of gut bacteria and loss of ancestral ways of eating.

Restoring gut health and biodiversity (and undoing chronic disease) entails multiple planes of action, many of them at the scale of policy. Perhaps instead of continuing with the mantra of “you are what you eat,” it would behoove us to account for the political and economic structures that both shape what we eat and determine which microbes stick around.