<p id="P3">Many United States immigrant populations develop metabolic diseases post-immigration,
but the causes are not well understood. Although the microbiome plays a role in metabolic
disease, there have been no studies measuring the effects of U.S. immigration on the
gut microbiome. We collected stool, dietary recalls, and anthropometrics from 514
Hmong and Karen individuals living in Thailand and the U.S., including first- and
second-generation immigrants and 19 Karen individuals sampled before and after immigration,
as well as from 36 U.S.-born European American individuals. Using 16S and deep shotgun
metagenomic DNA sequencing, we found that migration from a non-Western country to
the U.S. is associated with immediate loss of gut microbiome diversity and function,
in which U.S.-associated strains and functions displace native strains and functions.
These effects increase with duration of U.S. residence, and are compounded by obesity
and across generations.
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