Immigration to the United States can trigger a swift and radical change in the population of bacteria living in the human gut, according to a study of people who moved from Thailand to Minnesota.
Dan Knights at the University of Minnesota in Minneapolis and his colleagues studied the gut bacteria of women belonging to the Hmong and Karen ethnic groups who had left Asia for the Minneapolis area. The researchers also sampled the gut microbes of 19 Karen women either before or soon after their move to the United States, as well as in the following months.
The team found that the immigrants’ characteristic gut microbes were rapidly replaced by organisms common in a European–American control group. This shift may have affected the immigrants’ ability to digest certain plants frequently eaten in Southeast Asia. The diversity of the immigrants’ gut flora also fell sharply.
The gut microbes of the Karen women began to give way to US microbes within 6–9 months of arrival, the authors found.