Immigrants arrive with flourishing gut microbes. Then America's diet trashes them

An empire of germs dwells inside you, trillions strong. About a half-pound of bacteria plus their genes make up our microbiome. Though each microbe is small, a healthy and diverse microbiome is mighty. Its influence, studies suggest, spans the human condition — from mood swings to weight gain.

The microbiome begins as a departing gift from mothers at birth, but many factors alter its composition. Growing evidence shows location has a profound impact on the diversity of microbes, and some places are much worse than others. A new study, published this week in the journal Cell, follows multi-generation immigrants from Southeast Asia to the United States. As they moved, their microbes responded. Once in the United States, the immigrants' gut diversity dropped to resemble the less-varied microbiomes in European Americans. At the same time, obesity rates spiked.

“We found that moving to a new country changes your microbiome,” said Dan Knights, a computational microbiologist at the University of Minnesota and an author of the paper. “You pick up the microbiome of the new country and possibly some of the new disease risks that are more common in that country.”

In the United States, immigrants in the study ate foods richer in sugars, fats and protein. Microbiomes changed within months of moving. “People began to lose their native microbes almost immediately after arriving in the U.S.," Knights said. “The loss of diversity was quite pronounced: Just coming to the USA, just living in the USA, was associated with a loss of about 15 percent of microbiome diversity.”

Obesity rates among many of the study immigrants increased sixfold. Those who became obese also lost an additional 10 percent of their diversity. “And the children of immigrants,” Knights said, “had yet again another 5 to 10 percent loss.”

https://www.washingtonpost.com/science/2018/11/02/immigrants-arrive-with-flourishing-gut-microbes-then-americas-diet-trashes-them/