Study: US Immigration Changes Gut Bacteria and Weight

New country? New gut. That’s according to one study, that shows when a person moves to the U.S., they immediately begin losing some of their native gut bacteria.

Researchers analyzed the bacteria of 500 women who immigrated from Southeast Asia to Thailand and the U.S., including first- and second-generation immigrants. Their bacteria was then compared to that of Caucasian Americans. Scientists discovered that a particular Western bacteria strain began to displace the non-Western strain within their first six to nine months in the U.S.. They also lost more types of microbes than they gained, leaving the women with a less diverse microbiome.

The longer the immigrants spent in the U.S., the more their microbiomes diverged from those of ethically similar people living in Thailand. Additionally, the children of immigrants had microbiomes most similar to Caucasian Americans.

Researchers also looked closely at the participants’ food logs. They found that the American diet – featuring less fiber and more processed sugars – likely played a role in changing the immigrants’ microbiomes. That’s because some of the bacteria in our gut survive on particular plant fibers. Once that source is gone, those organisms die off.

In addition to diet, scientists believe other factors could have also played a role in the gut’s bacterial changes.

“Exposure to different medications, especially antibiotics or changes in the quality of water they're drinking, are also affecting their microbiomes," says Pajau Vangay, a researcher at the University of Minnesota who co-authored the study.

Scientists are still trying to figure out what influence diet and gut bacteria have on obesity. This new information could help explain why immigrants and refugees are particularly vulnerable to unhealthy weight gain over a short period of time.

With the new explosion of health probiotic products now available, immigrants may find value in adding these to their daily regimen as well as well as opting to eat a healthier diet with increased levels of health plant fiber.