Immigrants from Southeast Asia who arrive in the United States and undergo a rapid "westernization" of the bacteria in their gut, which could explain the increase in their rates of obesity and death. related diseases.

Researchers at the University of Minnesota have discovered this model by analyzing the digestive bacteria of 514 Hmong and Karen women – some still living in Southeast Asia, others recently arriving in Twin Cities and 39, other US-born immigrant children – and comparing them to the bacteria of 36 white women in Minnesota.

Six to nine months after arriving in the United States, immigrant women have experienced a decline in the number and diversity of their intestinal bacteria – essential to digestion and the health of the immune system – according to the study published in Cell, an influential scientific journal.

"Immigrants begin to lose their native microbes almost immediately after arriving in the United States, and then acquire exotic microbes that are more common among American Europeans," said Dan Knights, lead author of the study and quantitative biologist at the US. 'University.

The change was greater in obese immigrants and in US-born immigrant children. The dominant species of bacteria in their intestines have gone from Prevotella to Bacteroides, which are more common among Americans.

The diversity of their bacteria has also decreased, which is important because other studies have associated a lack of diversity with an increased risk of obesity, Knights said.

The intestinal microbiome is a new frontier of medicine. Recent studies have made remarkable discoveries about its diversity and influence on the rest of the body.

The study required a unique and substantial cooperation from the Twin Cities immigrant and refugee communities, which provided all the volunteers from the United States. Researchers certainly had to overcome language barriers and other barriers – such as the comfort level of immigrants for providing stool samples for bacterial testing – but found that the community was looking for solutions to the problem. of obesity.

"[The study] came at a time when rates of diabetes and obesity were at an extremely high level, "said Houa Vue-Her, who served as community consultant to the study. She also addressed Hmong health issues through her work at Blue Cross Prevention Center and Minnesota Blue Shield, which supports Hmong farmers in their efforts to introduce indigenous vegetables into schools.

"We saw [obesity] pick up and in our community we just want to know more about what's causing it, "she added.

The study included testing of a handful of Karen women who were in refugee camps in Thailand and then again in Minnesota.

Most surveys on obesity only ask people if they are Asian. There is therefore little data to prove that the problem is worsening among Americans Hmong. The Minnesota Student Survey, led by the state Department of Health, did not begin asking students that in 2016 they were Hmong. The results showed that 35% of Hmong high school students in Minnesota were overweight or obese, compared to 24% of whites.

There is little doubt about an obesity problem, as immigrants from Southeast Asia often switch from a diet rich in vegetables and rice to a high-fat American diet. They also adopted more sedentary lifestyles, showed research.

Dr. Tseganesh Selameab stated that she literally saw change in her patients at HealthCentre's International Health Center, where she often conducts initial screening of refugee health, and then monitors their health every year thereafter.

"By the time people come here, very few people are overweight, let alone obesity," she said. "The longer they have been there, the more they become obese. The conversations I have with them at age 10 or 20 are much more like conversations I have with Americans about diabetes and high blood pressure. "

Given these realities, Knights said he expects his study to find a change in the intestinal bacteria of arriving immigrants. But he is surprised at the speed of change and the fact that children have less diverse microbiomes than their immigrant parents.

"It was striking that this loss of diversity really happened in people who were changing countries or migrating from a developing country to the United States," he said.

Dietary changes do not seem to be the only explanation, as immigrants have not completely abandoned their original foods. The researchers followed their eating habits and found that they continued to consume more rice and vegetables than the Americans in the control group. And yet, their changes in intestinal bacteria were substantial anyway.

U's discovery shows how, even now, the gut microbiome is still poorly understood, Selameab said. Stress, air quality and other factors probably play a role.

The study does not prove that changes in intestinal bacteria cause obesity among immigrants, but only that there is a relationship between them, said Knights.

Further research is needed to determine whether a common strain of bacteria in Southeast Asia protects against obesity or whether a US strain helps to cause it.

"You could imagine isolating and cultivating some immigrant microbes that are usually present in healthy individuals in their group," Knights said. "These microbes could potentially be used as therapeutic products – somehow as medical grade probiotics.

"Before we get there, we need to determine whether microbial change is really the cause of obesity in this group, rather than just responding to obesity."