Go to the United States with your intestinal bacteria

Sitting in a new country can be a challenge, not only for us, but also for our bacteria. A new compelling study published in Cell suggests that migration between certain countries can profoundly affect the bacteria that live in our digestive system, with important implications for our health.

We know that immigrants to the United States are more likely to develop obesity and metabolic diseases such as diabetes than people from the same countries that do not emigrate or native-born US citizens, but we do understand not really why. To try to understand this phenomenon from a health perspective, researchers at the University of Minnesota have conducted extensive in-depth study of Chinese and Thai immigrants settling in the United States. The authors examined diet, intestinal microbes and body mass index of immigrants. before and after their move. The evidence showed that the more time immigrants spent in the United States, the less their bacteria diversified and this was related to an increase in obesity.

The human gut houses hundreds of different species of bacteria known as the 'intestinal microbiome'. In addition to breaking down food, this community of microorganisms helps our body fight and prevent disease. It is even temptingly proven that the gut microbiome can affect our mental health.

A more diverse intestinal microbiome is associated with a healthier digestive system. And the factors that reduce this diversity, such as antibiotics, stress, or diet changes, can make us more vulnerable to diseases such as obesity or irritable bowel disease.

File photo: An artist image of bacteria in the small intestine. Getty Images

The study compared a total of 514 healthy women, divided between those born and residing in Thailand, those born in Southeast Asia who later moved to the United States and those born in the United States of immigrant parents from Southeast Asia. He found that changes in the gut microbiome began as immigrants arrived in the United States and continued to change over the decades. The longer they lived there, the more their microbiomes resembled those born in the country, of European ethnicity. The majority of participants living in the United States also gained weight during the study.

The combination of species that make up our intestinal microbiomes is strongly influenced by our diet. As a result, people from different parts of the world tend to have different bacteria. Western guts usually contain a lot of Bacteroides species, which digest animal fats and proteins. The guts of people with a non-western diet rich in plants tend to be dominated by Prevotella species, which are good for digesting plant fiber. The new study found that strains of bacteria from countries of origin of immigrants, particularly Prevotella species, have been completely lost, as well as enzymes necessary for the digestion of important plant fibers.

Cause or effect?

Studies that suggest that the microbiome can affect human health or disease are often disputed because it is difficult to distinguish between cause and effect. In this case, it is unclear whether changes in the microbiome directly contribute to the high incidence of obesity among US immigrants. It may take some time to fully understand if a less diverse microbiome leads to obesity or if obesity leads to a less diverse microbiome.

Most of our knowledge in this field comes from the study of laboratory mice. Innovative studies conducted by American biologist Jeff Gordon, an American biologist, found a link between obesity and the gut microbiome in 2006, when they showed that mice gain weight when they were receiving an intestinal bacterium of obese obesity. But we also know that diets high in fat are the cause of obesity, no matter what is in the gut microbiota. It would be premature to think that only the microbiome is responsible for obesity.

Photo of file: Slices of meat are illustrated. Western guts usually contain many species of Bacteroides, which digest fats and animal proteins well. Getty Images

With increasing immigration and changing dietary habits, it is important that we better understand how changes in populations, cultures and diets can impact human microbiomes in order to detect potential health problems. For example, we know that refugees, especially children, are more likely to develop obesity. We must therefore develop new strategies to combat this.

Education is one aspect and another is the fight against poverty, which is generally more common among immigrants than among native-born citizens. But if the gut microbiome is really at the heart of health and disease, it might be useful to find a way to treat it directly by prescribing drugs such as probiotics or even stool transplants. One day, we could even have microbial "pills" that could help migrants fight against changes in their gut microbiome and move to a healthier home.

Chloe James is a senior lecturer in medical microbiology at the University of Salford, Manchester, UK, and Ian Goodhead is a lecturer in infectious diseases, also at the University of Salford.

This article is republished from The Conversation under a Creative Commons license. Read the original article.