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According to a new study by researchers at the Stanford University School of Medicine and their collaborators, the intestinal bacteria of four Himalayan populations differ in their dietary lifestyles.
The four populations – Tharu, Raute, Raji and Chepang – have long resided in the foothills of the Himalayas, with similar languages, cultural practices and ancestors. The history of their diet divides the four: the Tharu practice agriculture for 250 to 300 years; Raut and Raji have practiced agriculture for 30 or 40 years; and the Chepang are hunter-gatherers. The study found that the composition of intestinal microorganisms, or intestinal microbiome, of each population differed according to whether the hunter-gatherer life group had left its lifestyle and for how long.
"This study indicates that human microbiomes may have changed gradually with the human lifestyle, and that these changes may occur over the course of life," said Aashish Jha, Ph.D., postdoctoral researcher. at Stanford and lead author of the study.
The results will be published on November 15 in PLOS Biology.
Previous research has revealed clear differences between intestinal microbiomes of indigenous populations in Africa and South America and those of western industrialized populations in Europe and the United States. However, this study is the first to show a change in the composition of the intestinal microbiome between closely related populations living in the same geographical area.
An evolving gut
In each of our intestines lives a community of thousands of billions of bacteria that make up our intestinal microbiome. These bacterial communities are essential for the digestion of food and the regulation of our immune system. They begin to colonize immediately after birth and grow at a staggering rate once we start interacting with our environment. As we grow up, our exposure to breast milk, soft foods and possibly fruit, vegetables and solid meats helps the intestines to establish a complex microbiome that plays a crucial role in maintaining human health.
For most of our history, our guts have been exposed only to wild foods available in our environment. Some 1.8 million years ago, at the time of Homo erectus, humans were a nomadic species of hunter-gatherers whose diet consisted of fish and seafood. meat, as well as seasonal seeds, nuts, roots, vegetables and berries. It was not until about 10,000 years ago that we switched to agriculture, drastically altering our diet, cooking techniques, and way of life.
To examine whether this lifestyle change affected the composition of the intestinal microbiome, the researchers collected stool samples from 56 individuals belonging to the four populations of the Himalayas and from 10 individuals belonging to a North American control group. European origin. These samples were collected over a two-month period. The researchers also collected information on demographic characteristics, dietary practices, health status, drugs, smoking and alcohol use, as well as on several other environmental variables for to determine how lifestyle changes in the four Himalayan populations correlated with differences in intestinal microbiomes. .
An analysis of the contents of the samples revealed four distinct types of intestinal microbiome. Even more exciting, these distinctions have been paralleled by the shift from hunter-gatherer populations to farmers. The researchers found that subdivisions of bacteria, including Ruminobacter and Treponema, which abound in feeding groups such as Chepang, are declining as populations move away from the hunter-gatherer way of life. In fully industrialized populations, such as those in North America, these bacteria are rare or completely absent. Conversely, strains of other bacterial phyla, such as Actinobacteria and Verrucomicrobia, are rare or non-existent in hunter-gatherers, but appear at the moment when agriculture and industrialization take root.
With Raute and Raji switching to agriculture over the past 30 to 40 years, these results also suggest that pronounced changes in intestinal microbiomes can occur in the decades following the hunter-gatherer lifestyle change. .
A 2017 scientific study led by Justin Sonnenburg, Ph.D., an associate professor of microbiology and immunology at Stanford, also showed significant changes in the intestinal microbiome in a hunter-gatherer society called Hadza. Researchers found that Hadza intestinal bacteria was linked to their seasonal diet. Together with the current study, these results "really speak to the power of food on changing the microbiota," said Sonnenburg, lead author of the new paper.
Our microbial identity
With the intestinal microbiome so easily influenced, Sonnenburg wonders what that means for our definition of human biology.
"We have always thought about humans as human DNA and the collection of human cells we walk with," he said. "But we now know that we have this microbial identity and that the microbial part of our biology is malleable. This can change in a very short time. "
Investigators are still working to find out what dietary factors and other factors contribute to this transformation. So far, they have strong evidence suggesting a correlation between village drinking water sources and differences in intestinal bacteria. This information may be useful for future studies to examine direct environmental influences on intestinal health.
The next step is to develop a more detailed survey that will identify particular dietary components, in each of the four populations of the Himalayas, which are associated with changes in the intestinal microbiome.
Jha feels a sense of urgency to carry out this research. "While the world is rapidly urbanizing, our microbiomes are also evolving rapidly," he said. "So, if we do not study traditional societies today, in 20 years we may be too late."
According to a new study by researchers at the Stanford University School of Medicine and their collaborators, the intestinal bacteria of four Himalayan populations differ in their dietary lifestyles.
The four populations – Tharu, Raute, Raji and Chepang – have long resided in the foothills of the Himalayas, with similar languages, cultural practices and ancestors. The history of their diet divides the four: the Tharu practice agriculture for 250 to 300 years; Raut and Raji have practiced agriculture for 30 or 40 years; and the Chepang are hunter-gatherers. The study found that the composition of intestinal microorganisms, or intestinal microbiome, of each population differed according to whether the hunter-gatherer life group had left its lifestyle and for how long.
"This study indicates that human microbiomes may have changed gradually with the human lifestyle, and that these changes may occur over the course of life," said Aashish Jha, Ph.D., postdoctoral researcher. at Stanford and lead author of the study.
The results will be published on November 15 in PLOS Biology.
Previous research has revealed clear differences between intestinal microbiomes of indigenous populations in Africa and South America and those of western industrialized populations in Europe and the United States. However, this study is the first to show a change in the composition of the intestinal microbiome between closely related populations living in the same geographical area.
An evolving gut
In each of our intestines lives a community of thousands of billions of bacteria that make up our intestinal microbiome. These bacterial communities are essential for the digestion of food and the regulation of our immune system. They begin to colonize immediately after birth and grow at a staggering rate once we start interacting with our environment. As we grow up, our exposure to breast milk, soft foods and possibly fruit, vegetables and solid meats helps the intestines to establish a complex microbiome that plays a crucial role in maintaining human health.
For most of our history, our guts have been exposed only to wild foods available in our environment. Some 1.8 million years ago, at the time of Homo erectus, humans were a nomadic species of hunter-gatherers whose diet consisted of fish and seafood. meat, as well as seasonal seeds, nuts, roots, vegetables and berries. It was not until about 10,000 years ago that we switched to agriculture, drastically altering our diet, cooking techniques, and way of life.
To examine whether this lifestyle change affected the composition of the intestinal microbiome, the researchers collected stool samples from 56 individuals belonging to the four populations of the Himalayas and from 10 individuals belonging to a North American control group. European origin. These samples were collected over a two-month period. The researchers also collected information on demographic characteristics, dietary practices, health status, drugs, smoking and alcohol use, as well as on several other environmental variables for to determine how lifestyle changes in the four Himalayan populations correlated with differences in intestinal microbiomes. .
An analysis of the contents of the samples revealed four distinct types of intestinal microbiome. Even more exciting, these distinctions have been paralleled by the shift from hunter-gatherer populations to farmers. The researchers found that subdivisions of bacteria, including Ruminobacter and Treponema, which abound in feeding groups such as Chepang, are declining as populations move away from the hunter-gatherer way of life. In fully industrialized populations, such as those in North America, these bacteria are rare or completely absent. Conversely, strains of other bacterial phyla, such as Actinobacteria and Verrucomicrobia, are rare or non-existent in hunter-gatherers, but appear at the moment when agriculture and industrialization take root.
With Raute and Raji switching to agriculture over the past 30 to 40 years, these results also suggest that pronounced changes in intestinal microbiomes can occur in the decades following the hunter-gatherer lifestyle change. .
A 2017 scientific study led by Justin Sonnenburg, Ph.D., an associate professor of microbiology and immunology at Stanford, also showed significant changes in the intestinal microbiome in a hunter-gatherer society called Hadza. Researchers found that Hadza intestinal bacteria was linked to their seasonal diet. Together with the current study, these results "really speak to the power of food on changing the microbiota," said Sonnenburg, lead author of the new paper.
Our microbial identity
With the intestinal microbiome so easily influenced, Sonnenburg wonders what that means for our definition of human biology.
"We have always thought about humans as human DNA and the collection of human cells we walk with," he said. "But we now know that we have this microbial identity and that the microbial part of our biology is malleable. This can change in a very short time. "
Investigators are still working to find out what dietary factors and other factors contribute to this transformation. So far, they have strong evidence suggesting a correlation between village drinking water sources and differences in intestinal bacteria. This information may be useful for future studies to examine direct environmental influences on intestinal health.
The next step is to develop a more detailed survey that will identify particular dietary components, in each of the four populations of the Himalayas, which are associated with changes in the intestinal microbiome.
Jha feels a sense of urgency to carry out this research. "While the world is rapidly urbanizing, our microbiomes are also evolving rapidly," he said. "So, if we do not study traditional societies today, in 20 years we may be too late."
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