Research in Nepal shows that microbes in the mouth reflect lifestyle choices

Lifestyle can determine the composition of beneficial bacteria and other microorganisms in the mouth, according to a new study led by Penn State biologists. The international team revealed how the oral microbiome differs across a range of subsistence strategies – from nomadic hunter-gatherers to farmers to industrialized groups – and found that lifestyle, as well as specific lifestyle factors such as smoking, can shape the microbiome. A paper describing the results will be published on November 4 the news Microbiome.

A healthy oral microbiome, a community of microorganisms that live in the mouth, plays an important role in aiding the digestion of food, supporting the immune system and protecting against invading pathogens, while an unhealthy oral microbiome is associated associated with a variety of human diseases.

“The oral microbiome is under-researched, and most studies of the oral microbiome have been conducted in Western populations,” said Emily Davenport, assistant professor of biology at Penn State Eberly College of Science and leader of the research team. “Although we have learned a lot from that, microbiomes look different all over the world. By studying how the diversity and composition of the oral microbiome varies with lifestyle in a global context, we can improve our knowledge of how the oral microbiome influences human health. “

In a study of 63 Nepalese individuals representing a spectrum of dietary practices, researchers examined how important lifestyle factors such as livelihood strategy (how one obtains the necessities of life such as food and shelter) and more specific factors and behaviors, such as smoking, can contribute to disparities in the microbiomes between populations.

“We know from previous studies that there are differences in the microbiome between individuals living in highly industrialized, Westernized societies and those who are nomadic hunter-gatherers, but there is a broad spectrum of lifestyles in between,” said Erica Ryu, graduate student at the University of California. biology at Penn State Eberly College of Science and first author of the paper.

‘Our understanding of these relationships has thus far been clouded by geography; it is difficult to make statements about the impact of lifestyles when you compare people in different countries with, for example, different climates, access to medical care and exposure to diseases. In this study, we comprehensively investigated the oral microbiome of individuals with different lifestyles from the same country, Nepal.”

The researchers studied the oral microbiomes of people from groups with different subsistence strategies. These included foragers, who are hunters and gatherers and may not live in one location all year round; subsistence farmers who are hunter-gatherers from groups that have recently settled and started farming within the last fifty years; farmers from groups that have been dependent on agriculture for centuries; industrialists, expats from Nepal who have immigrated to the United States over the past twenty years; as well as a group of industrialists born in the same area of ​​the United States for comparison. They also asked a variety of questions about lifestyle, including diet, education, medical practices and other behaviors.

The researchers sequenced the DNA of the microbes in saliva samples to determine the specific bacterial species in each individual’s oral microbiome. They found that the composition of species within the oral microbiome tended to follow the gradient of subsistence strategies, with some specific species being more prominent among foragers and one species more prominent among industrialists, suggesting that lifestyle does indeed influence the oral microbiome.

Furthermore, the presence of different types of microbes was linked to specific lifestyle factors, including smoking, the prominent type of grains in an individual’s diet – barley and corn versus rice and wheat – and the consumption of a plant called nettle. The researchers note that previous research has consistently linked smoking to the composition of the oral microbiome in industrialized populations, and collectively this suggests that smoking habits play an important role in determining the oral microbiome in a variety of lifestyles.

“It makes sense that different microbes feed on the different grains in a person’s diet, but it’s interesting that we also see a connection with sisnu, also called nettle,” Davenport said. “Nettle is a fibrous plant that is often chewed by the foragers in this study, much like humans chew gum. Given the important role it plays in Nepalese cuisine, culture and medicine, it is interesting to see that it is associated with oral microbes.”

The researchers emphasized the importance of including lifestyle factors and behavior in future microbiome studies, as well as involving populations from around the world.

“We studied populations in Nepal because it provided a unique way to examine the effects of lifestyle, while controlling for a variety of other factors, such as geography, that often obscure that effect,” Davenport said. “But it highlights the impact of lifestyle factors that are likely at play in other populations.

“Any time you make a change – whether it’s a different diet, a different location or a different culture – the microbiome can also change, and it’s important to understand to what extent and how quickly these changes occur ,” she added. “Continuing to investigate how oral microbiomes vary around the world will improve our understanding of what exactly makes up the microbiome and how it affects human health.”