By comparing the gut bacteria of Amazonian hunter-gatherers to that of farmers and city dwellers, researchers have discovered a link between gut microbiota and lifestyle. The findings, published in Nature Communications this week, also revealed that we have far fewer kinds of gut microbes than traditional societies.
It's becoming increasingly clear that living more sanitized, urban lifestyles has led to our susceptibility to certain autoimmune disorders like asthma and allergies. Industrialization (and processed foods) has also led to a decrease in gut microbiome diversity. For example, the bacteria genus Treponema is conspicuously absent. Yet they've co-existed with humans and other primates for millions of years—making their absence now especially unsettling. Previous work have, however, found gut Treponema in members of traditional societies who only eat local, non-industrially produced foods.
Now, University of Oklahoma’s Cecil Lewis and colleagues analyzed the gut microbiota in fecal samples from 25 Matses—a hunting-gathering community living in the Peruvian Amazon—as well as 31 small-scale farmers from the village of Tunapunco in the Andean highlands and 23 city dwellers in Norman, Oklahoma. Then they compared data on these three different lifestyles—traditional hunter-gatherers, traditional agriculturalists, and urban-industrialized peoples—with previously published studies on populations in Africa and South America.
Their comparisons revealed a striking trend: Gut microbiota cluster together on the basis of subsistence strategy, not on how close they are geographically. Hunter-gatherers in South America and Africa are more similar to each other than either of them are to rural farmers or to urbanites—even if they live in neighboring areas.
Furthermore, the team detected several (non-pathogenic) strains of gut Treponema—suggesting how these are symbionts that have been lost in urban-industrialized populations. Some of these were similar to Treponema succinifaciens, which are known to help pigs metabolize carbohydrates. "We show that these lost bacteria are in fact multiple species that are likely capable of fermenting fiber and generating short chain fatty acids in the gut. Short chain fatty acids have anti-inflammatory properties,” Lewis explains in a news release. “This raises an important question, could these lost Treponema be keystone species that explain the increased risk for autoimmunce disorders in industrialized people?” They hope to explore that next.
After the researchers’ visit to the Matses, the hunter-gatherers have begun to shift their diet to one that includes industrial food. “It is possible that their current profile is changing, and we have a unique opportunity to appreciate the biological impact of urban transition in the gut microbiome," study author Alexandra Obregon-Tito from University of Oklahoma says. "Studying native human communities provides an opportunity to explore human biological phenomena that might have disappeared in western societies; however, we need to be conscious of the challenges of working with vulnerable human populations.”