The Yanomami have the widest array of microbial genes yet found in a human gut (Image: Robin Hanbury-Tenison/Superstock)

The Yanomami people in the Venezuelan rainforest have the most diverse population of gut microbes ever seen, far more varied than Western guts. Does it matter?

Hunter-gathering in the rainforests and mountains of northern Brazil and southern Venezuela, the Yanomami eat a high-fibre diet based largely on cassava. For thousands of years, some groups have lived without contact with the rest of the world and are thought to be some of the few remaining communities never to have been exposed to antibiotics, which can wipe out the microbes in your gut.

So in some ways, the discovery, announced this week, that they carry the most diverse gut microbiomes ever documented is unsurprising. However, there is increasing evidence that our health is linked to the well-being of the microbes that call our gut home. So is the unspoilt, diverse ecosystem of the Yanomami something we should strive for?


Vaccination trip

Every year, the Venezuelan ministry of health visits newly identified communities to provide them with health services such as vaccinations, in part to protect them from diseases they could catch from gold miners that visit these regions. The decision to visit the particular Yanomami village that has now been studied was taken after it was spotted from the air in 2008.

Accompanied by interpreters who could explain the experiment in the Yanomami language, in 2009, scientists joined the medics and took mouth and forearm swabs and faecal samples from the villagers. The people they encountered had T-shirts and machetes and knew the Spanish word for “medicine”, but said they had never encountered non-Yanomami people before.

Sequencing the genes in the faecal samples revealed that the Yanomami carried nearly double the diversity of microbial species in their intestines compared with people living in the US. They also had about 30 to 40 per cent more diversity than a less isolated group of Venezuelan hunter-gatherers that has largely maintained its traditional lifestyle but has occasionally used antibiotics and eaten processed foods.

The Western way

“Our results suggest that Westernisation leads to the reduction of diversity, to different microbiota compositions,” Maria Dominguez-Bello of the New York University School of Medicine, who led the research, told a teleconference on Wednesday.

Her colleague Jose Clemente of the Icahn School of Medicine at Mount Sinai in New York, said the results suggest that even minimal exposure to modern lifestyle practices such as using antibacterial soaps and cleansers, taking antibiotics and having Caesarean sections, which mean babies don’t pass through their mother’s birth canal and pick up her microbes, can result in a dramatic loss of microbial biodiversity.

It can be difficult to disentangle which medical and lifestyle practices have the biggest impact on the microbiome says Jens Walter of the University of Alberta in Canada, who worked on both the Yanomami study and another one published this week that showed that the microbiomes of rural Papua New Guineans are also more diverse than those of US residents.

However, antibiotic use is high in Papua New Guinea, suggesting that it is other factors that are responsible for the relatively high microbiome diversity observed there.

Does it matter?

So does a more diverse microbiome make for a healthier person? Possibly. Healthier people do seem to host a more diverse array of microbes but it’s hard to know whether one causes the other. There is some evidence that losing certain microbial species is linked to some cancers, plus giving mice antibiotics can make them gain weight, so perhaps a good mix of microbes in your gut can keep you from piling on the pounds.

“It is an interesting hypothesis that the rise of Western diseases might be caused by the depletion of the gut microbiota,” says Walter. But it’s difficult to draw any conclusions about the benefits of microbial diversity by comparing ourselves directly with the Yanomami or Papua New Guineans because overall health and life expectancy is greater in modern societies.

Walter doesn’t recommend striving drastically to make the paltry Western gut look more Yanomamian. Poor sanitation is probably one factor contributing to the Papua New Guinean’s high microbial diversity, but they have high levels of infectious diarrhoea as a result – not a situation that Western urbanised nations would want to return to.

And a quick-fix method, like receiving a faecal transplant from a Yanomami person, would not be safe, says Walter. But restricting antibiotics and Caesareans to medically necessary cases can’t hurt, neither can eating more fibre, he suggests.

While visiting the village, the medics administered some antibiotics. Depending on the specific antibiotics given , one of the last remaining examples of a pre-antibiotic microbiome has probably already been sullied, says Björn Olsen of Uppsala University in Sweden. “It’s becoming harder and harder to find people like these Amerindians in our extremely urbanised world,” he says.

Journal references: Science Advances, DOI: 10.1126/sciadv.1500183 (Yanomami people); Cell Reports, DOI: 10.1016/j.celrep.2015.03.049 (Papua New Guineans)