The Yanomami and the world’s most robust intestinal flora

Having lived in isolation from the western world for around 11,000 years, the Yanomami – a South American tribe – have been shown to have the world’s most robust intestinal flora. Their uniquely diverse intestinal bacteria is in fact double the size of ours in the West. By studying the Yanomami’s intestinal flora, scientists have begun to trace how much of an influence our Western diet and lifestyle have on both our intestinal flora and our well-being.

Yanomami lived in isolation from the western world

The South American Yanomami tribe live in the Amazon rainforest border country between Brazil and Venezuela. They live in large, round houses called ‘yanos’ or ‘shobanos’, mostly built of palm leaves and wood. One yano can house up to 400 people and is often home to a whole community. Every family has its own separate section, while there is also a large, shared space for rituals, parties, and play.

The members of the tribe are hunter-gatherers, with the men usually hunting and the women taking care of vegetable plots where they grow around 60 different plants. Meat makes up around 10% of their diet, with the rest being plant foods. The meat comes from wild animals that live in the rainforest – usually birds and small mammals but also small crabs, frogs, and fish from nearby waterways. The Yanomami diet consists of varied seasonal fruits and vegetables such as wild bananas, palm hearts, and cassava, making it rich in both vitamins and dietary fibre.

The Yanomami people encountered the outside world for the first time in the 1960s. It was then estimated that they had lived in isolation for about 11,000 years. Contact with the outside world led to the spread of infectious diseases, which they did not have immunity to. Hence, a large part of the population died. However, there are still villages in the mountainous areas that are isolated. In 2008, a previously unknown village was discovered by an army helicopter, and the following year a study was initiated on 34 volunteers aged 4 – 50 years to make detailed analyzes of the tribe´s microbial DNA.

The world’s most robust intestinal flora

When scientists studied the Yanomami’s intestinal flora, they found the greatest diversity of intestinal bacteria they had ever measured in a single group of people. Some studies additionally show that their robust intestinal flora could well be linked to their lifestyle as well as to the absence of western medicine. In the light of the Yanomami ’s intestinal flora exhibiting twice the diversity that we have in the western world, scientists have begun questioning what ours might be lacking and what consequences this could have for our health.

Scientists studying the Yanomami also reported that the members of the tribe did not suffer from auto-immune diseases, diabetes or high blood pressure. Professor Stig Bengmark has had a long-standing interest in the Yanomami, and in his chapter in the book, Inflammation: From Molecular and Cellular Mechanisms to the Clinic (2017), he came to the conclusion that ‘These observations support the theory that a large number of the diseases we have in the West, but which are rare in the rural areas of Africa and South America, are a result of comprehensive diet and lifestyle changes’.

Additional studies have shown that lifestyle changes from traditional hunter-gatherer societies to our current western society have influenced the development of our intestinal flora. It has been shown that people who live in hunter-gatherer societies or as farmers in the countryside have a noticeably larger diversity of beneficial bacteria in their intestinal flora than people in urban and industrial environments.

The Yanomami showed a natural resistance to antibiotics

When the Yanomami’s intestinal flora was examined, scientists made an unexpected, simultaneous discovery: they identified genes that code for resistance to antibiotics. Even if these genes were not activated, they indicate a resistance both to natural antibiotics found in the soil and, in all probability, to chemically-produced antibiotics such as medicines.

Lifestyle influences intestinal flora and health

Aspects of our lifestyle, everything from high stress levels and rigorous hygiene procedures to lots of processed food, are all contributing factors in relation to reduced diversity of beneficial bacteria in the intestinal flora. Diet plays a decisive role – both for the intestinal flora and for us to stay healthy. Studies show that the amount of fruit and vegetables that we eat every day is very important, and that eating a variety has a positive effect on the bacteria in our intestines. Processed food, however, which is high in calories, sugar, and additives but also low in nutrition, is good for neither the intestinal flora nor our general health. Maybe we could all learn something from the Yanomami and their way of life?


Clemente, J. C., Pehrsson, E. C., Blaser, M. J., Sandhu, K., Gao, Z., Wang, B., Magris, M., Hidalgo, G., Contreras, M., Noya-Alarcón, Ó, Lander, O., McDonald, J., Cox, M., Walter, J., Oh, P. L., Ruiz, J. F., Rodriguez, S., Shen, N., Song, S. J., . . . Dominguez-Bello, M. G. The microbiome of uncontacted Amerindians. Science Advances.

Cohan, M. (2017). From ancient tribes to modern civilization, what do our microbiomes say about us? CNN

Conteville, L. C., Oliveira-Ferreira, J., & Vicente, A. C. P. (2019). Gut Microbiome Biomarkers and Functional Diversity Within an Amazonian Semi-Nomadic Hunter–Gatherer Group. Frontiers in Microbiology.

Bengmark, Stig. (2017). Inflammation: From Molecular and Cellular Mechanisms to the Clinic, First Edition. John Wiley & Sons, Ltd.

Survival International. (2019). The Yanomami. 

Some indigenous people from the Amazon have the richest and most diverse microbiota ever recorded in humans. (2015). Gut Microbiota for Health.

Vad är processad mat och hur påverkar den hälsan? (2022). Stig Bengmark.

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