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In Search of the Perfect Gut Microbiome with a Tribe of Tanzanian Hunter-Gatherers

Jeff Leach is taking extreme measures to see how different lifestyles affect gut bacteria.
February 12, 2014, 5:50pm
Image: Human Food Project

It might sound strange to say that humans have forgotten what human-food is, but many scientists believe this is the case. For thousands of years, the environment in which humans lived evolved at a glacial pace—our nutrition and culture changed slowly, and our bodies adapted to it at a matching tempo. More recently, however, our “habitats” have seen massive leaps in technological advancement, and our bodies have not been able to adapt fast enough to these changes, which risks our microbial systems falling out of sync.

Things like packaged long-life foods, super-sanitised water supplies, breast feeding being replaced by powdered formula milk, and an increase in C-section births have meant that the microbes living in and on our bodies are perhaps not as well adjusted to the world we live in. Jeff Leach, founder of the Human Food Project, believes that lots of our modern-world diseases point to a discordance with the ancient microbial world. He explains that “the biological reality that we are vessels to a vast microbial ecosystem is radically altering our basic understanding of medicine, nutrition, public health and the scientific foundation of what makes us sick.”


Leach already investigated the effects of different diets on his microbiome—a collective term for the community of microorganisms that lives in your body—throughout 2013 by mapping his Bacteroidetes and Firmicutes levels (the two main bacterial phyla in the human gut) whilst changing the amounts of meat and fibre he ate. In 2014, he aims to bring his research to new and interesting heights with some really drastic research methods. The aim: to find the healthiest gut microbiome.

Throughout this year, Leach will undertake some radical diet and lifestyle changes to really knock his microbiome off kilter. He plans to explore the impact on his body of drinking binges and smoking copious amounts of weed, all while following certain diets. He will go on a raw food diet, a juicing diet, a vegan diet, an Atkins-type diet, a Mediterranean diet, a Paleo diet, Jenny Craig and Weight Watchers diets … the list goes on, like a conversation you might hear if you hang around Whole Foods long enough.

Leach checking out the local water. Image: Jeff Leach

The most interesting part of the research, however, is the “hunter-gatherer” lifestyle that Leach will take on at one point. In this stage of the project, he's traveling to Tanzania to spend time with the Hadza people, an ethnic community whose hunter-gatherer lifestyle means they have a completely different microbial composition to the western man. The Hadza (also known as Hadzabe) are all naturally born and breastfed for at least two years; they live outside most of the time, are covered in microbial-rich soil, and never use western medications. As you can imagine, Leach expects his own microbial composition to be dramatically altered by sharing their environment for a while.

I contacted Leach to find out more, and caught him while he was at one of the Hadza tribal camps.


Motherboard: Hey Jeff, how are you? I understand you’re communicating via satellite dish?

Jeff Leach: Doing well, thanks. Yeah. I needed to have a way to communicate with the world and keep up with things while conducting research with the Hadzabe hunter-gatherers, but they live in a very remote area of Tanzania.

Where are you right now?

At the moment, I'm hunkered down under a large safari-like tent up on a hill, overlooking Lake Eyasi in the distance. Two of the Hadzabe bush camps we’re studying are within two or three kilometres of where I am.

How long are you going to be there for?

I spent a few months here over the summer, but this time around about a month. But I’ll be back again in June for a three-month stint and then again at the end of the year.

Have you conducted any research there before?

Just this past summer. My previous work in Africa was in Botswana, South Africa, and Namibia.

Hazda huts in Tanzania. Image: Jeff Leach

What’s your daily routine there like?

Daily routine varies. But in short, the sun comes up around 6:30 so we’re up by 5:30. After a bit of stumbling around in the dark we head off in the land cruiser to one of the camps we are working with. Sorry, “we” is myself and my two field assistants: Aziz, who is a six foot six Tanzanian—handy!—and the other is Mariamu, a translator who speaks English, Swahili, and Hadzane.

We usually spend a few hours in the morning at one of the two camps we are working with, collecting poo samples in little cryo tubes, which are then dropped in liquid nitrogen and frozen at -80 degrees Celcius. We spend a lot of time monitoring what the Hadzabe eat. I go out on hunting trips, honey-collecting parties, and out to dig roots with women, etcetera. Usually it’s too hot by mid-afternoon to do anything. The Hadzabe slow down and chill as well—everyone waits for early evening to go hunting. We usually head back to our camp and catch up on things.


Is it difficult to adapt to Hadza tribal life from a western lifestyle? Are you noticing any physical changes in your body?

When I was here in August to October it was the late dry season so we had lots of meat—zebra, kudu, bush pig, impala, etcetera. Now it's the wet season and animals are more dispersed so they’re harder to kill. Not much meat has been eaten in the last two weeks between the two camps (there are about 10-15 people in each camp). So I've been pretty much on a vegetarian diet this go around, dominated by wild honey—we eat the honey, larvae, and a lot of wax. [I’ve also been] eating lots of baobab fruit, roots, berries.

In short, fibre intake hovers between 100-300 grams per day. Other than getting really tan, my dirt-covered frame has probably been reduced by a few kilos. The high fibre diet results in three to four bush/bathroom visits a day. I also probably drink five kilograms of water a day from the same sources as the Hadza use—little catchments and springs.

Can you tell me a little about the Human Food Project?

The HFP is an effort to blur the boundary between the science and people’s understanding of that science. It's a vehicle to have a conversation with people about the exciting science of genomics that's changing our understanding of how we define the self. It used to just be us, but now that we know 90 percent of the cells in the human body are not even human—they are microbial—then we really need to pay attention to how diet and lifestyle impacts them as well. Basically, we need diet and lifestyle strategies that address us and them. Current strategies only address ten percent of the equation.

Leach with a local child. Image: Jeff Leach

What inspired you to become so interested in the way a western diet can affect our microbes?

I became interested in the impact of diet and lifestyle on the gut microbiome when my then-two-year-old daughter was diagnosed with type one diabetes, which is an autoimmune disease. Once I started looking into the science it was clear that she was in too clean of a world. It was also clear not many people were working in rural populations, much less hunter-gatherer societies. This piece was missing and that’s why I'm in Africa.


What health differences can you notice between the Hadza people and the average American or British citizen?

Our project with the Hadza is not to diagnose disease. We collect poo, swab plants and animals for microbes, and document diet and lifestyle habitats during the sampling periods. That said, the Hadza don't suffer from obesity, nor diabetes for that matter. As for other diseases, they do take their toll on the young—things like TB and malaria.

What are you hoping to find?

Good question. Everyone in the western world is wondering what gut microbes they should have and spend a lot of time taking probiotics and eating fermented foods, all for the microbes. The holy grail would be to determine what an optimal gut flora looks like, i.e. what researchers and consumers are looking for in the west. However, I don't think there is one optimal microbiome. The Hadza follow a seasonal diet that shifts dramatically between the wet and dry seasons. For example, in the dry season the Hadza eat tons of meat as there are limited water sources and the game is more predictable.

The holy grail would be to determine what an optimal gut flora looks like, i.e. what researchers and consumers are looking for in the west

It’s the opposite in the wet season; game is scattered, and harder to kill. I'm here in the wet season now. There’s not much meat, but lots of wild honey and larvae and pollen, lots of berries, baobab fruit, and roots. We suspect the gut microbiota of the Hadza shifts as the diet changes. If that’s true then the optimal human microbiome is a moving target, in a constant state of flux. We also suspect the Hadza will harbour a greater diversity of gut bugs—which, as Ecology 101 teaches us, is protective.

With your results, what are the possible applications?


Educate the masses.

I know that for a part of your research you have been trying lots of different diet styles. Which was the best? 

Yup. Too funny. Throughout 2014 I will go on six to ten different diets, and I’m collecting my poo along the way to monitor the impact on my gut flora. Hands down, I'm a meat eater with lots and lots of veggies, don't like grains that much. So the Hadza diet I just went on for the last 10 days, eating snails, berries, wild honey, some meat, baobab, etcetera was awesome. Maybe because I foraged all those foods myself, or the environment of East Africa where the Hadza live, but I've never felt so alive.

Awesome. Which was the worst?

I’ve not done it yet but I'm pretty sure the raw food diet is going to suck—mainly for me, not sure for my gut bugs yet. A close second on the worst scale will probably be the low-to-no carb diet.  I bet that’s going to do a number on my gut bugs.

I saw that for one part of your research you were going to be exploring the impact of smoking quite a bit of weed, waking’n’baking whilst holding various diets constant. Why’s that? What do you think you’ll find there?

Not sure what I will find, if anything. As for why, I don't require much prodding to partake on a regular basis. Though this will be some heavy duty smoking—all in the name of science.

Amazing. Thanks so much for talking to us, Jeff. What’s next for you today? 

Packing up camp in the next few days and heading back to civilisation. Think I will spend a few days kite surfing in Zanzibar. And do a little fine dining on some food someone else hunted and gathered just for me.