Published on 26th March 2017


The human microbiome is under the microscope, but anthropologist Jeff Leach is joining up the dots between our depleted gut microbes and a depleted wider environment, writes Louise Wates

As science continues to reveal how the billions of bacteria that live in and on us contribute to our health, there have been many column inches (several in this magazine) dedicated to looking at how diet can boost their diversity within the gut microbiome.

But Jeff Leach, anthropologist, co-founder of the American Gut Project, visiting research fellow at the Department of Twin Research and Genetic Epidemiology at King’s College London (KCL), writer, and all-round rather interesting chap, is one of several academics who is looking beyond what we eat and asking how much the depleted western microbiome is simply a mirror of a depleted wider environment.

First, let me say that I would be a liar if I said that it was this aspect of Leach’s work that caught my attention.

It was certainly something scientific, but also rather eye-watering.

Speaking last year on Radio 4’s Food Programme, Leach described how while observing the Hadza, a hunter-gatherer group in East Africa, he had carried out what a scientist friend of mine gleefully calls a “transpoosion”; in other words, a Faecal Microbiota Transplant (FMT), in which a sample of faeces is taken from a donor and transplanted to a recipient so that the latter can benefit from the donor’s healthier microbiome. It sounds pretty grim, but this is real science; so much so that mice in laboratories around the world are having their poo studied and shared to see if a donation from a different mouse will make them fatter, thinner, healthier or unhealthier. In humans, FMT is also currently 

used as a proven treatment for Clostridium difficile (C.diff) infections. Leach, however, wasn’t sick. And rather than doing this in a well-equipped clinic, he used a turkey baster. Medical checks were carried out and permission obtained first, but let’s just say: don’t try it at home. If you want more details (and you probably do) then read his book Rewild.

It’s not unusual for scientists to experiment on themselves. Barry Marshall drinking cultures from a Petri dish led to the discovery that Helicobacter pylori (H. pylori) causes ulcers. And these days, doctor-presenters are frequently turned into subjects in the name of good science and even better TV.

In Rewild, a collection of essays looking at and musing on the microbiome, Leach wrote that faecal transplants are set to “become the new black”. But he wanted to try it to see if a rich and diverse microbiota obtained from a Hadza donor would be wrecked by his typically western diet and lifestyle. One could ask why he might want to destroy a newly acquired, richer microbiome, but that’s scientists for you. As Leach explains in Rewild, the point was not to gain a more diverse microbiome, it was to see what urbanisation and modernity have done to our guts over time. So the Hadzas’ microbiome would represent our hunter-gatherer ancestors, and Jeff’s would represent modern, western humans. But instead of change taking generations to occur, in Jeff’s gut it would take days. (When asked if he noticed feelings of wellness when his gut was in what might be assumed to be a better bacterial state Jeff says only: “Good Q. Don’t know.”)

Leach’s deep curiosity about the microbiome was partly fuelled when his daughter was diagnosed with the autoimmune condition type 1 diabetes. Although the condition has a genetic element, Leach wondered whether her caesarean birth had affected her microbiome, as studies have shown that babies born this way do not benefit from the transition of bacteria from the birth canal. He told Optimum Nutrition that he’d had the realisation that not just diet but other lifestyle choices could modulate the gut microbiota.

The Hadza, however, Leach has observed, get as close to their environment and diverse microbes as it is possible to be. When an animal is killed, the hunters’ hands go right into the very guts as the meat is cut and prepared, with titbits of colon and stomach eaten as they go along — the only ‘cleaning’ involved being removal of the animal’s faeces.
In lifestyle, the Hadza are possibly as close as any humans can be to our hunter-gatherer ancestors. The rest of us, however, are now far removed from the environment and lifestyle that would have shaped our ancestors’ microbiomes. In Leach’s view, this is having a negative impact on the diversity of the microbiome.

Are we too clean? “Sure,” he says. “I think we might be too clean.

“However, culturally that isn’t going to change. We are only going to get cleaner,” he says. “The bigger issue, in my opinion, is the fact that 50 per cent of the world’s population lives in urban settings — and that number will grow.”

Urban settings, he explains, mean being exposed to fewer plants and fewer animals which, in turn, means exposure to fewer microbes. Recently, he wrote people who faithfully fill out their ‘daily activity’ and ‘food diary’ logs on fitness websites. “Unlike most people who join these sites and fill out the info from time-to-time to track things like calories, there are a tiny, tiny percentage of these participants who provide extraordinary detail about their daily lives,” he says. “If you could tap into this — and I believe there are thousands of these people — I think you might be able to extend the importance of tightly controlled and sequestered cohorts — which are typically small and expensive — to a larger, free-living cohort.

“The key is numbers. I believe efforts like American Gut and MapMyGut are tapping into this now, but with less than ideal metadata.”

If we are to think about a healthy microbiome, however, he believes we should be thinking far beyond what we eat. “I don’t think diet, per se, is what we should be focusing on,” he says. Diet, antibiotics, hyper-hygiene practices etc., he says, are “just filters” that prevent contact with microbes. “This is striking when you consider the developed world against the backdrop of our work in Africa.”

“The hunters’ hands go right into the very guts as the meat is cut and prepared, with titbits of colon and stomach eaten as they go along — the only ‘cleaning’ involved being removal of the animal’s faeces”

To illustrate the point he emails me a diagram showing exposure to the environment in the developed world vs. the Hadza world. While the Hadza are exposed to a variety of flora and fauna, the developed world looks remarkably barren, with most exposure to animals being just a few household pets. Then while the Hadza have very few filters between them and diverse microbes, we have antibiotics, pesticides, little or no breastfeeding and clean, sterile food preparation for ‘protection’. So while old friends (and enemies) may not be getting through, we might be exposed to new ones because we have manipulated the environment and changed what we are exposed to.

So it is possibly unsurprising that in Rewild, Leach is pictured drinking from a water hole that is shared by Hadza, birds and baboons. “I’m not scared of food with a little dirt on it,” he says. American Gut and other research has also impacted the way that he eats: he doesn’t completely avoid processed foods, but doesn’t seek them out, either. His biggest focus, he says, is ensuring he eats a lot of dietary fibre from a number of sources. “I go out of my way to eat foods with fructans such as leeks, onions, garlic etc., — prebiotics if you will.” And if we were looking for advice, we could refer back to Rewild where he recommends we open our windows and get our hands dirty.

But after years of trying to keep the natural world out, is it a challenge to which we can rise?

Rewild: You’re 99% Microbe. It’s Time You Started Eating Like It
Jeff D Leach | ISBN 9781515355410

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