“I have 15 cows, how many do you have?” Chief Jambiru asked me.
“How many cows do I have?” I thought. What an odd question. But I shouldn’t have that so, as I had just asked the Chief how many cows he owned.
Turning my bovine query back on me caught me a little off guard and it took me a moment to realize he was not poking fun at me, but seriously wanted know how many cows I owned.
“None at the moment,” I said.
So there we sat, in a dry, sandy creek bed high in the rugged mountains of northern Namibia near the Angola border, me cross-legged on one side of the crackling fire and the Chief in a deep squat perched effortlessly on a fist-sized stone on the other side, both thinking to ourselves how curious the other was. How could I not have any cows!
I was only the second white man the Chief had ever seen, according to our translator Ziggie. A few years back, the Chief had crossed paths with another white guy hiking in the mountains in search of what I gathered was exotic Aloe Vera plants. Though the translation was a little sketchy. I guess I shouldn’t have been surprised when Ziggie verified that a female colleague in our group was the first white woman the Chief had ever laid eyes on.
To be fair, the Chief and his three friends who also squatted effortlessly onto frighteningly small stones in the sand around the fire, along with the twenty or so other men, women and children in his dry-season camp located only a stones throw from our camp fire, were the first mountain Otjhimba I had ever met. It was a number of firsts all around.
As the evening went on and the Southern Cross appeared in the night sky, and the smell and sound of fresh meat – a gift from the Chief – sizzling atop hot rocks on the edge of the fire filled the cool night air, I began to wonder if we had found the people I had traveled 8,000 miles to the bottom of the world to find. Were these the Honey People of the mountains of northern Namibia – one of the last true remaining hunter-gatherer groups in all of southern Africa? The presence of cows, no matter how scrawny – and the distinctive “maaa” of goats in the distance – suggested no. True hunter-gatherers do not keep livestock.
Had globalization finally caught up with the Honey People, was I a few years too late, or were we in the wrong dry creek bed, on the wrong mountain, sharing meat with the wrong, though stunningly gracious, people?
I started to do the math. If I was only the second white man and the first was the Aloe Vera hunter, then these could not be the Honey People as I had learned of their whereabouts from a white South African who had spent several days with them back in 2006. That meant I should have been the third white man. Surely the Chief would have remembered white man number one.
My trek to the hills of northern Namibia and the meeting with the Chief took place this past summer. I was there because despite piles of peer-reviewed research and major research efforts such as the NIH’s massive Human Microbiome Project and similarly large efforts in Europe, we still do not have a good handle on what a ‘normal’ or ‘healthy’ gut microbiome looks like. And we may never know. It may be that our modern world of processed foods, antibiotics, fancy indoor plumbing and a wet wipe at every turn, may have forever altered our ancient gut inhabitants. (Remember your gut microbiome is all the microbes in your gut and their genes).
I thought about the Chief and why I had gone to Africa the other day while leaning against my shopping cart at our local grocery store – trying to decide what I should eat that night. More specifically, what should I feed my gut bugs. I spent a lot of time over the last few years pouring over every microbiome-related study showing how diet (and lifestyle) shift the composition of our gut microbiome. We know that most of us have more or less hundreds (if not a lot more) species of bacteria in our gut – some are permanent members who numbers go up and down and others are more transient (just passing through as they say).
There are countless studies showing that if you feed humans or mice either a low fat, high fiber, or All-American westernized diet, the composition of the bacteria shifts (some species/genus/phyla go up in number, some go down). These experiments reveal that you can start with one diet, check the composition of the bacteria using DNA techniques, then change the diet for a period of time, measure again, and then shift the diet back to the original (baseline), then analyze the bacteria at the end. Throughout this roller coaster of diet shifts (sound familiar?), the bacterial communities shift as well – depending on the study, the shifts occur at higher phylogenic levels (like shifts in the phyla Firmicutes and Bacteroidetes), but in some studies shifts at lower genus and species levels are apparent.
In either case, we can say with some level of certainty that dietary inputs shape the composition of our gut microbial community. But should we be worried that our gut microbial communities shift around as a function of what we eat and if so, which composition (or ‘state’ as the ecologists like to say), should we be aiming for? That is the million-dollar question.
We know that someone who takes antibiotics can dramatically shift their gut microbes. When this happens, the diversity of the gut microbial ‘ecosystem’ also declines. When diversity declines – among other things – the individual is susceptible to secondary infection. The most talked about secondary infection is by Clostridium difficile, or C. Diff for short. The scorched earth outcome of many broad-spectrum antibiotics is analogous to spraying poison all over your backyard plants and grass and waiting to see what grows back. In the case of your gut ecosystem – just like in your yard – invasive and maybe some not-so-good species (microbes in the case of your gut and some funky weeds in your yard) carve out a niche in the available gut/yard landscape.
From this perspective – gut microbial communities as ecosystems – the ecological principles of diversity and resilience start to help you think about how to fortify your gut against not only invaders that seek to do you harm (also think about E. Coli and others), but also about nurturing a diverse community within your gut that provides what ecologists call ‘ecosystem services.’ In the case of your gut bugs, the services they provide include harvesting energy from otherwise useless nutrients like dietary fiber, pathogen resistance through a number of mechanisms, synthesizing vitamins, assisting in the maintenance of the mucosal barrier that lines in the inside of your intestinal tract – which helps regulate immune response and reduce leaky gut – and the list goes on. In short, when your gut ecosystem shifts as a result of a perturbation – like an insult from an antibiotic, drug, or a shift in your diet maybe – then your equilibrium is out of balance and you tip towards an unstable state which may open you up to disease.
Some interesting studies in mice and humans have shown that a high fat diet can shift your gut microbes which in turn has the knock on effect of low-grade inflammation as measured by circulating levels (in your blood) of a plasma endotoxin known as lipopolysaccharide (LPS). LPS is the primary structural component of the outer membrane of Gram-negative bacteria found in the gut. So how can shifting your gut microbes cause an increase of LPS in your blood? Turns out, the high fat diet reduces (shifts) the levels of Bifidobacterium. These particular bacteria are known to produce short-chain fatty acids (butyrate, propionate and lactate) as a byproduct of fermenting things like dietary fiber. When their numbers go down – as with a high fat diet – the amount of short-chain fatty acids (SCFA) go down as well. These SCFAs are known to improve gut barrier function (think leaky gut) through a number of mechanisms.
So, in this ‘one example,’ if you change your diet (higher fat in this case) you reduce your SCFA production – which is an ecosystem service provided by your microbes – then your gut starts to leak and things that do not belong in your blood start showing up (LPS) and cause low-grade inflammation (the lab coats call it endotoxemia) which has been linked to insulin resistance, type 2 diabetes and obesity (click here for longer discussion on this). It’s interesting to note, that its not the fat per se that causes the Bifidobacterium to shift downward in abundance and thus cause a leaky gut, but the reduction of fermentable substrates. That’s is, you cut off the Bifido’s food supply and thus they slow down the SCFA production – which is prtective. As the famous Rajin Cajun James Carville might say, “It’s the Fiber stupid.”
So what should you eat to improve the diversity and possible resilience of your gut microbiome to reduce the risk to invading pathogens, unnecessary inflammation, leaky gut and so forth? Nobody really knows for sure and the answer is likely different for different age groups and populations. But at a minimum, you want that ecosystem service of SCFAs to keep churning along at high levels – so eat as many plants a week as you can (30-50 is a good number to shoot for – keep track and see how you do) – that is, keep the fiber (non-starch polysacchrides, resistant starch etc) flowing to your colon. And maybe cut back a bit on the easy to digest and hyper-cooked and processed foods – letting your stomach do a little extra-somatic work every now and then. Maybe even open a window every now and then, and for god’s sake, get your hands and food a little dirty. But if we ever hope to get a better handle on what a ‘normal’ or ‘healthy’ gut (or skin, oral etc for that matter) microbiome looks like, we will need to look at less westernized populations who are still undergoing the epidemiological transitions most of us have already undergone.
Getting a larger sample of westernized gut microbiomes is necessary as well and the reason we launched the American Gut project – to crowd source 10,000 gut microbiomes across the diversity that is the American Gut. And also the reason I was trekking in the mountains of northern Namibia. With detailed dietary and lifestyle data and the resulting microbiomes from the American Gut project, we will be able to see patterns not otherwise possible in smaller groups of people. By comparing this data set to more traditional societies – the microbial Noah’s Arks I like to think of them as – we might get a glimpse of how the process of village to urban life shifted and altered our ancient gut microbiome to its current – and very possibly –persistently perturbed state.
I will be headed back to that mountaintop in the next few months to see the Chief again, and explore a few new valleys and ridge tops in the hopes of locating these ghosts of our ancestral past. And hopefully they will agree to help.