The next time you’re out on the street, take a look at the people around you: The suit-wearing, busy office worker on his way to work, the female shopper carrying huge bags of newly bought clothes, the homeless guy living on the street corner, and the athlete on his way back from the gym. These people may all look and seem very different; however, they also have some things in common, one of which being that they all most likely suffer from some type of evolutionary mismatch disorder, whether it’s myopia, lower crossed syndrome, acne vulgaris, asthma, or more serious conditions such as type-2 diabetes or cardiovascular disease.
These and other so-called diseases of civilization, which were rare or nonexistent among our hunter-gatherer forebears, are highly prevalent in contemporary, industrialized societies. This doesn’t really come as a surprise when we consider the fact that we now live in a milieu that is completely different from the ancestral environments for which most of our genes were selected.
We’ve known for a long time that a western lifestyle adversely affects the expression of the human genes we carry with us throughout life. What we’re now learning is that the impact on the second genome in our body – the human microbiome – may in some ways be even more severe.
When researchers first set out to map the microorganisms that live in and on the human body about a decade ago, they focused their attention on modern, industrialized people. The comprehensive research efforts that followed over the proceeding years gave us invaluable knowledge about our microbial inhabitants and their relationship with the human host. However, this initial approach to microbiome science also had its limitations, one of which being that it’s difficult – if not impossible – to establish what a healthy human microbiota may look like by studying industrialized populations.
In the western world, we’ve all been compromised in some way. Among other things, we drink chlorinated water, take antibiotics, eat processed food, and give babies infant formula that lacks the complex mix of microbes and prebiotics that are found in real breast milk. Over generations – as the damage has accumulated and microbes have been passed on from mothers to offsprings – there have been marked changes to our microbiomes.
In other words, to be able to establish what a complete, “unadulterated” human microbiome may look like, we have to turn our attention away from our own homelands and towards non-westernized, traditional societies. This fact hasn’t been missed by the scientific community, and over the last several years, studies with the purpose of mapping “the non-westernized microbiome” have been carried out among traditional populations such as the Hadza, a group of hunter-gatherers in Tanzania, Africa; the Tunapuco, a traditional agricultural community from the Andean highland; and the BaAka, a group of rainforest hunter-gatherers (1, 2, 3, 4).
One of the most important takeaways from these studies is that individuals who lead traditional lifestyles house a much greater diversity of microbes than westerners, including species that are never found in the guts of modern, industrialized people.
Examinations of ancient coprolites and analyses of the microbiomes of many different primate species further support the idea that human microbiomes have deviated from the ancestral state at an accelerated rate (5, 6). Here’s what a 2012 paper had to say about the matter:
Overall these studies reveal that human microbiome data has been preserved in some coprolites, and these preserved human microbiomes match more closely to those from the rural communities than to those from cosmopolitan communities. These results suggest that the modern cosmopolitan lifestyle resulted in a dramatic change to the human gut microbiome. (5)
Since we live in an environment that is very different from the ones hunter-gatherers occupy, we’re not necessarily best off harbouring the same mix of microbes as they do. As I’ve pointed out many times on the blog, the microbiota can adapt rapidly to environmental changes, meaning that what constitutes a well-functioning microbiome must be viewed in light of what kind of diet and lifestyle the human host adheres to. That said, there’s no doubt in my mind that we can learn a lot about how to shape a healthy microbiome by studying indigenous, non-westernized people.
Our modern way of life is putting the man-microbe relationship to the ultimate test
A modern lifestyle – with its chronic inactivity, processed foods, antibiotics, c-sections, and antibacterial lotions – is putting the man-microbe relationship that was forged over eons of time to the ultimate test. By designing and moving into closed buildings, adopting evolutionarily novel lifestyle habits, spraying our crops with man-made pesticides, and distancing ourselves from nature we’ve unknowingly disrupted the microbial ecosystems that not only live around us, but also in and on us.
The human body is not adapted to harbour the type of microbiome you get from eating highly processed food, taking broad-spectrum antibiotics, and living in closed-off, poorly ventilated buildings. In other words, the modern lifestyle selects for a microbiome that is mismatched with the human genome.
There’s little doubt that gut dysbiosis, which is defined as an unhealthy change in the normal bacterial ecology of the gut, is now an epidemic. Irritable bowel syndrome, insulin resistance, the metabolic syndrome, gallstones, type-2 diabetes, food intolerance, inflammatory bowel disease, and chronic depression are just some of the numerous health conditions that we now know are associated with a microbial imbalance in the gut (7, 8, 9, 10, 11). More readily apparent signs and symptoms of dysbiosis – whether it be in the oral cavity, gut, or any other location on the human body – include things like poor breath, a white coating on the tongue, obesity, and acne vulgaris.
Recent research has made it clear that gut dysbiosis and other disorders of the microbiome aren’t just benign conditions that occur secondary to chronic disease, but rather important underlying factors that are driving the development and progression of some health disorders (7, 11, 12). Here’s what a recent review paper had to say about the role of biome depletion in modern diseases associated with abnormal immune responses:
Evolutionary mismatches have left the typical immune system of industrialized humans prone to a wide range of allergic, autoimmune and inflammatory disease.
The primary factor associated with allergic and autoimmune disease is apparently loss of species diversity from the ecosystem of the human body, the human biome. Species depleted or even eliminated from the human biome include a wide range of pathogens, commensals and mutualists whose reproductive cycle is greatly diminished or even eliminated by modern sanitation, water treatment and medical practices. Importantly, the human biome, as with other biomes, not only includes species that are permanent residents of the ecosystem but also species that interact transiently with the ecosystem. The absence of species from the human biome leaves the immune system in a hypersensitive state that, when combined with environmental triggers and genetic predisposition, leads to allergic and autoimmune disease. (12)
The human superorganism
The human body is best viewed as a superorganism that is composed of trillions of microorganisms that co-exist side-by-side with the human host. We’re not separated from the environment around us; we are a part of it – connected to everything else through our invisible microbial inhabitants.
The air we breathe, the soil we touch, the plants we eat, and the family dog we take for a walk every morning all have their own microbiota, which interact with the one we carry with us. When we design homes and office buildings that are poorly ventilated and susceptible to mold growth, disrupt the microbial ecosystems in the soil with pesticides, or give the family dog cheap, nutrient-poor dog food from the grocery store, we’re messing with the balance of microbes in the environment that surrounds us, something that can have ripple effects down to the microbial reactor found in the tube that runs through our own body.
The microbes that call our body home regulate our intestinal barrier function, control our immune system, and produce a wide-range of enzymes, hormones, and neurotransmitters that play a role in our digestion, metabolism, and brain chemistry. When we put together what we know about the impact our lifestyle has on the microbiome and the role microbes play in shaping our health, it shouldn’t really come as a surprise that diseases associated with perturbations of the microbiota are now a huge problem in our modern society.
A dysfunctional microbiome can negatively impact our health through several different pathways, with perhaps the most well-known being that a microbial imbalance in the gut leads to increased translocation of bacterial endotoxins (“leaky gut”), activation of toll-like receptor 4, and chronic low-grade inflammation. It’s this inflammatory tone that’s problematic, as there are solid data to show that inflammation is at the root of many, if not most, of the chronic health disorders that plague us in contemporary societies.
The hidden epidemic
Microbial dysbiosis and other disorders of the microbiome are – or at least have been – hidden epidemics in the sense that we can’t see the trillions of critters that inhabit our body with the naked eye. It’s only very recently that scientists started mapping the human microbiome and we began to understand how complex the microbial rainforest that is found in our gut really is.
A mere 5-7 years ago, gut dysbiosis and leaky gut were considered by many to be “bogus diagnoses”, and health practitioners and scientists who claimed that microbial imbalances and candida overgrowth could lead to health problems such as irritable bowel syndrome, colon cancer, and autism were often ridiculed or labeled as quacks.
In the years that have passed, things have certainly changed a lot. No one who has bothered to keep up with the news coverage on gut bacteria or done a quick search for “microbiome” at PubMed doubts that gut dysbiosis is a real problem that afflicts millions of people worldwide.
Unfortunately, most people out there still know very little about the microbes they carry with them throughout life – and much less about the microbial environment around them. They may be completely unaware of the fact that their lifestyle has a profound impact on the composition of their microbiota or that their nagging headache, constant sugar cravings, disturbed sleep, and digestive issues are directly linked to a microbial imbalance deep down in their gut.
A lot of people have spent thousands of dollars on visits to various doctors and health practitioners and tried numerous diets, supplements, and drugs in order to overcome their health issues, but their health complaints remain as pervasive as ever. A large part of the problem is that the human microbiome hasn’t fully made its way from scientific journals into the offices of general health practitioners or the curriculum of medical schools.
Manipulation of the microbiome: The future of medicine?
Diet and lifestyle changes, and in some cases, remediation of poor indoor air quality, play a key role in repairing a dysfunctional microbiota. Unfortunately, most doctors know very little about nutrition, ancestral health, indoor mold toxicity, and the sick building syndrome, and they therefore have scant good advice to offer patients who suffer from health problems that are associated with a degraded, poorly functioning microbiota. Some medical professionals even believe that diet and microbial exposure have little, if any, impact on our health, a belief that may have been imprinted in their minds throughout a medical education that neglects the importance of these factors.
Another major issue at the moment is that there are no pills or drugs on the market that are specifically designed to repair a damaged microbiota. Most of the probiotic supplements on the market today only provide limited benefits, and some may even do us more harm than good. Fecal microbiota transplants have been shown to be very effective for some health disorders, but they are restricted by the medical industry, quite invasive, and expensive (at least those performed in a clinic). Not to mention the fact that many patients are grossed out by the whole procedure.
So, where does that leave us? We have to take responsibility for our own health and do the best we can with what we’ve got available to us. A lot of people can resolve their health issues “simply” by adopting a fiber-rich, whole foods diet and an ancestral lifestyle. However, for those with a severely damaged gut microbiota, this may not be sufficient to remedy the problem, meaning that to really be able to overcome – or at least slow down – the current epidemic of damaged gut microbiota, readily available and cheap solutions for repairing a dysfunctional microbiome may be required.
I think the overarching message from all of this is that we should all pay a little more attention to the invisible organisms that live on this planet alongside us. Not just the ones that inhabit our own body, but also the ones that live in our homes, in our soil, and in the guts of our pets; because in the end, it is all connected.