Christmas dinner is over, and perhaps you’ve retired to the couch, seized by a wave of post-turkey drowsiness. But as your brain relaxes into a contented stupor, your sated gut is just gearing up for a master performance, involving a cast of trillions.
Long considered a biological backwater, the humble gut is finally getting some serious attention. Home to a vast and motley collection of tiny single-celled creatures known as microbes, the gut is at the centre of a scientific revolution that is changing the way we think about ourselves and our place in the world.
As researchers have discovered, we are not alone. “Even within our own bodies, we’re drowned out by a chorus of independent (and interdependent) life-forms with their own goals and agendas,” writes microbiologist Rob Knight in Follow Your Gut: The Enormous Impact of Tiny Microbes, one of a growing number of recent books about our bustling internal communities. Like all major scientific advances, mapping this invisible world has implications far beyond the laboratory: the sheer number of our resident microbes — about 100 trillion — forces us to radically expand our definition of “self.” To quote Knight, “We are not individuals; we are ecosystems.” And if we want to thrive, we have to learn to take care of our microbes, just as they take care of us.
Based on a lecture Knight gave for the popular TED Talks series, Follow Your Gut is a fascinating primer on the paradigm-shifting potential of microecology. For every human cell in our body, Knight tells us, there are 10 microbial ones, the great bulk of which can be found in our gut. What are these occupiers doing down there? Quite a lot, it turns out. They help us extract energy from food and train our immune system to distinguish friendly bacteria from hostile invaders. More profoundly, new research shows that our microbial populations affect our weight, our moods and even our personality. They may also hold the key to diseases such as arthritis, multiple sclerosis, autism and depression. The science is still in its early stages, the book cautions, but “the glimmers of future treatments” are there. In time, we might be able to remedy a host of ailments by repairing our inner biome.
An enchanting guide to this emerging world is Giulia Enders, a medical student whose book on the marvellous mechanics of the gut became a surprise bestseller in its native Germany. Released last spring in Canada, Gut: The Inside Story of Our Body’s Most Underrated Organ offers an enthusiastic tour through the twists and turns of our digestive system. Whimsical drawings by her sister add to the book’s charm.
Enders takes an unabashed delight in the complexity of our least glamorous bodily functions, conjuring up, for example, the anxious internal monologue of our external sphincter muscle (“It might, theoretically, be possible to use this stranger’s toilet, but is that a good idea?”).
She also paints a colourful picture of our microbial landscapes, from the “breezy meadow” of our forehead to the “arid wastelands” of our elbows. The gut, she writes, is a “giant forest . . . populated by the weirdest of creatures.”
When it comes to the outsize influence of these tiny characters, Enders speaks from personal experience: it was a health issue that first sparked her interest in the gut. Afflicted by a mysterious skin disease as a teen, she plunged into research, eventually concluding that the source of the problem lay in her intestinal flora. She changed her diet and subjected herself to a variety of experiments (accidentally overdosing on zinc in the process) before finally getting her condition under control.
Enders speculates that her caesarean entrance into the world and lack of breastfeeding may have left her with an impoverished collection of microbes. Antibiotics, too, while unquestionably lifesavers, tend to wipe out the good bacteria along with the bad.
Indeed, at the same time as scientists are discovering the wonders of our microbial universe, they’re also realizing that the modern human gut is only a shadow of its former self. While our ancestors roamed through the bush and dug in the soil, immersing themselves in a rich variety of microbial life, we’ve swapped foraged meals for French fries served up in sterile buildings. Just as habitat destruction and industrial agriculture have reduced biodiversity in the natural world, our internal ecosystems now host a shrinking assortment of species. Writing in the New York Times in 2013, author Michael Pollan describes the western microbiome as “an artifact of civilization, no more a wilderness today than, say, the New Jersey Meadowlands.”
Unfortunately, this greater microbial conformity seems to be playing havoc with our immune systems. With fewer true villains to pounce on, our restless immune cells may instead target peanuts, wheat or even human tissue, contributing to the modern spike in allergies and autoimmune diseases.
So how do we restore the lost Edens of our guts? While microbiologists tend to stress that more research is needed, their findings have already spawned a flourishing side industry of diet books and probiotic supplements (beneficial bacteria in capsule form). The solution is no doubt more complicated than “take 20 million colonies of L. acidophilus and call me in the morning.” But as the science emerges, there are simple things we can do in the meantime to make our microbiomes more robust. Spend more time in nature. Pet a dog and wait a bit before washing our hands. Eat fewer processed foods and more fibre. This last one is especially important, as the roughage in certain vegetables and grains, indigestible by human enzymes, nurtures a group of friendly bacteria that help to crowd out troublemakers in the gut. “Good bacteria do us good,” Enders writes. “We should feed them well so they can populate as much of our large intestine as possible.”
And as we tend to our internal gardens, we might also set about restoring our external ecosystems, since the health of the two go hand in hand. As our microbial companions teach us, being human means being in relationship, with creatures both great and small.
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