In the past few days I have posted an episode of NPR's Radiolab on Guts and another article on the gut microbes (the microbiome) that may be a powerful driver of evolution. And here, from Somatosphere, is another article on "guts," this one by a man living with Crohn's Disease.
Since Cohen mentions the enteric nervous system, and that 90-95% of the serotonin production in the human body occurs in the gut:
Approximately 90% of the human body's total serotonin is located in the enterochromaffin cells in the alimentary canal (gut), where it is used to regulate intestinal movements.[7][8] The remainder is synthesized in serotonergic neurons of the CNS, where it has various functions. These include the regulation of mood, appetite, and sleep. Serotonin also has some cognitive functions, including memory and learning. Modulation of serotonin at synapses is thought to be a major action of several classes of pharmacological antidepressants.Drugs which block 5-HT2C receptors (several antidepressants) make the body unable to recognize when it is no longer hungry or otherwise in need of nutrients, and are associated with increased weight gain, one of the common side effects of these drugs, as well as the atypical antipsychotics.
If we want to avail ourselves of the natural intelligence of the enteric nervous system (the gut), drugs that affect serotonin are likely to make that more than a little challenging.
Gut Wisdom, Or Why We Are More Intelligent than We Know
By Ed Cohen
Gut feeling. Go with your gut. Gut of the problem. By default I’m a gut guy. At the age of thirteen I was diagnosed with acute Crohn’s Disease. For the next ten years I was borderline incontinent. Then I had a small bowel occlusion that resulted in complications precipitating a near death experience after which several feet of festering small intestine were excised from my viscera. Since then I’ve been living with the guts I have left. Needless to say I’ve had a few opportunities to reflect on “the gut” over the last forty years.
In evolutionary terms, the gut localizes and intensifies a paradox familiar to all living organisms: to live entails being simultaneously open and bounded. Francisco Varela succinctly defined this vital conundrum when he described “the intriguing paradoxicality proper to an autonomous identity: the living system must distinguish itself from its environment, while at the same time maintaining its coupling; this linkage cannot be detached since it is against this very environment from which the organisms arises, comes forth.”[i] In order to maintain this distinctive coupling, the permeable cell membrane has been as continuously conserved through the course of evolution as the crystalline DNA molecule, suggesting that the organism’s lively paradox constitutes an irreducible tension from which the living stretches itself out in time and space. Be that as it may, the gut contains this lively paradox in the most literal way: it folds the outside inward in order to keep the perturbations entailed by that paradox contained. In other words, it helps us hold our shit together. And by incorporating the open/bounded situation of the living, the gut constitutes the paradox that we are. If the gut is the way the outside lives inside of us — which of course in a topological sense it must be — then we are twisted around our guts, rather than our guts being twisted up inside of us, no matter how often we might feel the latter to be the case.
Single celled organisms don’t have guts. Guts evolve in multi-celled beings in order to govern the complex flows of nutrients and toxins that pervade the cellular world. The more convoluted the flows become the more the gut matters. Some argue that the first creatures to develop organized nervous systems were worms. Guts with brains. It’s hard to imagine, then, why people were so surprised when the enteric nervous system, the so-called “brain-in-the-gut,” was “discovered” at the end of the twentieth century. Yet, until then, for as long as anatomists had been dissecting human viscera they managed to miss this possibility. Oops. And how did the enteric nervous system finally come to our attention? Psycho-pharmacologists began prescribing SSRIs to people with depression and they noticed that one of the side effects was constipation. But why should a drug that helps us hold our shit together literally hold our shit together? It turns out the gut has all the same neuro-receptors and makes all the same neuro-transmitters as the brain does (and more recently the same has been found to be the case for the heart). Indeed the gut makes 95% of all the serotonin in the human body.[ii] So now bioscience finally acknowledges what non-scientists have been saying for quite some time: the gut has a mind of its own. Quelle surprise. After all, what does “gut wisdom” mean besides this? Seems like now that we are finally giving the gut its due, we’re finding out that we are more intelligent than we ever knew.
Perhaps the motto of gut wisdom, then, ought to be: We are more than we know, for when it comes from the gut, intelligence does not take the form of knowledge. When Kant proposed his motto for the Enlightenment: Sapere Aude—Dare to Know, he ensconced a precept that privileged knowing over not-knowing as a properly human goal, the path to “maturity” as he would have it. In the two centuries since, this precept garnered the not-unself-interested backing of neuroscience, which invested heavily in an egregious cephallocentrism that has swelled the heads of many humanoid researchers. The intelligence of the gut, however, has a more humble ambition. Our guts do not seek to distinguish us from other living beings; they do not affirm human specialness as a species imperative. Rather they remind us that “specialness,” insofar as it pertains to “species” in general, does not make us different from one another or from other life forms; the special is what we all have in common. The titles of two of the greatest children’s books of recent years, Everyone Poops and the equally important, The Gas We Pass, suggest that this is a lesson that all children can learn. Our guts remind us that we are not only a species, but also a kind of organism, the kind whose guts mediate our relations to each other and to the world, and thereby contain the vital paradox that we are. If we begin to appreciate that we are this kind of being, then our guts may help us to appreciate that kindness, even more than specialness, is a lively virtue — a virtue which our guts have known for quite some time.
~ Ed Cohen teaches Modern Thought in the Women’s and Gender Studies Department at Rutgers University. His most recent book is A Body Worth Defending: Immunity, Biopolitics and the Apotheosis of the Modern Body (Duke 2009). He is currently writing a new gut wrenching opus entitled Shit Happens: Ruminations on Living with Crohn’s Disease.
[i] Francisco Varela. “Organism: A Meshwork of Selfless Selves.” In Alfred Tauber, ed. Organism and the Origins of Self. Boston: Kluwer Academic Publishers, 1991. 85.
[ii] Adam Hadhazy. “Think Twice: How the Gut’s “Second Brain” Influences Mood and Well-Being.” Scientific American Online. http://www.scientificamerican.com/article.cfm?id=gut-second-brain. Accessed December 21, 2012.
Image: “Repair in progress,” Thirteen of Clubs, flickr.
Dr Alice Roberts reveals how your body tells the story of human evolution. The way you look, think and behave is a product of a 6 million year struggle for survival.