Your second brainYou know that feeling of butterflies in your stomach before an important event? You aren’t just imagining it. It turns out, there is an entire network of neurons that line your gut. 100 million in total—more than you’d find in your spinal cord. There are so many neurons that some scientists call this network your “second brain.” Now, let’s be clear—there isn’t any conscious thought going on here. When you are contemplating the works of Descartes, your intestines aren’t chiming in. Rather, this network of neurons is responsible for all the mechanics of digestion. From squeezing food down the esophagus, to extracting nutrients in the intestine, this neural network is doing the work independent of your brain. But that’s not all. Your second brain also produces the vast majority of your body’s serotonin. Also known as the “feel good” neurotransmitter in your brain, interestingly enough 80%-90% of your serotonin is made and found in your gut. Serotonin is extremely important for instructing muscles to constrict, carrying impulses between nerves, regulating cyclic processes within the body, and regulating mood as well. In addition to serotonin, the bacteria that make up your microbiome produce their own set of important, influential chemicals. In a very real way, your gut is more responsible for your feelings than your head. Seems like ancient beliefs about “gut feelings” were onto something.
How bacteria change your moodHowever, one thing that the ancients didn’t understand is the microbiome. Even today, the interaction between your body and the bacteria that call it home aren’t all that well understood. In many ways, we’re still in the dark. We don’t understand how the interactions take place. But one thing we know for sure: Interactions are happening. Your microbiome is influencing the neurons in your gut, the production of serotonin, and your mood. In lab tests, we’ve been able to influence the mood and behavior of animals just by replacing their microbiomes. For instance, we can give a shy mouse the microbiome of an adventurous one—and it will become bolder and more adventurous. Or vice versa. We can give a normal rat the microbiome from an obese one, and the rat will immediately start to act like an obese one. There is even a tentative theory that a malfunctioning microbiome is responsible for autism in children—explaining why autistic children often also have gastrointestinal problems.
How to have a happy gutThe next few years will see a flowering of research in this new field, and I’m expecting a number of breakthroughs. We may discover that a malfunctioning microbiome is responsible for a whole host of psychological and physiological diseases, from autism to depression to who knows what else. In extreme cases, we may start treating some of these diseases with microbiome replacement—basically, cleaning out the old bacteria and putting healthy samples in their place. But there’s a simpler way to achieve the same thing, and to do it starting today. You see, in many ways, you’re responsible for your own microbiome. What you feed yourself has a huge influence on what bacteria thrive. And we know exactly what good bacteria like. So follow this simple three-step plan, and your microbiome will be in great shape:
- Eat prebiotics. Prebiotics are basically the favorite food of bacteria.
- Take probiotics. Probiotics are the healthy, good bacteria you want in your gut.
- Don’t kill the little ones. The easiest way to mess up a microbiome is by wiping out your current one.
- American Psychological Association, “That Gut Feeling”, Dr. Siri Carpenter, Sep 2012, Vol. 43, No. 8, page 50 http://www.apa.org/monitor/2012/09/gut-feeling.aspx
- Medscape, “The Gut Microbiome and Diet in Psychiatry: Focus On Depression”, Sarah Dash et al, Curr Opin. Psychiatry, 2015; 28(1):1-6 http://www.medscape.com/viewarticle/836260
- Medical News Today, “Serotonin: Facts, What Does Serotonin Do?”, James McIntosh http://www.medicalnewstoday.com/articles/232248.php
- Massachusetts General Hospital, “The Surprising Ways Bacteria In Your Gut Affect Your Moods”, Nov 2015, 4-5
- Scientific American, “Think Twice: How The Gut’s ‘Second Brain’ Influences Mood And Well-Being”, Adam Hadhazy, Feb 12, 2010 http://www.scientificamerican.com/article/gut-second-brain/