How Your Gut Influences Your Mental Health: It’s Practically a Second Brain | Dr. Emeran Mayer
How Your Gut Influences Your Mental Health: It’s Practically a Second Brain
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We all feel things in our gut – intuitions that give us subtle physiological alerts, stress and anxiety that unsettle us, bad reactions to food, and conversely feelings of contentment from the right food, or flutters from an exciting experience.
But according to Dr Emeran Mayer, what we feel is just a small fraction of what’s going on in a region of our body that is still quite mysterious – even to the experts.
Dr Emeran Mayer is a world-renowned gastroenterologist and neuroscientist with 35 years of experience in the study of clinical and neurobiological aspects of how the digestive system and the nervous system interact in health and disease. His current research focus is on the role of the gut microbiota brain interactions in emotion regulation, chronic visceral pain, and in obesity. His research has been continuously supported by the National Institutes of Health.
Dr Mayer is a professor in the Departments of Medicine, Physiology and Psychiatry at the David Geffen School of Medicine at UCLA, executive director of the G Oppenheimer Center for Neurobiology of Stress and Resilience, and co-director of the CURE: Digestive Diseases Research Center at UCLA.
Emeran Mayer: The Mind-Gut Connection is something that people have intuitively known for a long time but science has only I would say in the last few years gotten a grasp and acceptance of this concept. It essentially means that your brain has intimate connections with the gut and another entity in our gut, the second brain, which is about 100 million nerve cells that are sandwiched in between the layers of the gut. And they can do a lot of things on their own in terms of regulating our digestive processes. But there’s a very intimate conversation between that little brain, the second brain in the gut and our main brain. They use the same neurotransmitters. They’re connected by nerve pathways. And so we have really an integrated system from our brain to the little brain in the gut and it goes in both directions.
The little brain, or the second brain, in the gut you’re not able to see it because as I said it’s spread out through the entire length of the gut from your esophagus to the end of your large intestine, several layers of nerve cells interconnected. And what they do is even if you – and you can do this in animal experiments if you completely disconnect this little brain in the gut from your main brain this little brain can completely take care of all the digestive processes, the contractions, peristaltic reflex, regulation of blood flow in the intestine. And it has many sensors so it knows exactly what’s going on inside the gut, what goes on in the wall of the gut, any distention, any chemicals. All of this is being picked up by these sensory nerves, fed into the interior nervous system, the second brain. And then the second brain generates these stereotypic responses. So when you vomit, when you have diarrhea, when you have normal digestion, all of this is encoded in programs in your second brain.
What the second brain can’t do it cannot generate any conscious perceptions or gut feelings. That really is the only ability that allows us to do this and perceive all the stuff that goes on inside of us is really the big brain and the specific areas and circuits within the brain that process information that comes up from the gut. Still most of that information is not really consciously perceived. So 95 percent of all this massive amount of information coming from the gut is processed, integrated with other inputs that the brain gets from the outside, from smell, visual stimuli. And only a very small portion is then actually made conscious. So when you feel good after a meal or when you ate the wrong thing and you’re nauseated those are the few occasions where actually we realize and become aware of our gut feelings. Even though a lot of other stuff is going on in this brain-gut access all the time.
When we talk about the connection between depression and the gut there’s some very intriguing observations both clinically but also now more recently scientifically that make it highly plausible that there is an integrate connection between serotonin in the gut, serotonin in our food, depression and gut function.
On a clinical level there’s a connection because many patients with depression also complain …
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