There is so much more going on in your sleep than you think.
In his first video for Big Think, Dr Emeran Mayer – gastroenterologist and author of The Mind-Gut Connection – described what is called our “second brain”. The gut is no ordinary body system; it’s intelligent and independent, in that it consists of about 100 million nerve cells sandwiched between layers of the gut running all the way from the esophagus to the end of the large intestine. This ‘second brain’ in our gut, and our regular brain use the same neurotransmitters and are connected through neural, endocrine, and immune pathways, so it truly is an integrated intelligent system with information flowing in both directions.
This becomes interesting when you start asking questions about sleep and its relationship to health. We all know sleep is vital to bodily function, but usually we’re focused on our mind activity. What are we dreaming about? Are we processing the day’s emotional turbulences? Are we getting enough sleep to let the brain do its thing?
Dr. Mayer explains that your gut is also critically important during sleep, and is affected by your sleep patterns. When you fall asleep and your stomach is empty, your gut commences 90-minute cycles of intense contractile waves that migrate from your esophagus all the way down to the end of your large intestine. It’s a cleaning process that removes residue from the gut and keeps microbial bacteria in check. We’ve always known that missing out on sleep makes us foggy-headed and far from our best selves in terms of cognition, but if our sleep is disturbed or we aren’t getting enough of it, or we are eating too much in the night, the gut won’t have a chance to properly clean itself. Left unregulated, bacteria will develop into abnormal colonies, the health implications of which can be enormous.
What’s more, Mayer points out that, in a way, your gut dreams too. Just as the expressions on your face reveal your internal emotions, your gut is equally reflective of your daily ups and downs – whether it takes the form of butterflies, nervous bowels, emotional nausea, or more subtle physiological changes that fly under the radar. And just as an event that didn’t really seem important in the daytime can completely take over your dreams at night, your gut too is encoded with these experiences and must digest them. “Many of these memories have a gut-feeling component because every time we have an emotion during the day there’s always a counterpart at the gut level that, through these sensory pathways, goes back to the brain.” During sleep, memories are retrieved and processed in the brain, which includes re-living the corresponding gut feelings we had during the day.
With this insight, one has a whole new appreciation for the gut or “second brain”, and its nocturnal mechanisms are a fascinating and urgent reminder that sleep is more important than ever.
Dr Emeran Mayer's most recent book is The Mind-Gut Connection: How the Hidden Conversation Within Our Bodies Impacts Our Mood, Our Choices, and Our Overall Health.