our second brain
Did you know our gut has its own brain?
If you read my previous post on probiotics you may know that our gut brain is called the Enteric Nervous System. The enteric nervous system allows for the gastrointestinal tract to work as a unit. This includes our esophagus, stomach, small & large intestines, liver, gallbladder and pancreas. This system is SO important that it has been referred to as our "second brain".
The Enteric Nervous System allows different areas to communicate about what is going on in the digestive system. It only takes 10 seconds for food to go from our esophagus into our stomach. Once in our stomach, it sits there for about 1-2 hours. Within this time, our stomach needs to let our intestines know what they are in for. Our stomach also needs to let our pancreas know to release digestive enzymes, and our gallbladder to release something called bile so that we can digest fat. Our enteric nervous system will relay all of this information as well as control how long the food stays in each part of the digestive tract. From the stomach, food should stay in the small intestine for around 3-4 hours before it spends around 18-24 hours in the large intestine. This means that the transit time from ingestion to excretion should be about 1-2 days. In many people, this isn’t the case… could this be an enteric nervous system dysfunction? This is a complicated question as there are also areas of the brain that control motility.
The enteric nervous system also communicates with the central nervous system in our brain and spinal cord. This connection is called the gut-brain axis and it allows for communication in both directions: from the brain to the gut, and from the gut to the brain. The microflora in our gut plays a large role in the health and function of this system. What is even more interesting, ~ there are more nerve fibres going from the gut to the brain, than from the brain to the gut (Rao 2016). This means the gut is doing a whole lot more of a brain-like job than our actual brain in this system.
How does this work?
Brain --> Gut
For example, when we are put under stress our sympathetic nervous system “fight or flight” is activated. This causes the release of our stress hormone cortisol from our adrenal glands. Our adrenal glands are these tiny glands that sit on top of our kidney that are responsible for many hormones including : cortisol (our stress hormone), testosterone & estrogen (our sex hormones) and aldosterone (helps control our blood pressure). Our adrenals also produce adrenaline (norepinephrine and epinephrine) that are also required during stress.
Okay, so we have stress hormones (cortisol and adrenaline) being released, but what do they do? They STOP our digestive system and instead UP REGULATE other systems that are needed for survival: a strong heart, big lungs and active muscles.
In comparison, when we are relaxed and not under stress our parasympathetic nervous system “wine and dine” or “rest and digest” takes over and it STIMULATES digestion. This is why one of the best keys to digestion is to eat in a relaxed state and avoid eating while running around right before, during or after.
Gut --> Brain
Let’s say we eat something we don’t agree with or get stuck with dreaded food poisoning: our gut transmits a signal to our brain to provide the sensation of nausea. What about if we ate too much? Our brain feels the sensation of bloating and satiety. How about when you eat your favourite food and feel happy after (or maybe that is just me), that can also be a result of the gut to brain connection as our gut produces 90% of our serotonin which is our happy neurotransmitter.
Research is now showing that eating things we have sensitivities towards may also cause anxiety and other similar symptoms. Treatments such as meditation, relaxation and hypnosis in which we are stimulating our “wine and dine” nervous system are relieving symptoms of gastrointestinal disorders.
Let's not forget that ~ 80% of our immune system is also located in our gut! This means it plays a significant role in immune reactions such as allergies, sensitivities, autoimmune disorders, other disorders caused by inflammation, and basically the health of our entire body.
There is also a significant amount of research being done on the brain-gut connection in diseases such as depression, autism, Parkinson’s, Alzheimer’s, ALS, MS and fibromyalgia. This is a very fascinating area of research that could change the way we look at many of these diseases.
Our enteric nervous system is the nervous system within our gut that often gets referred to as our “second brain”
Our enteric nervous system and central nervous system communicate via our gut-brain axis
The gut-brain axis is bidirectional meaning they both communicate with each other
Tip: avoid eating while your body is in “fight or flight” mode as our stress hormones shut down our digestive system. Instead, try eating when in “wine and dine” mode. Take a few deep breaths before eating, smell your food to get the gastric juices flowing and take your time eating.
Browning, K. N., & Travagli, R. A. (2011). Central nervous system control of gastrointestinal motility and secretion and modulation of gastrointestinal functions. Comprehensive physiology, 4(4), 1339-1368.
Carabotti, M., Scirocco, A., Maselli, M. A., & Severi, C. (2015). The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Annals of gastroenterology: quarterly publication of the Hellenic Society of Gastroenterology, 28(2), 203.
Furness, J. B. (2006). The enteric nervous system.
Gut-brain connection. Cleveland Health Clinic. Accessed 11/16/2019 : https://my.clevelandclinic.org/health/treatments/16358-gut-brain-connection
Rao M, Gershon MD. (2016).The bowel and beyond: the enteric nervous system in neurological disorders. Nature Reviews Gastroenterology and Hepatology. 13(9):517-28.
Rhee, S. H., Pothoulakis, C., & Mayer, E. A. (2009). Principles and clinical implications of the brain–gut–enteric microbiota axis. Nature reviews Gastroenterology & hepatology, 6(5), 306.
Stress and the sensitive gut. Harvard University. Accessed 11/16/2019: https://www.health.harvard.edu/newsletter_article/stress-and-the-sensitive-gut