The Second Brain in Your Gut and How it Impacts Your Health

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Your gut influences much more than just digestion. From immunity to inflammation, mood, brain function, and more, your digestive system is intricately linked to key body systems and functions, connected by a vast network of signaling pathways—the primary one being the central nervous system and your brain.  

Your Gut’s Nervous System  

Gut functions, including microbiome activity, directly influence the health of our nervous system and vice versa, forming a powerful cross-communication network known as the gut-brain axis. The gut also has its own nervous system: the enteric nervous system (ENS) which consists of about 100 million nerves in the lining of the gut and shares many structural and chemical similarities to the central nervous system. Studies now estimate that the ENS contains more neurons than the spinal cord and show that it functions independently of the central nervous system. The role of the ENS is to regulate the vast functions of the digestive system.1,2 

The ENS produces many of the same neurotransmitters used by the brain, such as serotonin, acetylcholine, and dopamine. In fact, it’s estimated that a majority of the body’s neurotransmitters are created by the ENS in your gut, andnot the brain. For example, 90% of serotonin in the body is made in the gut. These gut neurotransmitters play key roles in regulating digestive functions. Beneficial microbes in the gut also produce neurotransmitters and other metabolic byproducts that directly influence the brain and nervous system, including gamma-aminobutyric acid (GABA), the calming neurotransmitter that helps reduce stress and anxiety.  

For these reasons, the gut is often referred to as “the second brain.”  

The Gut Brain Axis and Health 

Much of the gut-brain axis communication occurs through the vagus nerve, the largest craniosacral nerve in the body that connects the brain to the digestive system. This is in part why stress and mood disorders directly impact gut function. Over time, stress can cause serious imbalances in digestion and nutrient assimilation, as well as the production of neurotransmitters that impact brain function. On the other hand, inflammation in the gut from chronic digestive conditions can negatively impact the brain and trigger ongoing stress responses, depression, and serious neurological problems over time. Researchers now believe that the gut’s nervous system is responsible for the emotional changes including stress and anxiety experienced by people with irritable bowel syndrome (IBS) and other inflammatory gut health issues and symptoms. These connections are evidence that inflammation in the GI tract sends signals to the central nervous system (CNS) that result in mood imbalances. In addition, impaired digestion of protein reduces the number of amino acids available to support neurotransmitter production. This can directly impact mood, sleep, cravings, and other issues.3,4 

Microbiome, Brain, and Mood   

The trillions of bacteria living in the gut (and other areas of the body) are called the microbiome, and as research continues to show, these bacteria have significant roles in total-body health and function. Typically, a healthy gut has a balance of about 80% beneficial microbes, and 20% unhealthy microbes, which is considered normal to keep gut immunity actively functioning. However, when unhealthy microbes outnumber beneficial ones, a state of gut dysbiosis develops. Dysbiosis causes gut inflammation and damage and can significantly impact the health of the brain and nervous system, as well as normal digestive function. Research continues to demonstrate how changes in gut microbiota can influence behaviors related to anxiety and depression. Damage to microbiome populations also reduces the production of neurotransmitters in the gut, resulting depression, anxiety, and other mood imbalances.5 Dysbiosis has also been linked to multiple sclerosis, autism spectrum disorders, Parkinson’s, and other neurological conditions.  

Natural Solutions to Improve Your Gut Health  

Because of these vast interconnections, improving our digestive health and overall gut function with natural approaches is a key strategy for supporting a healthy brain and mood, reducing stress and anxiety, improving sleep, and defending neurological function—in addition to supporting other key areas of health such as immunity and energy.  

Foods to Avoid for a Healthy Gut 

There are many commonly consumed foods that can have a catastrophic effect on digestive function. These foods fuel inflammation, promote the growth of unhealthy microbes, and can damage gut function over time. Dairy is an example of a food that is problematic for many people, as lactose can be difficult to digest, causing gas and bloating. Gluten from wheat, barley or rye can also fuel inflammation. Gluten intolerance appears to be on the rise, though some researchers believe that the issue comes from the glyphosate and other pesticides sprayed on wheat. Gluten issues can be difficult to diagnose, but if you feel better after eliminating it, it’s best avoiding gluten whenever possible.  

The most impactful and harmful aspect of our modern diet on our guts is the abundance of processed foods and factory-farmed meats. The chemicals, rancid oils and trans-fats, bacteria-laden factory meats, and refined carbohydrates in processed foods fuel inflammation and can cause several digestive and other health issues. Other digestion-damaging ingredients include caffeine, alcohol, prescription, and OTC drugs. These can cause acid imbalances and harm beneficial bacteria.  

Gut Healthy Foods  

Whole unprocessed foods that provide adequate fiber are high on the list of natural ingredients that can support healthy digestion and overall gut health. Fermented, probiotic foods such as yogurt, kefir, sauerkraut, and kimchee can be particularly helpful for gut health and digestion, supplying beneficial bacteria that are essential for a healthy gut. 

We can also add nutrients called “prebiotics” to feed the bacteria. Prebiotics are special carbohydrates that support probiotic bacteria and help create a hospitable environment for them to populate. Prebiotics can be found in supplements, usually as “fructooligosaccharides” or FOS, as well as foods like artichokes, garlic, onions, chicory and others.  

In my practice, I recommend a powerful probiotic formula that delivers 8 clinically-studied strains of live beneficial bacteria, together with prebiotic nutrients and 19 digestive herbs to support optimal gut function, and rebuild a healthy microbiome.  

Stress Relief for Digestion  

One of the best ways to support digestion and enhance the gut-brain connection, is with healthy stress relief practices that incorporate mind-body methods to help relieve stress and tension throughout the body. Yoga, Tai Chi, and mindfulness meditation are powerful healing methods that can strengthen the vagus nerve and promote greater resilience to stress, while improving gut function, mood and brain health—as well as other key areas of health. 

One pilot study found that regular meditation practice significantly improved symptoms of Irritable Bowel Syndrome (IBS) and inflammatory bowel disease. After 9 weeks, participants experiences less pain, improved stress levels, reduced inflammation, and other key benefits.6  

The more we learn about the gut-brain connection, the more we understand how our lifestyles, diets, and daily habits can influence key areas of health, with far-reaching impacts. By taking the steps to support optimal gut health naturally, we can see improvements in mood, brain function, neurological wellness, and long-term, total-body health.  

(1) Strandwitz P. Neurotransmitter modulation by the gut microbiota. Brain Res. 2018;1693(Pt B):128-133.  

(2) Nezami BG, Srinivasan S. Enteric nervous system in the small intestine: pathophysiology and clinical implications. Curr Gastroenterol Rep. 2010;12(5):358-365.  

(3) Stevens BR, Goel R, Seungbum K,et al. Increased human intestinal barrier permeability plasma biomarkers zonulin and FABP2 correlated with plasma LPS and altered gut microbiome in anxiety or depression. Gut 2018;67:1555–7. 

(4) Banerjee A, Sarkhel S, Sarkar R, Dhali GK. Anxiety and Depression in Irritable Bowel Syndrome. Indian J Psychol Med. 2017;39(6):741-745.  

(5)Maes M, Kubera M, Leunis JC, Berk M. Increased IgA and IgM responses against gut commensals in chronic depression: further evidence for increased bacterial translocation or leaky gut. J Affect Disord. 2012 Dec 1;141(1):55-62.  

(6) Sue McGreevey. Meditation may relieve IBS and IBD. The Harvard Gazette website. Updated May 5, 2015. Accessed February 28, 2022.  

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