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April 2020

Second Brain in Gut: Please Explain

Have you ever felt that feeling in your gut when things don’t seem quite right? Or that feeling of butterflies when you’re a little nervous. This isn’t just a “feeling” it is your “second brain” sending you a signal.

Your “second brain” resides in the walls of your digestive system and recent studies are changing how we understand the link your digestive system has with your mood and even the way you think.

Technically known as the enteric nervous system (ENS), the second brain consists of two thin layers of more than 100 million nerve cells that line your gastrointestinal tract. During fetal development the enteric nervous system progresses from the same tissues as your central nervous system, making its structures and chemical responses very similar to the brain.

The main role of the ENS is to control digestion, release enzymes that break down food and control the blood flow that helps with nutrient absorption and waste elimination. And although our “second brain” doesn’t make executive decisions like our actual brain, the two do communicate back and forth via electrical impulses through a pathway of nerves, known as the gut-brain axis, and this pathway influences our endocrine, immune and neural systems; even your microbiome can release neurotransmitters that speak to the brain and influence your perception of the world and alter your behavior.

So whilst your gut bacteria has an impact on the brain, the brain also influences the gut microbiome, the feedback then reverts back to the brain to influence your behavior, going back and forth constantly.

Disruptions in the brain-gut communication are associated with inflammation, chronic abdominal pain, eating disorders and psychosocial stressors.

What is coming to researcher’s attention is that our ENS can trigger big emotional shifts. Have you ever felt upset, anxious or stressed about something and symptoms such as constipation, diarrhea and bloating come along as well? Maybe you are in the office and you have to give a presentation or do a talk in front of a big group of people, do you sometimes feel it in your tummy?

Researchers are now beginning to discover the two way street between gut symptoms and emotional feelings.

Another way your gut is influencing your moods is through the trillions of bacteria within the gut. Gut bacteria can affect your behavior and moods every minute of every day. An imbalance of beneficial bacteria versus harmful bacteria (dysbiosis) has been linked to a number of psychiatric and neurological disorders such as anxiety, depression and stress, this is potentially due to the pro-inflammatory states created by the bacteria imbalances within the gut.(1)

Certain good bacteria can also generate a “feel good” feeling, so by having an environment which helps feed and house these bacteria strains will further contribute to a happier mood.(2)

Studies done on mice have shown that by manipulating their gut bacteria, behaviors relating to anxiety and depression can be influenced. With studies showing that by replacing the gut bacteria of anxious mice with the bacteria from more fearless mice an increase in their sociability and decrease in their anxious behavior was observed (this also worked in reverse). Also through changing the diet of the anxious or aggressive mice and introducing a probiotic strain, these mice became a lot calmer.(3)

Another contributing fact is that 90-95% of the body’s serotonin levels are stored in the gut with only 5-10% stored in the brain. Serotonin is a neurotransmitter that plays a major role in controlling your mood. The right amount of serotonin will have you feeling relaxed and positive, but imbalances in serotonin attribute to feelings associated with depression and can also impact your appetite, sleep, memory and social behavior. Skewed levels of serotonin can also cause constipation or diarrhea.

So how can you support both your gut and your brain? It all lies in the health of microbiome. By supporting the growth of healthy bacteria and encouraging diversity within the gastrointestinal tract you can reduce hypersensitivity and leaky gut permeability and normalize brain levels of stress hormones. Improving the quality and health of your friendly gut bacteria will also improve mental health and overall wellbeing.

The following foods are fantastic in supporting gut health and supporting serotonin production. Plus please enjoy a few of my favorite mood boosting recipes with videos!

  • Eggs – the protein in eggs can significantly boost your blood plasma levels of tryptophan, the amino acid that serotonin is biochemically derived from.
  • Nuts and seeds – also contain tryptophan and are fantastic sources of fiber, vitamins and antioxidants.
  • Foods high in Vitamin B6 such as spinach, cauliflower, garlic, fish, celery, poultry and lean beef - play an important role in helping your body produce serotonin.
  • Fermented foods - help assist in the digestion and absorption of all the important nutrients you need for serotonin production.


About the Lee Holmes series and our partnership

Gut health is important for your mental health and overall wellness, it’s one of the most important components of the body. We interact with it daily and it’s something intricately connected to many aspects of our everyday life.*

OnePath Life Limited (OnePath Life) is committed to deliver market leading mental health and wellness solutions with a focus on service, customer wellness and prevention. The focus on mental health and wellness is at the core to OnePath Life’s proposition. To deliver on our commitment, we have developed a suite of tools, education pieces, and collaborated with partners to provide our customers with the support they may need to facilitate a healthy life. OnePath Life has proudly partnered with Lee Holmes to provide education and nutritional inspiration for our customers to supercharge their health.


  1. Foster J.A. and McVey Neufeld, K. Gut Brain Axis: How The Microbiome Influences Anxiety and Depression. Department of Psychiatry and Behavioural, 2013. 36(5): 305-12. Neurosciences http://www.psych.ufl.edu/~dpdevine/bb/pelham.pdf
  2. Javier A. Bravo, et al. Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve. PNAS 2011 : 1102999108v1-201102999. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3179073/
  3. Hsiao, E.Y. The Microbiota Modulates Gut Physiology And Behavioral Abnormalities Associated With Autism. Cell, 2013. 155(7): 1451-1463. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3897394/

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