The Gut-Brain Connection

August 20, 2019

The Gut-Brain Axis

Our digestive system has a mind of its own called the enteric nervous system (ENS). The ENS is responsible for deciding when we need to release digestive enzymes to break down our food, how much blood flow the digestive system needs, and the speed at which food travels through our digestive tract.

The ENS also communicates back and forth with our brain. The main receiving and transmitting areas of the brain that our gut communicates with are the limbic system and prefrontal cortex. These areas are responsible for processing emotions, storing memories, regulating fear-based responses, self-awareness, judgment, motivation, and behaviour.

Our gut uses the same neurones and neurotransmitters that our brain dose. In fact, our gut makes 90% of our serotonin, which is our “feel good” neurotransmitter, and 50% of our dopamine, which is our “reward” neurotransmitter.

The connection between our gut and the brain is bidirectional. This connection creates a similar philosophical question to the “chicken and egg” conundrum.

This has lead many researchers to be stumped over the cause and effect between mood and digestive conditions. For example, does anxiety aggravate Irritable Bowel Syndrome (IBS), or does IBS aggravate anxiety?

Our microbiome’s role in the Gut-Brain Axis

Our microbiome, the billions of bacteria that live in our digestive tract, also plays a role in the gut-brain connection. Our microbiota can influence our metabolism, mood, cravings, behaviour, immune system and the HPA axis (read my blog on ‘What Causes Stress’ to learn more about the HPA axis).

A study by Sudo et al. demonstrated that “germ‐free” mice (who’s microbiome have been removed) have an overactive HPA axis in response to stress, meaning they are more sensitive and susceptible to stressors.

Also, mice with a sterile digestive tract showed a 60% reduction in serotonin levels, and when they digestive tract was re-populated with bacteria, serotonin levels returned to normal.

Another study by Bailey et al. demonstrated that long term stress has also been shown to affect the health and reduce the numbers of microbiota species in our digestive tract.

Again, was it the chicken or the egg that came first?

How to Support the Gut-Brain Axis

More research is needed to clarify the cause and effect relationship between our digestive system and emotional wellbeing. However, there are a few simple tips you can incorporate into your daily routine to support a healthy gut-brain connection.

  1. Stress management & Mindfulness practices: use whatever techniques works best for you to help reduce stress in your life, this can include meditation, exercise, breathing exercises, yoga, being in nature, etc.

  2. Exercise at least 150 mins per week: Exercise has been shown to reduce stress, improve mood and improve digestion regularity.

  3. Eat whole foods: focus your meals on natural whole food like organic fruits, vegetables, whole grains, nuts, seeds and ethical meats to ensure you are feeding your microbiome and ensuring a healthy digestive system.

  4. Limit inflammatory foods: try to avoid foods that will cause irritation to the lining of the gastrointestinal tract, such as sugar, artificial flavourings, artificial colourings, processed meats, white bread, and common food sensitivities like gluten and dairy.

  5. Increase fermented food: include healthy probiotic foods like sauerkraut, kimchi and miso into your diet to help maintain a healthy microbiome. You can also speak with your healthcare provider about which probiotic supplements may be best for you.

Thank you for reading! Wishing you all the best in your journey to health and wellness.

In health,

Dr. Fiona


Bailey MT, Coe CL. Maternal separation disrupts the integrity of the intestinal microflora in infant rhesus monkeys. Dev Psychobiol 1999; 35: 146–55.

Clarke G, Grenham S, Scully P et al. The microbiome‐gut‐brain axis during early life regulates the hippocampal serotonergic system in a sex‐dependent manner. Mol Psychiatry 2013; 18: 666–73.

Sudo N, Chida Y, Aiba Y et al. Postnatal microbial colonization programs the hypothalamic‐pituitary‐adrenal system for stress response in mice. J Physiol 2004; 558: 263–75.