The Gut-Brain Axis: What to know

30 Apr 2021
Lauren Aucoin

The Gut-Brain Axis: What to know

Recent news has highlighted a connection between what you eat, and how you feel- not just physical health wise, but mental health as well. In this blog post, we dive into the science behind these claims, and how they relate to your daily life.

Prior research has demonstrated an association between depression and obesity. 55% of individuals living with obesity have depression. Furthermore, individuals living with depression are 58% more likely to experience obesity1. This correlation is well known however, until recently causality and specific details on the connection between what one eats and their mental health has remained unknown. Recent studies have focused on the relationship between what you eat and your mental health, specifically looking into the gut-brain axis2.

What is the Gut-Brain Axis?

The gut-brain axis is a broad term to encompass the various interactions between the peripheral digestive system and the brain. Specifically, the microbiome and probiota of the digestive system are essential in this communication. Many of us have heard of “probiotics”, which are based on the concept of introducing “healthy” bacteria to the digestive system. The gut-brain axis builds upon this concept of bacterial populations in the digestive system and looks to see the impact of this microbiome beyond the digestive system.

 

The Gut-Brain Axis and Mental Health

A great deal of the research on the gut-brain axis has focused on the immune system. However, emerging research has focused on the relationship between the microbiome of the digestive system and mental health.

GABA Receptors

GABA receptors are hormone receptors in the brain which control relaxation. One study found that constant treatment with antibiotics, which work to deplete the gut microbiome, decreased the amount of GABA receptors found in key brain areas3. By decreasing the receptors associated with relaxation, this had the inverse effect of causing increased anxiety and depression-like symptoms. This study provides a concrete example of how disrupting the gut microbiome has mental health repercussions.

Mechanisms of Communication

How does this communication occur? Research suggests there are a variety of ways in which the gut communicates with the brain. One way is through the Vagus Nerve. This nerve senses changes in the composition of the digestive system and sends a signal straight to the brain. Another important way is through gut permeability. Our intestines are lined with cells which are connected by proteins to keep the cells in place in place and make sure that the contents of our intestines are not able to leak out. Once these cells get leaky, a variety of problems occur. Interestingly, studies have shown that treatment with probiotics is able to return these connections to their normal states,  which has also been connected to treating the symptoms of some mental health conditions4.

One other key pathway in which your digestive system may be impacting your brain is through inflammation5. Issues with your digestive system have been linked to increased activation of the immune system. The immune system being activated causes inflammation: think of how you run a fever and have sore joints when you catch a cold. The problem occurs when issues with your digestive system and immune system cause long term, subtle, inflammation. This can have damaging effects on the brain, causing many of the associated mental health problems.

The Ted Talk linked below has more details on this interesting topic:

https://www.youtube.com/watch?v=FWT_BLVOASI

With all this knowledge, what can you do to prevent these issues?

Healthy Eating Means a Healthy Gut

The composition of your digestive system is based off of the foods you ingest. Diets high in added sugars are associated with inflammation6. However, diets high in vegetables, protein, and healthy fats are associated with a healthier digestive system and connected to better mental health.

 

The foods you eat don’t only impact your digestive system; they also impact your brain. In a 2015 study, patients who ate primarily a Mediterranean diet were found to have reduced likelihood of depression in a 7-year follow-up period 7. Diets rich in legumes, vegetables, nuts, fruits, and moderate amounts of lean poultry and fish are associated with a healthier gut microbiome 8.

 

This article does not serve as a strict set of instructions or as a comprehensive treatment plan for mental health conditions. A proper treatment plan for depression, anxiety, or any other mental health condition is best made with the help of a medical professional. However, research has demonstrated that our food choices have a direct impact on our brain and mental health.

Sources

  1. https://www.mentalhealth.org.uk/a-to-z/d/diet-and-mental-health#:~:text=There%20is%20research%20to%20suggest,associated%20with%20feelings%20of%20wellbeing.
  2. https://www.health.harvard.edu/blog/nutritional-psychiatry-your-brain-on-food-201511168626
  3. https://www.pnas.org/content/108/38/16050
  4. https://pubmed.ncbi.nlm.nih.gov/24372793/
  5. https://www-ncbi-nlm-nih-gov.proxy.library.nd.edu/books/NBK5243/
  6. https://www.medicalnewstoday.com/articles/326386
  7. https://www-ncbi-nlm-nih-gov.proxy.library.nd.edu/pmc/articles/PMC4454450/
  8. https://www.medicalnewstoday.com/articles/326744#The-Mediterranean-diet-benefits-gut-health