Home » Resources Library » 5 Ways Gut Health Affects Mental Health

5 Ways Gut Health Affects Mental Health

By Erin McNamara

Last Updated:


Have you ever had a “gut feeling” about a situation? How about feeling “butterflies” in your stomach? Chances are at some point you’ve experienced these types of feelings. These feelings are examples of the connection between your gut and brain.

The gut-brain axis is the term used to describe the two-way communication between the brain in your gut and the brain in your head. Yes, you read that correctly, there’s a brain in your gut! This brain is constantly communicating with the one in your head. 

So how does it do this? The communication is between the central and enteric nervous system via the vagus nerve. The vagus nerve is the longest of the cranial nerves and it travels out of the brain into your stomach and intestines. The gut then picks up these messages from the brain through its own nervous system (enteric) and responds accordingly. 

Recently, research has discovered an important link between the gut microbiota and its influence on these interactions. The gut microbiota, also known as gut flora, is the microbe (teeny tiny living organisms) population that lives in our intestines. Our gut microbiome contains a crazy number of microorganisms. These microorganisms include at least 1000 different species of bacteria with more than 3 million genes! In fact, our gut contains 3 to 5 pounds of bacteria.[1]

Importance of gut health


Why is the gut microbiota important? 

Gut microbiota plays an important role in many functions that impact health. It helps digest certain foods, helps with the production of certain vitamins, and plays a role in the immune system. A balanced and healthy gut microbiota is really key for proper digestive functions. Dysbiosis is when there is a loss of balance in the gut and could be linked to certain health issues. This imbalance is often due to the overgrowth of bad bacteria or lack of good bacteria which leads to inflammation in the body. 

Dysbiosis originates in the gut but you can have it without displaying any noticeable digestive symptoms. Many symptoms of gut dysbiosis manifest in other ways throughout the body. The disrupted gut microbiome can cause a variety of cognitive and mood disorders.

How Can Gut Health Affect Mental Health?

Gut Health Can Trigger Depression

It’s estimated about 1 in 5 people will experience depression at some time in their life. Medications that increase serotonin can be an effective treatment. Serotonin is a chemical known to be a contributor to happy feelings. But these medications don’t work for more than a third of depressed people. The latest theories suggest an imbalance in the gut microbe and dysfunction in the gut-brain axis may be the culprit.

New research shows depressed people have less diversity and less rich gut microbiota than those who don’t suffer from depression. Gut microbiota influences the hypothalamic-pituitary-adrenal (HPA) axis, which regulates stress response and cortisol release. This research showed that depressed people have an impaired HPA axis causing an increase in the release of cortisol, a stress hormone.[2]

Gut Health Can Affect Your Focus


Brain fog is a term used when people have fuzzy thoughts, trouble concentrating or recalling memories. You may feel like you are unable to think clearly, or you just don’t feel like yourself. Research indicates a leaky gut may be the cause of your brain fog. 

A leaky gut syndrome is when the lining of the gut has cracks or holes which allow undigested food, toxins, and other pathogens to escape into the bloodstream. This leads to changes in gut flora and inflammation. Inflammation causes the brain to work extra hard causing inflammatory oxidative stress in the hypothalamus. This stress causes brain fog and continues until the gut lining is repaired.[3]

Anxiety is an intense and persistent feeling of fear and worry. Often these feelings are difficult to control and can interfere with daily activities. A healthy gut promotes a normal stress response via the HPA axis. Alterations in the gut microbiota can cause the HPA axis to malfunction which produces an exaggerated stress response, aka anxiety.

Recent research has indicated anxiety may be treated by regulating the gut microbiota with probiotics. 

Probiotics are living organisms naturally found in foods and are often called “good bacteria”. This “good” bacteria helps fight off the “bad” bacteria in the gut. By replenishing the gut to a happier environment, the HPA axis can get back t functioning properly and anxiety symptoms appear to be alleviated.[4]

Gut Health Is Directly Linked To Energy Levels


The quality and timing of our sleep patterns are closely linked to our mental health. Recent evidence suggests the gut microbiota can influence sleep quality and our circadian rhythm. 

Research conducted on people with Chronic Fatigue Syndrome showed higher levels of “bad” bacteria in the gut. These bacteria are associated with an increase in sleep problems and fatigue in females. Other evidence suggests an imbalance in our gut may be the root of sleep issues. Gut bacteria can heavily influence the regulation of our “body clock”. These gut microbes move according to a rhythm during the night and day. Fatigue can disrupt how well this movement goes causing changes in the pattern of these microbes.[5]

You May Experience Mood Swings

Changes in mood from day to day are normal but when you switch from extremely happy to extremely sad on an everyday basis this may indicate an underlying condition. Your mood can be influenced by certain hormones in the body. If your gut is imbalanced your production of certain hormones may be affected. 

For example, gut microbes produce an enzyme that can increase levels of estrogen. When the gut is inhabited with good bacteria, it can metabolize and recycle estrogen in your body properly. But when the gut is imbalanced by bad bacteria it can prevent excess estrogen from being excreted from the body. The inability to properly excrete the excess hormone results in a buildup of too much estrogen. High estrogen levels can cause alternating feelings of happiness and sadness.[6]


  1. Gut microbiota infogutmicrobiotaforhealth.com. Retrieved on January 18, 2020.
  2. Evrensel A and Ceylan ME – The Gut-Brain Axis: The Missing Link in Depression. Published on December 31, 2015.
  3. Stefania Schiavone, Vincent Jaquet, Luigia Trabace, and Karl-Heinz Krause – Severe Life Stress and Oxidative Stress in the Brain: From Animal Models to Human Pathology. Published on April 20, 2013.
  4. Anxiety might be alleviated by regulating gut bacteriasciencedaily.com. Retrieved on January 18, 2020.
  5. Wallis A, Butt H, Ball M, Lewis DP, and Bruck D – Support for the Microgenderome: Associations in a Human Clinical Population. Published on January 13, 2016.
  6. Baker JM, Al-Nakkash L, and Herbst-Kralovetz MM. – Estrogen-gut microbiome axis: Physiological and clinical implications. Published on June 23, 2017.