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McWhorter CNR Blog
gut brain connection

Which came first, the chicken or the egg? The relationship between ‘gut health’ and ‘mental health’ is a similar riddle. As far back as 1933, Neuropathologist Armando Ferraro said, “It is far from our mind to conceive that all mental conditions have the same [root cause], but we feel justified in recognizing the existence of cases of mental disorders which have as a basic [cause], a toxic condition arising in the gastrointestinal tract."

Medical Doctors and research scientists are more likely to focus on how the body affects the mind. Psychiatrists and psychologists tend to focus more on how the mind affects the body. Regardless, most health care providers have observed that one rarely comes without the other. Even medical doctors seek to treat gut conditions like IBS with antidepressants.

How does mental health affect gut health?

Chronic stress slows the activity of the intestines and disrupts the function of intestinal membranes. This activates the sympathetic (fight or flight) response which can either suppress digestion and or lead to urgent diarrhea. Bodies are only able to fully rest, digest, and heal when they shift from the stress state to the parasympathetic state. Gut dysfunction driven by stress can lead to or increase IBS symptoms such as abdominal pain, cramping, constipation, and/or diarrhea. Anxiety and depression have been shown in multiple studies to be highly connected to SIBO (Small Intestinal Bacterial Overgrowth syndrome) as well. Pain, discomfort and negative impacts on activities of daily living circle back to increase stress levels. This vicious feedback loop can be challenging to break.

Most people intuitively understand that there is a strong connection between our mental state and digestive tract. For example, English has multiple expressions such as:


  • I was so nervous. I had butterflies in my stomach.
  • I was so scared I almost pooped my pants.
  • Stop stressing about it so much. You are going to give yourself an ulcer.
  • He doesn’t have the guts to do it.
  • I had a sinking feeling in the pit of my stomach.

In English, we even refer to experiences of insight and intuition as gut feelings. Many are surprised to learn that there is a complex network of nerves and ganglia in the gut which can operate independently of the brain and central nervous system. This is called the enteric nervous system or the “gut-brain”. This secondary brain has more neurons in it than the spinal cord! The gut-brain speaks with the brain constantly through the vagus nerve and various hormones. The vagus nerve talks back to most of our organs and is responsible for controlling many aspects of our stress response. To put it short and simply, if the gut brain isn’t happy the brain isn’t happy... and the mind probably isn’t either.

How does gut health affect mental health?

Many neurotransmitters, such as serotonin, are produced in the gut itself. These compounds are crucial components in the healthy activity of a balanced nervous system. Disruption to a healthy gut sets the stage for a poorly functioning nervous system. Almost everything the body needs for healthy function comes into the body through the gut such as the amino acids needed to build neurotransmitters, iron for healthy blood and oxygen distribution, essential vitamins and minerals. Inflamed or dysfunctional intestines do not absorb nutrients as well. Some vitamins and essential compounds are manufactured in the gut by our microbiome. Deficiencies in these compounds are associated with anxiety, depression, fatigue, and ‘brain fog’.

What about the microbiome?

Most people are now aware that we need healthy levels of good bacteria in our gut for digestion and general health. Anxiety, depression and chronic stress can contribute to dysbiosis and vice versa. Dysbiosis is the overgrowth of the wrong type of bacteria or bacteria in the wrong part of the gut, such as in SIBO. Our microbiome (population and variety of bacteria in our gut) has significant impacts on our mental health. It is estimated that 9 out of 10 cells in the human body are in fact not human! So, it is not surprising that all of those organisms have such a strong influence on our physical and mental health.

Which approach is best?

Many individuals with IBS and SIBO have not experienced significant or lasting improvements with the conventional medical or counseling approaches due to a lack of integration. By the point that most people seek out complementary or alternative care, their conditions have progressed to having both significant physical and mental manifestations. It is important that their providers treat these as two sides of the same coin.

As a Naturopathic Doctor certified in Biofeedback therapy, Dr. Ryan Phillips has a diverse toolkit to address these conditions. He uses a combination of therapies for each patient based on scientific research, clinical experience, and the values and goals of the patient. Nutrition/hydration, lifestyle, movement, and sleep are the foundation for any intervention. Tools such as mindfulness, breathing exercises, biofeedback, and herbal/supplemental support are highly effective at reducing stress, anxiety, depression, and functional gut issues.

“Which came first, the chicken or the egg”, the physical condition or mental condition, is the wrong question to ask. What is most important is to understand the relationship between the different aspects of our health and what disrupted their functional balance.