Our gut is more than a place to digest food for fuel.
Did you know that there is a communication pathway that flows from the gut to the brain?
That the gut has a vital role in our immune system?
That the gut has a relationship with our endocrine system?
And you guessed it - they all have ties to our mental health.
I know, I know I always land there - but it’s TRUE!
Here is What I’m Going to Share With You About Your Gut & Mental Health:
The Gut-Brain Connection
Understanding the Guts Role in Our Immune System
Understanding the Way the Gut Works With Our Hormones
Healthy Gut - Healthy Mind
The Gut-Brain Connection:
The gut-brain connection communicates in a variety of ways. 1. Vagus Nerve - The longest nerve in the body connecting your brain to many important organs. Including the intestines, stomach, heart, and lungs, and is a key part of our parasympathetic nervous system. The vagus nerve influences breathing, digestive function, and heart rate - all of which can have a huge impact on our mental health.
80 - 90% of nerve fibers in the vagus nerve are for transmitting information from the gut to the brain, rather than the brain to the gut.
The role of the vagus nerve in digestion:
- Motility - Helps food move through the digestive tract
- Digestion - Stimulates the release of digestive enzymes
- Appetite - Communicates satiety and hunger to the brain
2. Microbial Metabolites - Chemical compounds form and/or convert into other different compounds that communicate with cells to serve as messengers (neurotransmitters).
These chemical messengers are utilized for gut function and nerve activity, never crossing the blood brain barrier, yet influence brain function.
The gut produces:
- 90% of the body’s serotonin
- 50% of the body’s dopamine
- 99.5% of the body’s melatonin
Keep in mind that neurotransmitters such as serotonin, dopamine, and melatonin have multiple functions other than mood - functions such as digestion, sleep, and cofactors. Yet, all these functions are still connected to the mind.
3. Inflammation - Chronic states of inflammation send signals via the vagus nerve to the brain translating danger:
Influence how neuro-chemicals are produced
Have a negative impact on energy production and cellular death
Impacts stress hormones (specifically cortisol)
Proliferates cytokines - increasing likelihood for even more depression (2)
Understanding the Guts Role in Our Immune System:
Thanks to the Human Microbiome Project and growing research we are learning daily that our immune system and the root of our mental health actually live in and around our gut (called GALT - gut-associated-lymphatic tissue).
Up to 80% of our body’s immune system is accounted to GALT.
The intestinal wall is the barrier to the outside world - aside from the skin it has the most chances for bodily defense. (3)
Any potentially harmful substance in the gut will send a message to the rest of the immune system. This is one reason food choices are so important to immune health and as we are learning - important to brain health as well.
The Microbial Flora in our Gut Has Many Roles and Duties:
Aides in absorption of nutrients
Creates a barrier from harmful invaders (bad bacteria, viruses, and parasites)
First step of detox (helping take the load off the liver)
Production of enzymes, vitamins, amino acids, and neurotransmitters
Help stabilize stress hormones
Regulates inflammatory pathways
The gut is our biggest immune organ - controlling the immune systems response and actions.
Understanding the Way the Gut Works with Our Hormones:
Growing evidence suggests that our gut microbiota is a key factor in the metabolism of hormones, and in turn those hormones greatly influence our microbiota.
Gut hormones identified in mood disorders such as anxiety and depression serve as signals in the gut-brain axis as well as our energy metabolism. All of these hormones are released in response to food in-take and work to regulate different functions of our central nervous system. Making the endocrine system the other factor identifying what is going on between our brain and our gut. (4)
Hormones and Your Central and Enteric Nervous Systems:
Central Nervous System (CNS) connects the brain to the spinal cord.
Enteric Nervous System (ENS) runs from the mouth to the anus - same neurons and neurotransmitters found in our CNS.
The ENS communicates with our brain through the nervous system and our hormones. Remember an exchange of information also takes place between our gut and the immune system - affecting our overall mental health.
Both CNS and ENS are connected via the vagus nerve.
Gut microbiota can exert considerable influence on our CNS. Microbiota have the ability to produce neurotransmitters that facilitate and play a role in sleep and sleep regulation, appetite, mood, and pain. All essential for mental well-being.
The CNS helps regulate the intestinal function via the hypothalamic-pituitary-adrenal axis (HPA).
Stress produces a cascade of events in the HPA axis. The HPA axis is a self-regulatory system using cortisol to regulate its own activity through a negative feedback loop depending on the levels. Changes in the HPA axis loop affect many physiological systems, including the immune system. Chronic stressors also affect the release of hormones such as norepinephrine and serotonin, pro-inflammatory cytokines and inflammatory pathways in the brain, endocrine glands and blood.
Cortisol:
Cortisol is the body’s stress hormone, but also controls how our body processes carbohydrates, fats, and proteins. Known as our fight or flight hormone during times of stress - increasing appetite, storing fat, and breaking down protein.
Excess cortisol over time can lead to access abdominal fat, bone loss, suppress immune system function, fatigue, increased risk for insulin resistance, heart disease, and depression. (3)
Cortisol is also a buffer against inflammation - when cells become resistant to cortisol one result is chronic inflammation. (5)
Inflammatory agents transfer information to the CNS - like the vagus nerve - which we know connect the brain to the gut .
Healthy Gut - Healthy Mind:
Gut Microbiota Facts and Function:
10 microbial cells to every human cell
Immune health
Extracts nutrients from food - synthesizing vitamins
Fermenting fibers to create short-chain-fatty-acids
Bile acid metabolism
Production of neurotransmitters (norepinephrine, tryptamine, serotonin, dopamine, GABA)
Our gut is home to trillions of bacteria collectively called our microbiome.
Our microbiome allows for nutrients to enter the body, keeping opportunistic pathogens out, and helping our brain function.
The gut microbiome ecosystem are key players in our mood and overall mental health; helping with depression and anxiety, but can also make matters worse.
If our microbiome is out of balance (dysbiosis) that will effect our overall mood.
Knowing the relationship between the vagus nerve explains why stress can play a role on our digestion and why digestive issues play a role in our mood.
When the vagus nerve is impaired by stressors it cannot react adequately to inflammation - which we know is bad for our gut and microbiome.
To support our health our microbiome needs to be diverse.
Diversity is what helps keep it in balance.
Dysbiosis results in opportunistic bacteria to proliferate and ultimately cause inflammation.
Which, as we are learning can contribute to depression and depression can cause inflammation.
At its basic level our diet can help our gut microbiome protect our mental well-being because the right food feeds the right bacteria.
When you eat plenty of healthy diverse foods, our microbiome is more diverse and is able to generate neurotransmitters such as serotonin and GABA.
Whew! I know that was a lot - my hope is to educate and open the doors for you to see the relevance of all the inter-connective systems in our bodies and their relationship with food.
Join me next month when we will be jumping more into the role inflammation and inflammatory foods have on our mental heath well-being.
References:
Breit S, Kupferberg A, Rodler G, Hasler G. Vagus Nerve as a Modulator of the Brain-Gut Axis in Psychiatric and Inflammatory Disorders. Front Psychiatry. 2018; vol 9:44. doi: 10.3389/fpsyt.2018.00044.
Himmerich H, Patsalos O, Lichtblau N, Ibrahim M, Dalton B. Cytokine Research in Depression: Principles, Challenges, and Open Questions. Front Psychiatry. 2019; vol 10: 30. doi: 10.3389/fpsyt.2019.00030.
Brogan K MD, Loberg K. Mind of Your Own. Thorsons. 2016.
Sun L, Li J. Nie Y. Gut Hormones in microbiota gut-brain cross talk. Chin Med. 2020; vol 133(7): 826-833. doi: 10.1097/CM9.0000000000000706.
Cohen S, Janicki-Deverts D, Doyle W, Miller G, Frank E, Robin B. Chronic stress, glucocorticoid receptor resistance, inflammation, and disease risk. Proc Natl Acad Sci USA. 2012; vol 109(16): 5995-5999. 10.1073/pnas.1118355109.