Not everything is in your head. Meditation is not the only solution to mental health conditions. Mental health has a lot to do with our gut-microbiome. There are a lot of scientific papers that have been written on this undeniable connection. Although there are healing solutions such as positive thinking, therapy & counselling for mental health, natural healing solutions have a profound impact on our overall mental well-being. Healing your gut, liver & microbiome is essential for overall brain health.
The connection between our brain & digestive system(gut) has many names:
- Microbiota-gut-brain axis
- Microbiota-gut-brain connection
- Brain-gut-microbiome axis
Each of these names explains gut-brain connection. Between our gut is our microbiome & central nervous system( brain). The interaction between our gut & brain is not unidirectional but bi-directional. This two way communication is working towards maintaining balance & our health. In fact, the brain & gut are connected through the vagus nerve. It runs from the brain, through the heart, lungs, liver, spleen, kidneys & down to intestines.
Feeling low or unable to think clearly is a clear indication that there is some imbalance in our system. Our gut acts as a second brain & houses millions of neurons. Undoubtedly, your toilet habits have an impact on your mood. Intrinsic nervous system, part of autonomic nervous system, regulates functioning of gastrointestinal tract. This nervous system is home to 500 million neurons in & around the gut.
And while this number is staggering, it’s only 0.5% of our body’s total neuron estimate. With your brain comprising perhaps 100 billion! And a lowly 100 million in our spinal column. Our body’s nerve cells are always talking to each other.
Let us discuss how the signalling mechanism between brain & gut microbiome works.
There are two mechanisms through which our gut microbiome influences our brain & central nervous system:
- Neuroimmune signalling pathways( immune & CNS connection)
- Neuroendocrine signalling pathways( hormone & CNS connection)
Both of these pathways involve the vagus nerve. Both need several microbial metabolites including short chain fatty acids(SCFA), tryptophan & secondary bile acids.
These molecules then stimulate signals through interactions with specialised cells in epithelial lining. Another Gut Brain Axis mechanisms for short chain fatty acids & other metabolites through direct transport- across intestinal barrier & blood brain barrier. By producing neuroactive molecules such as dopamine, norepinephrine, gamma-aminobutyric acid and 5-HT (serotonin), our gut microbiome can activate CNS signalling. Before we explain this in detail, let us talk about vagus nerve
Vagus nerve- the major building block of gut-brain connection is a very long nerve & runs from brain-stem to our gut(colon). It undertakes following functions:
- Internal organ sensory information signals-from neck, chest, abdomen including your gut.
- Carries information from the heart including sensors that detect oxygen in blood & blood pressure level.
- Controls muscle critical in swallowing & speaking
- Plays a significant role in the parasympathetic nervous system. Including “rest and digest” enteric nervous system functions and slowing of heart rate.
- Plays an important role in taste sensation
Now we can easily visualise how the vagus nerve plays an important role in our digestive process & hence our gut has a profound impact on various other necessary functions of our body. To summarise, the vagus nerve acts as information pathways from & to the gut. It carries information from specialised cells, microbial metabolites & other organ systems. It also influences many critical functions such as digestion & associated intestinal epithelial immune & hormone signalling pathways
Intestinal barrier
Our intestinal barrier/lining is a single thick layer. Its protective immune boosting mucus layer is what stands between you & your food( and poo). Its strength & foundation is key to your gut & overall holistic health. We have discussed the impact of leaky gut on our body in our earlier blog
Just remember, our gut lining acts as a gatekeeper. Daily you expose your gut lining to various foods & drinks & it boils down to your intestinal lining to figure out who is welcome. Millions of gut lining neurons regularly pass on information to the vagus nerve. However, it is important to understand gut microbes, stress & inflammation can change your gut lining permeability & the amount of information passing through the intestinal barrier. The amount of information reaching from brain to gut & vice versa is variable & depends upon what you feed your bacteria.
Stress causes leaky gut through,
- Impact on epithelial permeability
- Changes in intestinal mucosal layer
Which results in movement of gut bacteria & metabolites through gut lining.
Our intestinal barrier plays a key role in gut-brain connection.
Similar to intestinal barrier/lining which is a natural barrier to signalling within the gut, so is blood-brain barrier. It regulates molecular traffic between your blood & your cerebrospinal fluid, critical fluid surrounding your brain & spinal cord. This barrier is also impacted by stress, inflammation & gut microbes & impact the information passing through.
Let us discuss gut signalling mechanisms that acts as major driving force for gut-brain-microbiome connection.
Neuroendocrine & enteroendocrine signalling pathways wherein gut microbes communicate with endocrine cells in the gut. There are at least 12 different types of endocrine cells.
Besides, the short chain fatty acids are another important signalling molecule which are microbial fermentation products from resistant starch. We have discussed the role of butyrate, propionate & acetate in regulating food intake, appetite & digestion in our earlier blog. This is done through EEC cells. These cells are great examples of brain-gut communication. The neurotransmitter serotonin- the happiness enabler is produced by EEC in our gut. This accounts for 90% of serotonin production in the body. Serotonin regulates functions such as mood, pain responses, behaviour & cognitive function. SCFA & secondary bile acids promote large function of serotonin release.
Essential amino acid tryptophan is a precursor to serotonin & many other neuroendocrine metabolites & in fact regulates serotonin.
Let us also through light on other neurotransmitters produced in the gut
- Gamma-amino butyric acid is the main CNS inhibitory neurotransmitter & body’s natural relexant. GABA is produced by some gut bacteria such as Bacteroides, Parabacteroides, Eubacterium, Bifidobacterium and Escherichia.
- Acetylcholine: This normally enters our body through Sauerkraut. Acetylcholine is an abundant neurotransmitter found in the body. It is crucial for muscle contraction, memory, attention and cognition. Those suffering from Alzheimer’s disease show severe depletion of acetylcholine.
- Melatonin: Also known as sleep hormone, this is produced by ECC in the gut.Melatonin is also produced in the pineal gland. It drives our circadian rhythm and sleep-wake cycles once released into the bloodstream. Digestion and food intake are also regulated by this important endocrine hormone.
Gut & Mental health are closely related & there are a number of conditions linked with them. Inflammation & gut health are key in mental health. Anxiety, stress & depression are closely associated with occurrence of chronic inflammation & diseases such as IBD. Chronic inflammation due to stress & depression can lead to microbial changes & make our immune system release cortisol which directly makes our gut microbiome to shut down the digestive system leading to diseases such as bowel syndrome & IBD. Around 15% to 20% population suffer from IBS. Most sufferers experience decreased quality of life. In fact depression & anxiety are found common in people suffering from IBS. People suffering from IBS have a different microbial ecosystem as compared to those having a healthy life.
To sum up, Our Gut-microbiome has a deep effect on our brains. It influences everything we thought was ‘all in our heads’. From mood and behaviour to mental illnesses. Evaluating the interaction between our brain & gut microbiome can help us overcome risk of lifestyle diseases. To unlock & decode your gut microbiome composition, sign up for our health intelligence services here.
