“The gut is the second brain”, “the brain-gut connection”. Have you come across these terms? Possibly yes and… quite a lot. This relationship has gained a lot of focus in the last few years. You can find such connections almost anywhere and in a similar format. You may begin to feel accustomed to such terms, but do you understand the relationship?
If you are not entirely certain, this blog might help answer your questions in a simpler format.
What is the Gut-Brain Axis?
It is bidirectional communication through different channels within our body with the help of different systems. We might even say that this communication is one of the most frequent communications within the body, mainly mediated by the microbiome.
The Microbiome
Microbiome refers to the single-celled organisms (microbes) living in our guts, such as bacteria, and fungi. In a healthy adult, good microbes are superior in number to harmful microbes. These organisms help food digestion, the functioning of the gut, and more.
But How?
Currently, the dynamics of how the gut and the microbiome affect the brain have not unfolded completely. However, thanks to the increased attention diverted to this area of research, there is an increased number of published papers each year. Based on recent research, the gut and its microbiomes exert their effects together mainly through four pathways, which are :
1. Neurological Pathway
2. Endocrine Pathway,
3. Metabolic Pathway
4. Immune Pathway
1. Neurological Pathway
This communication channel happens through the nervous system and its related components. In neural communication, the gut microbiome communicates with neural cells that directly reach the brain. One of these nerves is the Vagus Nerve, responsible for digestion, heart rate, and calming the body. When it is actively working, it allows messages to be sent to the brain. Neurotransmitters enable the messages to be delivered when used or activated; just like sending a message through the phone via the ‘send’ button. Moreover, the gut microbiome also affects the nerve messages within the gut itself.
2. Endocrine Pathway
This is the line of communication regarding hormonal activity and its feedback. So, how does the gut affect the brain through this channel? Essentially, the microbiome has the power to modify the availability of nutritional molecules. Depending on the bacteria’s effect, this can activate certain mood hormones in the brain. For instance, this microbiome can lead to increased availability of a molecule that can cause stress hormones like corticosteroids from the brain. As a result of that activity, the person starts to experience stress physically, mentally, or both.
3. Metabolic Pathway
The Metabolic Pathway is the pathway for chemical molecules that emerge as a result of enzymic or digestive reactions. Here, chemical molecules are equal to the components that remain from bacteria after they help food digestion. Those components are called metabolites and are related to how the guts affect the brain. Among the
metabolites, there are two important bacteria metabolites in the gut: short-chain fatty acids (SCFA) and lipopolysaccharide (LPS). These are produced in the gut, by the microbiome during food digestion.
SCFA
This helps protect the brain from inflammation and behaves as a brain hormone (influencing our mood). SCFA can enter through the brain-blood barrier; a tissue acting as a gatekeeper to protect the brain against any harmful particles. When SCFAs enter into brain area, they act like the white blood cells in our body, by destroying damaging materials. This protects the brain against developing brain diseases like Alzheimer’s. Moreover, it regulates the production of serotonin i.e the happiness hormone in the gut, where 95% of it is produced.
LPS
Unlike SCFA, this damages the gut line, and consequently the brain. It can leak into the body’s blood system, resulting in the production of antibodies to fight it. Producing antibodies means having a special force of police aiming to catch one specific person. This issue mentioned is also known as a leaky gut syndrome. Studies also show that people with depression have a higher likelihood of an increase in antibodies against LPS.
4. Immune Pathway
The Immune Pathway incorporates the communication between cells, tissues, and organs like white blood cells and tonsils, against pathogens, and infections. The gut microbiota is one of the parts of the system which influences inflammation metabolism within the GI tract. For instance, in IBS, an unhealthy microbiome causes an immune reaction in the gut tissue, causing activation of painful feelings in the guts. This impairs the regulation of the intestines in people with IBS.
Tips For You
1. Do something to release your stress
2. Add probiotics and prebiotics to your diet
3. Prefer unprocessed and healthy meals and snacks over junk and unhealthy foods 4. Do not use unnecessary medications unless prescribed by your doctor
Thus, the gut affects the brain either positively or negatively through the help of the microbiome (and the four main pathways). Which depends on how well you take care of gut health.
If you think that you can benefit from professional support on this issue you can reach here.
Eda Hayrula is an intern working under Willingness with a bachelor’s degree in Psychology. Her interests in Psychology are gastrointestinal disorders, coping with stress, psychosomatic disorders, and trauma.
References:
Appleton J. (2018). The Gut-Brain Axis: Influence of Microbiota on Mood and Mental Health. Integrative medicine (Encinitas, Calif.), 17(4), 28–32.
The microbiome. The Nutrition Source. (2022, July 25). Retrieved August 5, 2022, from https://www.hsph.harvard.edu/nutritionsource/microbiome/ #:~:text=The%20microbiome%20consists%20of%20microbes,symbiotic%20micro biota%20coexist%20without%20problems.
Chakrabarti, A., Geurts, L., Hoyles, L., Iozzo, P., Kraneveld, A. D., La Fata, G., Miani, M., Patterson, E., Pot, B., Shortt, C., & Vauzour, D. (2022). The microbiota-gut-brain axis: pathways to better brain health. Perspectives on what we know, what we need to investigate and how to put knowledge into practice. Cellular and molecular life sciences : CMLS, 79(2), 80. https://doi.org/10.1007/s00018-021-04060-w