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The gut-brain axis - the bi-directional communication channel


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The human gut contains a complex ecosystem of over 10 trillion microorganisms, including bacteria, fungi, yeasts, and protozoa, known as the gut microbiota. This tiny but mighty world of living organisms operates like an organ, generating essential nutrients and metabolites that play a critical role in overall health and well-being (1).

Did you know that gut microbiota may also impact brain function? 

Is there a potential link between the "gut world" and the "brain world"?

Moreover, is it possible that the gut-brain axis is the underlying cause of mood changes in children?


The Gut-Brain Axis – the bidirectional communication channel


The gut-brain axis also known as GBA refers to the bidirectional communication between the central nervous system and the enteric nervous system in the gut. It links the emotional and cognitive centers of the brain with peripheral intestinal functions (2).  


The interaction between microbiota and GBA occurs through signaling from gut-microbiota to brain and from brain to gut microbiota by means of multiple channels including neural, endocrine, immune, and humoral links. The bidirectional communication can affect brain chemistry, stress response, anxiety, and memory function. The working of gut-brain axis is bidirectional, meaning the nervous system can also affect the composition of the gut microbiota (2).


Impact of microbiota on mood, brain development and mental health


According to recent clinical data, the gut microbiota plays a crucial role in bidirectional communication. These bacteria can produce neurotransmitters like serotonin that can affect human behavior, emotions, and decision-making. The studies indicate that gut bacteria can also affect brain development, especially in preschool children, and can influence cognitive, social, and emotional behavior (3).


Metabolic pathway


Gut bacteria produce short-chain fatty acids and lipopolysaccharides. The short-chain fatty acids can cross the blood-brain barrier and regulate microglia homoeostasis, which is important for proper brain development and behavior. Lipopolysaccharides can enter the systemic circulation and affect mood. Disruptions in short-chain fatty acid metabolism have been linked to autism (4).


Hormonal pathway


The gut bacteria can affect the gut-brain axis by altering the release of important hormones like galanin which is involved in important brain functions like sleep regulation, mood, and stress response (4).


Neurological pathway


The nervous system in our gut influences the release of certain molecules like serotonin, GABA, and histamine, which can affect our mood and immune system (4).


Immunologic pathway


The gut microbiome can cause inflammation in the GI tract, which affects the immune system and can lead to conditions such as irritable bowel syndrome (IBS). IBS can cause gut pain, affect the gut-brain connection, and disrupt normal gut functions like motility and secretion (4).


Disturbances in gut microbiota can impact infant’s health


The establishment of a stable gut microbiota generally accompanies two big transitions in infancy. 1st transition happens soon after birth with the dominance of bifidobacterium. 2nd transition happens during the weaning period with the domination of phyla Bacteroidetes and Firmicutes. Post this period the gut microbiota is dominated by enterophytes. The friendly bacteria have a greater impact on the infant’s digestive tract and immune system. Dysbiosis is a mechanism where the symbiotic relationship between the host and gut microbiota is altered (5). 


Alteration of gut microbiota affects the production of neurotransmitters and metabolites including tryptophan, cortisol, and serotonin. Dysbiosis is highly associated with mood disorders in infants and children (5). Dysbiosis is also linked with multiple diseases in infants such as asthma, IBD, and Crohn’s disease (6). 


Reinforcing the gut microbiome power 


Babies are born with an immature immune system and depend on the microbial colonization process for better immune function and development. Breast milk provides probiotics and nutrients favoring the growth of bifidobacteria, which ferment milk oligosaccharides to shape the baby’s gut microbiome power. Human milk is also rich in human milk oligosaccharides (HMOs) which play an important role in shaping microbiota. They act as prebiotic allowing the growth of beneficial bacteria while preventing the colonization of harmful pathogens (6).

Reinforcing the gut microbiome power requires healthy nutrition with a blend of HMOs, prebiotics, probiotics, protein, tryptophan, and other essential nutrients. Right nutrition at the right time has a beneficial impact on infants’ growth and development (7).  

About the Author


Ms. Disha Goyal is a medical content writer with expertise in handling campaigns related to health & wellness and nutrition. Disha provides medical content support to organizations specializing in health and fitness. Some of her recent projects included topics such as food & nutrition, diabetes reversal, gut health, hormonal health, reproductive health, fitness, yoga, chronic medical issues, and others.


References


  1. Brett BE, de Weerth C. The microbiota-gut-brain axis: A promising avenue to foster healthy developmental outcomes. Dev Psychobiol. 2019 Jul;61(5):772-782. 

  2. Carabotti M, Scirocco A, Maselli MA, et al. The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Ann Gastroenterol. 2015 Apr-Jun;28(2):203-209.

  3. Liu YW et al. Effects of Lactobacillus plantarum PS128 on Children with Autism Spectrum Disorder in Taiwan: A Randomized, Double-Blind, Placebo-Controlled Trial. Nutrients. 2019 Apr 11;11(4):820.

  4. Appleton J. The Gut-Brain Axis: Influence of Microbiota on Mood and Mental Health. Integr Med (Encinitas). 2018 Aug; 17(4): 28–32.

  5. Tanaka M, Nakayama J. Development of the gut microbiota in infancy and its impact on health in later life. Allergol Int. 2017;66(4):515-522.

  6. Moore RE, Townsend SD. Temporal development of the infant gut microbiome. Open Biol. 2019;9(9):190128.

  7. Gibson GR, Hutkins R, Sanders ME, et al. Expert consensus document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics. Nat Rev Gastroenterol Hepatol. 2017;14(8):491-502.

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