Mind Your Gut: The Surprising Brain-Body Connection

Written by: Saina Gupta (2nd year)department of Applied Psychology

Microbial Messages: Mood-Altering Molecules

Have you ever had a bad ‘gut feeling’ about something or someone? Or maybe felt butterflies in your stomach? There is a biological reason for this phenomenon. Our brain communicates with all of our body through nerves (our nervous system). Therefore, more information passes between our brain and our gut than any other body system. Thus, it can be said that the expression ‘gut feeling’ is more than just a quirky saying.

Our gut includes our gastrointestinal system, i.e. our stomach, intestines and colon. They digest and absorb nutrients from our food and excrete waste. They are based around the mucous lining on the inner walls. The gut is not just a digestive organ—it is a complex, dynamic ecosystem home to trillions of microbes and millions of microbial genes, vastly outnumbering our own genetic material. A biome is a distinct ecosystem characterized by its environment and its inhabitants, and our gut- inside our intestines- is in fact a miniature biome, populated by trillions of microscopic organisms. These microorganisms include over a thousand species of bacteria, as well as viruses, fungi and parasites, and are collectively referred to as the ‘gut microbiome’. We have some gut microbiota in our stomach and small intestine, but most of them are in our large intestine (colon).

Our brains and digestive systems have evolved together to help us survive. Our food habits are crucial to our overall health, and it has also varied a lot throughout history, depending on what was available. Our brain and gut needed to stay in close contact to make sure everything was in order. If we ate something wrong, or needed to put the brake on digestion, we had to have a good alarm system in place. This alarm system includes the emotional part of our brains. After a physical injury, our emotional brain kicks in to help us remember to avoid that injury in the future. It can make physical sensations in our gut seem more intense and can also raise our stress levels and our emotional response. This feedback loop is especially strong between the brain and the gut.

Our Enteric Nervous System (ENS) is the neural network that operates within our GastroIntestinal (GI) tract and controls its digestive functions. With more than 500 million neurons, it’s the most complex neural network outside of the brain. It’s also unique in that it can operate somewhat independently from our brain and central nervous system. This has led some scientists to refer to it as a “second brain”. The enteric nervous system is a special division of the autonomic nervous system, which governs the automatic functions of our internal organs. It operates as part of the overall autonomic nervous system, but also, and more importantly, on its own. It communicates directly with the brain through the vagus nerve, creating a bidirectional signalling pathway known as the gut-brain axis. It regulates the normal function of the human body, involving the neural, endocrine and immune systems. These influence mood, sleep, appetite, pain sensitivity, and overall well-being.

A healthy gut

Our gut microbiome can be affected by stress, too little sleep,lack of physical activity, eating too many ultra-processed foods, smoking and drinking alcohol, and taking antibiotics.

Some signs that you may have poor gut health include digestive symptoms such as gas, bloating, constipation, diarrhoea and heartburn; sleep disturbances or fatigue; mood/emotional state – such as high stress, low mood or anxiety; high frequency of infectious illnesses – such as the common cold.

Maintaining a stable gut environment or ‘Gut homeostasis’ is crucial for overall health. A balanced gut microbiome consists of a diverse range of beneficial bacteria that contribute to immune system regulation, efficient digestion, and protection against harmful pathogens. Dysbiosis is a disruption of gut homeostasis. It is not only a loss of beneficial bacteria but also an overgrowth of harmful microbes. It can lead to increased gut permeability, immune activation, neuroinflammation and changes in the blood–brain barrier.

Dysbiosis means a loss or deficit of beneficial bacteria; overgrowth of potentially pathogenic (bad) bacteria and loss of overall bacterial diversity.

People with a range of neurological and psychological disorders, including depression, schizophrenia, autism, Parkinson’s disease and multiple sclerosis, have been reported to show changes in the composition of the gut microbiota in comparison to healthy individuals.

The Belly and The Brain

The bidirectional relationship between the gut and brain means they constantly influence each other. The brain influences gut functions via the Hypothalamic–Pituitary–Adrenal (HPA) axis and the Autonomic Nervous System (ANS). For instance, norepinephrine is produced by the brain in response to stress. It has been shown to promote the growth of harmful bacteria in our gut, making the body more susceptible to gut issues.

Simultaneously, gut microbiota influences release of substances like neurotransmitters (brain messengers), gut hormones, short-chain fatty acids, bile acids, and even 90% of our body’s serotonin—a key chemical for mood and emotions. Gut-derived serotonin can travel to the brain and affect our emotional state, demonstrating the gut's direct influence on mental health. Gut bacteria play a role in synthesizing dopamine. For example, after eating a delicious meal, the sensation of pleasure we feel is partially due to dopamine produced with the help of gut bacteria.

Our brain triggers a stress response in stressful situations such as after a breakup, or during exams. It releases cortisol and norepinephrine, hormones which disturb our gut microbiota, making our digestive system more sensitive. People often start relying on comfort foods during such times, which can cause indigestion, bloating and cramps. The distressed gut then sends signals back to our brain via the vagus nerve, worsening our mood and anxiety. This creates a vicious cycle—our brain affects our gut, and our gut affects our brain.

Gut-influenced behaviour

The idea that ‘All disease begins in the gut’, attributed to Hippocrates, resonates more than ever in modern science. Gut microbiome dysbiosis has been increasingly associated with several psychological disorders. People with anxiety often have an imbalance in their gut bacteria, showing reduced microbial diversity and a lower abundance of beneficial, short-chain fatty acid-producing bacteria. Instead, there is an increase in potentially harmful bacteria which further influence the production of important neurotransmitters like dopamine, serotonin and GABA, which regulate moods. Chronic treatment with a probiotic containing Lactobacillus rhamnosus JB-1 can reduce anxiety and depression related behaviours.

Dysbiosis can lead to issues with attention and cognitive function, which may make Attention Deficit Hyperactivity Disorder (ADHD) symptoms worse. Inflammatory chemicals can disrupt brain areas responsible for focus and impulse control. Schizophrenic individuals often have gut problems, including a weak gut barrier, bacteria moving into the bloodstream, and frequent digestive issues. In children with autism, gut metabolites differ significantly from those in neurotypical individuals. For instance, levels of Short-Chain Fatty Acids (SCFAs) are typically lower in autistic children. Certain prebiotics, like wheat fibre, have shown potential therapeutic benefits by reducing harmful bacteria and boosting beneficial ones.

Ways to keep the gut happy

➢ Diet: To support a healthy gut, we should aim for a diverse, fibre-rich, and minimally processed diet. Including plenty of high-fibre foods like whole grains, fruits, vegetables, legumes, and nuts feeds beneficial gut bacteria and promotes the production of SCFAs that reduce inflammation and strengthens the gut lining.A diet composed of highly processed food and elevated levels of saturated fat and sugar increases the relative abundance of pro-inflammatory bacteria and leads to increased risk for metabolic and inflammatory diseases. Add fermented foods such as curd (yogurt), buttermilk (chaas), idli, dosa, dhokla, and traditional pickles to boost the intake of natural probiotics. Incorporating natural prebiotic-rich foods like garlic, onions, bananas, and asparagus, along with polyphenol-rich options such as berries, green tea, dark chocolate, and olive oil enhances microbial diversity.

➢ Ayurvedic medicine: Ancient wisdom places primary importance on digestive health for both physical and mental well-being. A balanced gut is crucial for proper digestion, assimilation, and elimination, directly impacting mental clarity and emotional stability. Treatment options include a combination of dietary therapy, lifestyle adjustments, herbal formulas, and acupuncture. Yoga, an integral part of Ayurveda, offers numerous benefits for the gut-brain axis by promoting relaxation, reducing stress, and enhancing digestive function.

➢ Probiotics & Prebiotics : Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the body. For example, taking a daily probiotic supplement like yogurt or kefir containing lactobacillus and bifidobacterium can help balance the gut microbiome and improve mental clarity by increasing Gamma Aminobutyric Acid (GABA) production in the gut and affects several Central Nervous System (CNS) conditions, such as major depressive disorder, stress, ADHD, and Autism Spectrum Disorders (ASD). Probiotic use may reduce cortisol levels, lower perceived stress, decrease emotional brain reactivity, and even reduce negative thought patterns like rumination and aggression (Sarkar et al., 2016). Prebiotics are non-digestible fibres that feed beneficial bacteria. Foods like onions, garlic, and bananas are rich in prebiotics and should be included in the diet to support gut health.

➢ Psychotherapy: Psychotherapeutic interventions involve psychological techniques to improve mental health, reduce stress and improve gut–brain communication. Cognitive-behavioural therapy (CBT) can help individuals manage gut-related anxiety by changing thought patterns related to digestive discomfort. It can help reduce symptoms by using relaxation techniques and guided imagery to alter gut-brain interactions. Introducing stress management techniques such as yoga or deep breathing can calm the gut and reduce anxiety levels by reducing cortisol and adrenaline, which can otherwise disrupt gut function and exacerbate anxiety.

Conclusion

Improving the gut microbiota using probiotics, prebiotics, a healthy diet, faecal transplants and lifestyle changes could become a powerful way to support both mental and digestive health in the future. The gut-brain axis is a dynamic field with ongoing research, theories, and emerging concepts. By staying informed about these developments, individuals can make more informed choices to support their gut-brain health through diet, lifestyle, and therapeutic interventions. Understanding and supporting the gut-brain axis can promote both mental clarity and emotional resilience, as well as, enhanced overall health and well-being.

References

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Written by:

Saina Gupta

Edited by:

Patmateertha (Associate editor)

Vasudha Sharma (Deputy Content Team Coordinator )