Connection Between Brain And Gut – Gut Brain Axis

Updated on & Medically Reviewed by Dr Lalitha

It has been established that there is a connection between the brain (central nervous system) and the gut (enteric nervous system) which is bidirectional and is known as the GUT BRAIN AXIS.

The brain has a direct effect on the stomach and the intestines which are vice versa too. For example, as you start having food by your mouth, the juices in the stomach are produced before the food enters your stomach. Same way if there is any discomfort/pain in the stomach or intestine the signals reach the brain and cause a change in the behavior/mood.

The gut flora consisting of microorganisms are also found to influence the interactions between the gut and the brain in the Gut-Brain Axis, making it important for maintaining a healthy gut flora for healthy digestion, mood, and sleep, which are essential for a healthy life.

How are Gut and Brain Connected in the Gut-Brain Axis?

The Gut-Brain Axis is a bidirectional link between the higher brain that is the central nervous system and the nervous system of the Gut, called the Enteric nervous system. The understanding of the Gut-Brain axis has revolutionized the understanding of gut problems related to mood and health and helps us to treat bowel problems in a better way.

Both these nervous systems talk to each other via multiple mediators like hormones, neurotransmitters, cytokines, chemokines, etc. Due to this connection between the brain and the gut, gut problems can lead to mental disturbances and mental health problems can lead to gut problems.

What is Gut’s Second Brain?

  • The enteric nervous system (network of nerves in the gut wall) present in the walls of the digestive system is known as the gut’s “second brain”, which sends signals from the gut to the higher brain.
  • The second brain does functions, more than just processing the food we eat.
  • The enteric nervous system is part of the autonomic nervous system which is a network of peripheral nerves, that control the functions like digestion, absorption of nutrients, intestinal movement, etc.
  • Gut problems are communicated by its second brain to the higher brain resulting in behavior problems and psychological disorders.

What is the Role of Gut microbes (Good Bacteria in the Gut)?

The gut microbiome (good bacterial flora in the gut) consists of a lot of microorganisms present throughout the gastrointestinal tract, that play a significant role in the Gut-Brain Axis.

  • The gut microbiome sends signals to the brain through the Gut-Brain Axis involving the endocrine and the immune responses, which affect behavior, mood, and digestive health.
  • Certain species of gut bacteria influence the nervous system differently during stressful conditions, and vice versa stress response in the body can affect the gut bacteria.
  • Some of the gut bacteria are capable of producing neurotransmitters found in the brain.
  • Neurotransmitters primarily act locally on the gut, activating the enteric/gut nervous system.
  • An increase in neurotransmitters like serotonin in the brain is important in regulating mood, appetite, and gastrointestinal functions.
  • So if gut microbes are healthy they can alter the brain function and help to manage Gut-Brain Axis disorders such as irritable bowel syndrome, depression, and autism.
  • Gut microbes can be affected by many factors such as mode of birth, delivery, diet, antibiotics and other drugs, lifestyle changes like smoking and alcohol consumption.

How Does Gut-Brain Axis Respond to Mood & Stress?

The Gut-Brain Axis consists of bidirectional signaling between the gut and the brain which is regulated at neural, hormonal, and immunological levels, which is essential for vital homeostasis in the body.

  • Health & good mood –  The Gut-Brain Axis response will respond to a normal, healthy central nervous system function, normal gut physiology such as normal gut function and gut flora, with normal physiological levels of inflammatory cells/mediators and the normal gut microbiome.
  • Stress/ Disease condition – The Gut-Brain Axis has to respond to altered nervous system signals, abnormal gut function, increased levels of inflammatory cells/ mediators, disturbance in gut flora or bad bacteria (intestinal dysbiosis), and hormonal imbalances. There will be an alteration in behavior, cognition, emotion, sleep, and pain as a result of response to stress or disease.

What Happens When You Eat Something Bad?

When you eat something bad your body systems respond as if, you need help to save you from this situation.

  • Emotional signals from the gut are sent from the enteric system to the higher brain.
  • Then there will be an immune and stress response in the body involving the Gut-Brain Axis.
  • Gastrointestinal disturbances occur which are communicated to the brain and the mood is affected leading to behavior changes.
  • The immune system in the body tries to expel foreign substances or harmful toxins.
  • The gut bacteria gets affected and bad bacteria start to thrive causing gastrointestinal disturbances.

[ Also Read: Healthy Foods to Increase Immunity ]

Is Healthy Gut Flora/Microbiome Necessary for Gut Health?

  • Intestinal microbes help to maintain bowel health and motility.
  • Good bacteria decrease gut inflammation and prevent health problems such as constipation, diarrhea, or motility disorders.
  • They help to reduce functional gastrointestinal disorders like irritable bowel syndrome which have a stress-related or psychiatric component.
  • The immune response can be restored and immune functions of B and T cells can be improved.
  • Healthy gut flora is essential to fight against disease, inflammation, stress, and an unhealthy diet.

How are Probiotics Useful for Gut-Brain Axis Disorders?

Probiotics are microorganisms, usually, bacteria are known as good bacteria and are useful to maintain a healthy gut.

  • Probiotics such as Lactobacilli, Bifidobacterium, Saccharomyces, etc are usually widely used to restore healthy gut flora and reduce bad bacteria.
  • The probiotic treatment promotes intestinal health and improves behavior problems caused due to stress-related conditions.
  • Probiotics aid in the absorption of essential nutrients in the body from the intestines.
  • Probiotics can reduce bloating or gas and help in the proper digestion of food.

The connection between the gut and the brain is important and has been understood through the GUT BRAIN AXIS. The gut microbiome helps in the bidirectional interactions between the gut and the nervous system.

Ideal gut bacterial flora can lead to the adequate functioning of the bowel which helps keep the mind happy and vice versa.

Probiotics help to maintain healthy gut flora/microbiome, preventing many gut and mood disorders, gastrointestinal infections, and motility disorders. 

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