The Gut-Brain Axis: How Bacteria Affect Mood

We all get that “gut feeling” from time to time. Have you ever wondered why a gut feeling feels so physical? It is not just a metaphor.

After carrying out various experiments and studies, scientists have found that a complex two-way communication network exists between your gut (digestive system) and your brain.

This network is known as the gut-brain axis. They have also found that your gut and your mind (brain) are “talking” constantly.

These “conversations” come from trillions of microbes that are the residents of the gut microbiome and they are responsible for doing far more than just digesting the food you eat.

The microbes in your gut produce neurotransmitters such as serotonin and dopamine.

These neurotransmitters affect your mood, stress levels, emotions and mental clarity.

In other words, the state of your gut determines how happy you are, your brain-function, how you handle stress, the way you think and your whole temperament.

The gut-brain axis links the central nervous system (brain/spinal cord) with the enteric nervous system (gut-brain).

It uses neural (vagus nerve), endocrine (hormones), immune, and metabolic pathways to carry out its functions.

In this blog, the gut-brain axis is explained in detail.

Here, you will discover the science behind the link between your gut-bacterial health and your mood; and the reason why a happy gut is necessary for having a balanced mind.                

Key Elements and Mechanisms of the Gut-Brain Axis

1. Bidirectional Communication: The git-brain axis engages in bidirectional communication. Signals are exchanged between the brain and the gut.

The state that the brain is in determines gut-function (secretions, permeability, motility etc.), while the condition of the gut affects a person’s mood, cognition, and stress-tolerating ability.

2. Vagus Nerve: The vagus nerve is the longest, most extensive nerve in the autonomic nervous system that connects the brain to other vital organs (heart, lungs, gut etc.).

Because of this connectivity, direct and rapid signalling is possible between the two systems.

3. Enteric Nervous System (ENS): The Enteric Nervous System is a complex system that has about 200-600 million neurons lining the gastrointestinal tract, right from the esophagus to the rectum.

It is known as the “second brain”. The ENS has the ability to control digestion and immune responses independently.

4. Immune & Endocrine Systems: The gut-brain axis and stress are interrelated.

It is a known fact that about 80% of the immune system resides in the gut. And it responds according to changes in a person’s gut-health.

The hypothalamus-pituitary-adrenal (HPA) axis is responsible for managing stress and releasing cortisol; both of these factors impact a person’s gut health.

5. Gut Microbiota: Microbes in the gut produce neuroactive compounds, such as neurotransmitters (serotonin, dopamine) and metabolites (short-chain fatty acids).

These neuroactive compounds are responsible for the state of your brain chemistry.

And that is how a person’s gut-brain axis and mental health are connected.  

How does gut bacteria affect your mood?

1. Neurotransmitter Production: It has already been established that gut bacteria produces neurotransmitters.

In fact, as many as 90% of the body’s serotonin, dopamine and GABA are produced in the gut.

These neurotransmitters are in charge of regulating a person’s mood and sleep. They are also responsible for controlling feelings such as fear and anxiety.

2. Immune System Modulation: When there's a disbalance in the microbiome, it can lead to the inflammation of the gut.

When that happens, the immune system gets triggered and releases compounds that impact brain-signaling and lowers the mood.

3. Metabolite Production: Bacteria in the gut breaks down fibre. As a result, short-chain fatty acids (SCFAs), such as butyrate, are produced.

Butyrate is incredibly important for maintaining the blood-brain barrier and the regulation of neuroinflammation.

A lack of butyrate can cause anxiety and depression in a person.

4. Stress Response (HPA Axis): A person’s gut bacteria influences the hypothalamic-pituitary-adrenal (HPA) axis.

The HPA oversees the regulation of stress hormones such as cortisol.

When a person has a healthy microbiome, it helps in stress-management. An unhealthy gut can make a person have a high-stress response.

A high-stress response is the body’s fight or flight response to perceived danger.

When this high-stress response stays in active mode constantly, it can lead to a host of mental health issues.

Those mental health issues include anxiety, irritability, trouble concentrating, feeling overwhelmed, and depression.

Things you can do to support the Gut-Brain Axis

1. Dietary Changes: To make sure that the beneficial bacteria in the gut are thriving, consuming foods with high-fibre, prebiotics and probiotics is necessary.

2. Lifestyle Management: If you want to have a healthy microbiome, you need to follow certain lifestyle habits.

Those habits include getting enough sleep (7-9 hours/night), exercising regularly (walking, swimming, cardio etc.), reducing stress (by meditating).

3. Probiotics: There are certain probiotics that may help alleviate some mental health issues such as depression and anxiety.

It can be done by restoring balance to the gut microbiome.

Gut-Brain Axis FAQs

How can I improve my gut-brain axis?

The elements that influence the state of the gut-brain axis might seem simple enough but it is not always easy to adhere to them.

To maintain a healthy gut-brain axis, you need to nourish the gut microbiome and keep your nervous system calm.

To achieve those goals, you would need to follow a certain lifestyle and keep stress at bay.

And what sort of lifestyle should it be?

The kind where you need to eat foods with high-fiber, prebiotics and probiotics in them. For example, yogurt, legumes, fruits, nuts, vegetables and kimchi etc.

In addition to this, you would need to engage in some form of exercise on a daily basis; and get an adequate amount of sleep (7-9 hours/night).

What are the symptoms of gut-brain axis dysfunction?

The symptoms of gut-brain axis dysfunction include constipation, abdominal pain, constant bloating, diarrhea, brain fog, mood swings, fatigue, anxiety and depression.

A dysfunction in the gut-brain axis occurs when there’s a bidirectional breakdown between the central nervous system and the gastrointestinal tract.

When there’s a dysregulation of the gut-brain axis, it is manifested as chronic digestive issues along with neurological and/or immune-related distress.      

Is it true that 90% of serotonin is in the gut?

Yes. Almost 90% of the body's serotonin is produced in the gut. It influences gut immunity to a great extent.

Serotonin is a neurotransmitter (chemical messenger) that is responsible for transmitting messages among the cells of the body.

Serotonin is vital to the smooth functioning of various bodily processes such as healing of wounds, sleep-regulation, mood-regulation, maintaining bone health, cardiovascular health and the digestive system.

What foods boost the brain-gut axis?

If you want to boost the brain-gut axis, these are the foods you would need to consume fairly frequently— fruits, vegetables, nuts (walnuts etc.), green leafy vegetables, garlic, onion, leeks, yogurt, kimchi, seeds (flaxseeds etc.), and fatty fish (salmon, mackerel etc.)    

What is the 7 day gut reset?

The 7-day gut reset is a short-term plan that is helpful in improving digestion, reducing bloating and increasing energy levels.

It can be achieved through clean eating and making certain lifestyle changes.

If you want to reset and repair your gut, you need to avoid processed foods, reduce sugar and limit your alcohol intake.

And include foods that are rich in fibre, probiotics, and prebiotics in your daily-diet. You would also need to stay properly hydrated throughout the day.

How to heal your gut naturally?

Gut-brain connection research has proved that in order to heal your gut naturally, you need to pay attention to physical as well as mental elements of wellbeing.

Those elements include-

a. A healthy diet.

A healthy diet basically comprises foods rich in fibre, a wide range of plant-based foods (such as fruits, nuts, vegetables, and legumes), and fermented foods (such as yogurt and kimchi).

b. Regular exercise.

Indulge in some type of exercise atleast 4-5 times a week. It needs to be something that raises your heartbeat a few notches.

But it should not be so rigorous that you find it extremely difficult to breathe.

c. Proper sleep.

If you are an adult, you need atleast 7-9 hours of sleep every night.

d. Managing stress.

This can be done through yoga, meditation, art, talking to your loved ones etc. Everyday, spend a few minutes doing things that make you happy and feel relaxed.

e. Avoid junk food.

The kitchen or pantry is filled with processed foods in most homes; ready-to-eat snacks, chips, canned beans, and frozen delicacies that are easy to cook.

As much as you can, avoid consuming these foods that look okay and taste great, but have an adverse effect on your health in the long run.

f. Avoid sugar.

Sugars that are present in foods naturally are mostly okay, unless you are diabetic. Hence, you can eat sweet fruits and vegetables.

But the sugar you consume from processed food is incredibly harmful to your body and mind.

Most processed foods that may seem harmless— cakes, coffees, cookies, donuts, juices, chips, peanut butter, waffles, chocolates etc.— have added sugar in them.

These artificially added sugars create a host of health issues including heart diseases, acne, obesity, diabetes, fatty liver, depression, and cancer.  

What is the 3 to 3 poop rule?

The “3 to 3” poop rule denotes that a healthy bowel movement can range anywhere between three times a day and three times a week.

This is considered to be healthy and normal for adults. As many as 95-98% of healthy adults fall under this range of bowel movements.

When it comes to bowel movements, consistency is more important than a super-strict everyday routine.

What are the 4 R's of gut repair?

The 4 R’s of gut repair is a process that includes four steps. Those steps are—

a. Remove (Elimination of Irritants).

At this step, the goal is to reduce inflammation by removing substances that irritate the gut lining or disrupt the microbiome.

Those substances may include foods such as processed foods, excessive alcohol, foods with added sugars and certain allergens (dairy, gluten etc.)

It also includes reducing chronic stress and environmental toxins that can alter the condition of your gut.

b. Replace (Digestive Support).

This step puts emphasis on replacing those essential elements that are required by your body but are not being produced in the quantity that is needed to break down all the consumed food properly.

Those essential elements include hydrochloric acid (HCl), bile salts and digestive enzymes.

c. Reinoculate (Microbiome Balance).

The steps mentioned above would help in reducing inflammation of the gut interiors.

So, in this step, the focus is turned towards recreating  a diverse and healthy variety of microbes in the gut.

In order to do that, you would need to consume foods that fall under the category of probiotics and prebiotics.

Basically, make foods like curd, kimchi, asparagus, garlic, leeks, cucumbers, bananas, berries, nuts, leafy greens, oats, olive oil, broccoli, sauerkraut and onions a part of your regular diet.

d. Repair (Structural Healing).

At the final stage, you need to provide the specific nutrients that are required for healing the intestinal wall and strengthen structure efficiently.

And for that purpose, you need to consume foods that have Omega-3 Fatty Acids and L-Glutamine.

Make sure that your diet includes eggs, dairy products (yogurt, cheese, milk etc.), fish, chicken, nuts, beans, lentils, red cabbage, seeds, chickpeas and corn as these foods contain L-Glutamine.    

Foods you can consume to get the required amount of Omega-3 Fatty Acids are seeds & nuts (Flaxseed, walnuts, chia seeds, and hemp seeds), fatty fish (mackerel, sardines, salmon, herring and hilsa), plant oils (soyabean, canola and flaxseed), yogurt, eggs, and soya milk.

You also need to consume soothing herbs such as aloe vera, slippery elm and marshmallow root for repairing your gut.

How to detox your brain?

In order to detoxify your brain, you need to support its natural waste-removal system (the glymphatic system) by providing the things needed for it to work efficiently.

To optimize the brain’s glymphatic system, you need about 7-9 hours of proper sleep. You would also need to follow a healthy diet, limit alcohol intake, avoid processed foods, reduce stress-factors, reduce screen-time, exercise regularly and meditate.

Doing these things help in reducing inflammation, improving cognitive function and boosting overall brain function.