M.D. Medical Director, Psychiatrist
In recent years, scientists have discovered a fascinating connection between our gut and our brains. We’ve learned that the gut does much more than just digest food, it plays an important role in regulating our mood and cognition through what’s known as the gut-brain axis.
In this article, we explore what the gut microbiome is, how it forms, and how our gut can impact our mental well-being.
What is the gut microbiome?
The gut microbiome refers to the vast and diverse community of microorganisms that live in your digestive tract. These tiny organisms, like bacteria, archaea, viruses, and fungi, have evolved alongside humans for millions of years and play an important role in maintaining our overall health.
Believe it or not, the trillions of microbes living in your gut actually outnumber your human cells many times over. Collectively, they’re known as the gut microbiota and they help our body complete essential functions like:
- Breaking down complex carbohydrates and aiding digestion
- Producing vitamins and essential compounds that the body can’t make on its own
- Regulating the immune system and protecting our body against harmful pathogens
- Supporting metabolism and maintaining the integrity of your gut lining.
Where does the gut microbiome come from?
Just like we all have unique fingerprints, we all have completely unique gut microbiomes. Each person’s microbiome is shaped by their early life experiences and environment, forming an entirely unique signature that can’t be found anywhere else on earth. But where does it ‘come from’ exactly?
Well, unlike a genome, which is passed on from both parents, your gut microbiome is mostly maternal in origin, meaning it comes from your mother. The first microbes to colonize the gut are usually transferred from a biological mother during vaginal birth, skin-to-skin contact, and breastfeeding. This early exposure is often called ‘seeding’ and it helps build the foundation for a healthy gut ecosystem.
From there, a person’s microbiome continues to be influenced by their environment. Family members, pets, nature, and even the hospital room where you take your first breath can all contribute to this initial microbial ‘mosaic’.
By the time you’re two or three years old, your gut microbiome will typically stabilize into what’s called a steady state microbiome. This means that the dominant species in your gut will remain relatively unchanged into adulthood, although it will still be influenced by things like:
- Diet
- Antibiotic use
- Stress levels
- Exercise habits
- Sleep patterns.
Diet is especially important in shaping your gut bacteria – for example, changing your diet can alter your gut microbial populations in as little as 24 hours.
What factors imbalance your gut microbiome?
Most microbes in the gut are symbiotic, which means we help them and they help us. But when your microbiome becomes imbalanced, the relationship can be more dysbiotic. This means there’s less of the ‘good’ bacteria and more of the ‘harmful’ bacteria.
Some common triggers of dysbiosis include:
- Changes in diet, especially diets high in processed foods and low in fiber
- Chronic or acute stress
- Using antibiotics and other medications
- Environmental toxins or infections
- Poor sleep or irregular lifestyle habits.
Your gut lining has a specialized barrier that allows essential nutrients to pass into the bloodstream while keeping harmful bacteria, food particles, and metabolic byproducts inside the gut. Dysbiosis can make this barrier more permeable, which means bacteria and unwanted molecules can enter the bloodstream and cause inflammation in different systems of the body – including the brain. This is referred to as ‘leaky gut syndrome’.
Research has linked dysbiosis and increased intestinal permeability to a range of health concerns, including inflammatory bowel disease (IBD), diabetes, asthma, allergies, anxiety, depression, bipolar disorder, and neurodevelopmental disorders. Which brings us to the next section.
Learn More: How Diet and Exercise Affect Your Mental Health
What is the gut-brain axis?
The gut-brain axis is a bidirectional communication system that connects the emotional and cognitive centers of your brain with the physiological functions of the digestive system. It basically links the central nervous system (CNS), which includes the brain and spinal cord, with the enteric nervous system (ENS) housed within the gut, sometimes referred to as the body’s ‘second’ brain.
The ENS is a complex, mesh-like system embedded inside your gut lining. It contains between 200 to 600 million neurons and shares many of the same structural elements as the brain itself, including motor neurons, sensory neurons, and neurotransmitters. So what does all this mean?
You can essentially think of your gut as having its own brain. In fact, the ‘gut brain’ actually contains more of certain neurotransmitters (like serotonin) than your actual brain does. But instead of processing thoughts and emotions, the gut’s brain completes tasks like digesting food, absorbing nutrients, and regulating intestinal motility (moving contents through the digestive tract).
What’s really interesting is that the ENS can function independently of the brain, which means it takes care of digestion and gut function without any input from your brain. Most of the time, however, your gut and brain are in constant communication to maintain homeostasis, the body’s internal state of balance.
The role of the vagus nerve
The vagus nerve is one of the longest nerves in the body, extending from the brainstem all the way to the abdomen, connecting with key organs along the way. As the most direct link between the brain and gut, the vagus nerve acts as a two-way communication channel that allows for information to quickly move between the two regions.
The gut-brain axis also relies on endocrine (hormonal), immune, and metabolic signaling pathways. These systems work together to maintain constant communication between the gut and brain, allowing the body to respond to changing conditions, regulate mood and behavior, and maintain overall physical and mental health.
How does your gut microbiome affect your mood?
So, we’ve learned that the brain and gut are in a continuous state of communication, but how does the gut microbiome affect how you feel?
Remember the trillions of microorganisms living inside your digestive tract? They’re not just involved in digestion, they’re actively participating in the biochemical signaling that connects your gut to the brain via the gut-brain axis.
The microbiota interact closely with the ENS located inside your gut lining, maintaining continuous communication that affects both your physical and emotional well-being. This three-way relationship is referred to as the ‘microbiota-gut-brain axis’.
Below are some ways that your gut microbiome can influence your mood:
Producing neurotransmitters
Neurotransmitters are the chemical messengers that regulate thoughts, emotions, and behavior. The gut microbiome not only responds to these neurotransmitters but also produces them, including:
- Serotonin: Serotonin is crucial for mood regulation, and about 95% of the body’s serotonin is produced in the gut with the help of gut microbes
- Dopamine: Dopamine is associated with motivation and reward
- GABA: GABA is a calming neurotransmitter that helps reduce anxiety
- Norepinephrine: Norepinephrine is involved in attention and stress responses.
Gut microbes also help process tryptophan, which is an amino acid needed for serotonin production. Variations in gut bacteria populations can influence how much tryptophan your body has available, which ultimately affects serotonin levels and mood.
Keep Reading: What to Do When Antidepressants Don’t Work for You (and Why)
Regulating hormones
The gut microbiome also affects the secretion of important hormones by gut cells, including:
- Leptin and ghrelin, which regulate hunger and satiety
- Insulin, which impacts metabolism and energy use.
These hormones regulate eating behavior, but they’re also linked to learning, memory, and emotional regulation. The brain also sends hormonal signals back to the but, creating a dynamic feedback loop that can change depending on your mental and physical health.
Postbiotics and brain health
Postbiotics are bioactive compounds produced by gut microbes, and they also play an important role in brain health. Microbial activity in the gut creates a range of postbiotics, including:
- Amino acids: Building blocks of neurotransmitters
- Glucose: Fuel for the brain’s energy metabolism
- Short-chain fatty acids (SCFAs): Important for brain development.
These serve as nutrients for the brain and are transported from the gut via the bloodstream. SCFAs, in particular, help strengthen the blood-brain barrier and regulate immune responses in the brain. They’ve been shown to reduce neuroinflammation, which is one of the factors linked to depression and cognitive decline.
Immune system and inflammation
The gut microbiome also plays an important role in regulating the body’s immune system. It helps maintain the integrity of two important barriers:
- The intestinal mucosal barrier, which protects the gut lining
- The blood-brain barrier, which protects the brain.
When a person’s gut health is compromised, say due to stress, infection, poor diet, or dysbiosis, these barriers can weaken. This leads to more inflammation and alters communication along the gut-brain axis. Chronic inflammation is increasingly shown to be linked to mental health disorders such as anxiety and depression, and even neurodegenerative diseases like Alzheimer’s and Parkinson’s.
How to improve your gut microbiome for mental health
Now that we’ve seen the incredible role of gut microbiota on our brain function and health, let’s look at what we can do to keep it healthy. Below are some ways to support mental health by improving your gut microbiome:
Eat a diverse range of plant-based foods
A healthy gut microbiome loves variety. Studies show that people who eat a wide range of plant-based foods, like vegetables, fruits, legumes, beans, and whole grains, have greater microbial diversity, which is in turn associated with improved health outcomes.
These plant foods are rich in prebiotics (e.g dietary fiber and complex carbohydrates), which are used as fuel by ‘beneficial’ gut bacteria that support the body’s brain function and mood regulation.
Focus on fiber
Soluble fiber can be found in foods like asparagus, garlic, onions, oats, and beans, and it plays an important role in feeding gut bacteria and producing beneficial SCFAs. In one randomized controlled trial, it was found that a high-prebiotic diet improved mood, stress, anxiety, and sleep in individuals with moderate psychological distress. In fact, consuming foods high in fiber was found to be more beneficial than taking probiotic supplements.
Include fermented foods
Fermented foods are rich in probiotics, which are live bacteria that can replenish and support the gut microbiome. Some examples of fermented foods include:
- Plain yoghurt with live and active cultures
- Kimchi
- Sauerkraut
- Kombucha
- Tempeh
- Kefir
- Miso
- Sourdough bread.
It’s always better to choose unsweetened, minimally processed fermented foods where possible.
Keep Reading: How Successful is TMS Therapy?
Eat foods high in polyphenols and antioxidants
Polyphenols are naturally occurring compounds that promote the growth of beneficial bacteria and help reduce inflammation. Some foods rich in polyphenols include:
- Dark chocolate and cocoa
- Green or black tea
- Coffee (in moderation)
- Blueberries, blackberries, and strawberries
- Grapes, cherries, and apples
- Nuts and seeds (e.g. walnuts, flaxseeds, almonds)
- Vegetables like broccoli, carrots, and asparagus
- Herbs and spices like cinnamon, cloves, rosemary, and thyme.
Minimize highly processed foods
Diets that are heavy in processed and ultra-processed foods, like sugary snacks, fast food, instant noodles, and soda, can disrupt your gut microbiome, cause inflammation, and negatively affect your mood.
Try to limit your intake of processed foods and focus on real, whole ingredients to create an environment where beneficial microbes can flourish.
How to nurture your brain for better gut health
Your gut microbiome plays an important role in mental health, but don’t forget – the relationship is bidirectional! This means that your brain can also influence the composition and function of your gut microbes.
Decades of research have shown that stress has a negative impact on the gut microbiome. Stress can affect the microbiota both directly, by altering gut microbial populations, and indirectly, by changing the gut environment itself. Because the CNS and ENS are so closely linked, activating one system often triggers a response in the other.
Excessive or chronic stress can:
- Disrupt the movement of contents in the gut, reducing the delivery of nutrients needed for microbial growth
- Impair the secretion of protective mucus in the gut lining, which can weaken the intestinal mucosal barrier
- Decrease microbial diversity and lead to an imbalance in gut bacteria populations.
So, what can you do? Two options are:
- Cognitive-Behavioral Therapy (CBT): In one study involving individuals with irritable bowel syndrome (IBS), it was found that those who completed CBT experienced changes in brain activity as well as shifts in the relative abundance of certain gut microbes. It’s believed that CBT helped introduce flexible thinking patterns and reduce stress, which in turn nurtured gut health.
- Mindfulness and meditation: Another study looked at individuals who practiced long-term, regular meditation and found distinct differences in their gut microbiota compared to non-meditators. These findings suggest that mindfulness-based practices could potentially create a more diverse and resilient gut environment.
Professional help is here when you need it
Balancing your gut microbiome can go a long way in improving mood, but it’s no substitute for professional help. If you or someone you know is experiencing depression, anxiety, or another mental health disorder, our compassionate team at BestMind Behavioral Health is here to help.
Contact us today to book a consultation or discuss your options.
