What is the Gut Brain Axis?

What is the Gut Brain Axis?

  • Gut Health

  • By Jef L’Ecuyer, Registered Dietitian

    Have you ever felt “butterflies” before going on a first date or a knot in the pit of your stomach in anticipation of speaking in public? 

    This sensation indicates more than excitement about a budding romance or nervousness about a public speaking blunder. It’s not “all in your head,” as some people might tell you. It’s actually in your body, too, and points to a significant connection between the brain and the gut, known as the gut-brain axis. 

    In this article, we’ll explain how the gut-brain axis works and how it relates to your mood, emotions, and stress response. We’ll also offer some tips on how to improve your diet to optimize your gut health. 

    The Gut-Brain Axis—Explained 

    The gut brain axis is a two-way communication system between the gastrointestinal tract (your gut) and the central nervous system (for all intents and purposes, your brain). Each of these key components is already complex in its own right:

    • The central nervous system – The central nervous system (CNS) encompasses the brain and the spinal cord. It plays many roles within the body, controlling both physical and behavioral elements, including voluntary movements, perception, sensation and language.⁴

    The CNS contains around 86 billion neurons. These neurons can transmit and receive information from each other. In turn, they enable us to sense the world around us, feel our emotions, make decisions, and take action.

    • The gut (the “second brain”) – The gut is often referred to as the “second brain” since it also features a powerful nervous system, known as the enteric nervous system (ENS). The ENS has many important digestive functions, the main ones being controlling the movement in the gastrointestinal tract and regulating the secretion of digestive enzyme. 

    The ENS contains a network of 200-600 million neurons, which surround  the gastrointestinal tract. Even if the ENS is thought of as an independent system from the CNS, they are closely connected. 

    While these two systems work independently of one another, they communicate in fascinating ways. There is still a lot of research to be done, but it appears that they communicate primarily through the vagus nerve, the main nerve in your body that connects everything from your lungs to your heart to your digestive system. 

    What is the Microbiota-Gut-Brain Axis?

    The gut is home to a thriving ecosystem of bacteria, called gut flora. Most people have around 150 distinct species of bacteria in their gut! The bacteria found in a healthy gut microbiota  outnumber the number of human cells in your body by about 40%. 

    Healthy gut bacteria play a large role in the gut brain axis. As time goes on, researchers continue to discover more ways that the gut microbiota can influence many brain-related functions, including:

    • Pain perception
    • Ability to learn new things
    • Stress response
    • Depression
    • Memory

    The two-way communication between the gut microbiota and the central nervous system is known as the microbiota gut brain connection or axis.

    How Does the Microbiota Gut-Brain Axis Work?

    Your gut’s microbiota and your brain communicate using a variety of mechanisms, including the vagus nerve, the immune system, and the ENS.

    Due to their two-way communication, research shows a notable crossover between gut dysbiosis (change in good bacteria to bad bacteria ratio)and cognitive disorders. 

    There are statistically significant connections between people with gastrointestinal problems and certain mental disorders.

    Serotonin and the Gut

    Serotonin is an important neurotransmitter that plays many different roles. They range from regulating GI movements in the ENS to stabilizing mood and modulating anxiety and sleep in the CNS.¹³ Decreased serotonin production can even lead to depression. 

    While depression is often thought of as an imbalance of neurotransmitters in the brain, its root may come from the gut. That’s because your gut produces 95% of your body’s serotonin. Gut bacteria use tryptophan from your diet to create this vital neurotransmitter, which then becomes available to your brain. Some studies show that probiotics can increase your gut’s production of tryptophan, which then allows you to produce more serotonin. 

    And who couldn’t benefit from a little more of the “happiness gut hormone”?

    The Brain Impacts the Gut, Too

    In stressful situations, a “fight or flight” response is initiated. In that case, the brain is the one influencing the gut, not the other way around. In fact, when facing a stressful situation, the hypothalamus (a region of the brain) stimulates the release of cortisol by the adrenal glands. Cortisol is a steroid hormone more commonly known as the “stress hormone”.¹⁴ 

    Once released into circulation, cortisol plays many roles, including influencing the gut and microbiota. In stressful situations, cortisol redirects blood flow from the gut to the brain. This ensures you can think clearly, but it also stops digestion.¹⁵ 

    Chronic stress and cortisol production can also cause a “leaky gut”. Bacteria can then enter the bloodstream, causing an inflammatory response. Chronic stress also affects the gut microbiota, causing an increase in pro-inflammatory bacteria (bad bacteria).¹⁶ 

    Stress can have harmful effects on the gut and microbiota. This can lead to increased inflammation in the CNS and cognitive impairments down the line.¹⁷ This vicious circle in the stress response illustrates clearly the two-way communication inside the microbiota-gut-brain axis. 

    The Gut Brain Axis Diet

    Everything we eat impacts our health, whether it’s physically, mentally, or both. Our gut microbiota ‘eat’ the same things we do, so our diet influences our gut microbiota composition. If you want to enjoy the best possible health outcomes, it’s important to eat a diet that supports your gut health. 

    You may be able to optimize the composition of your gut microbiota by consuming more foods that contain or promote “good” bacteria and limiting foods that feed the “bad” bacteria. This will facilitate a healthy communication through the microbiota-gut-brain axis. 

    How can you make good choices that will help your whole body? We’ve got you covered.

    #1 Add Probiotics to Your Diet

    Probiotics are like the superheroes of gut health. They are good bacteria or yeasts that positively impact your overall digestion. Fermented foods are known to naturally contain some good-for-your-gut bacteria. It’s important to note that not all fermented foods contain probiotics. Here’s a list of fermented foods you can add to your diet to promote digestive health:¹⁸

    • Yogurt
    • Tempeh
    • Kombucha
    • Kefir
    • Kimchi
    • Miso

    If you want to guarantee a daily probiotic intake, you can choose a daily probiotic supplement of either Bio-K+ drinkables or convenient capsules to support gut health.

    Due to the far-reaching impacts of the gut brain axis, consuming probiotic supplements has been linked to:⁶

    • Reduced anxiety and depression
    • Improved brain function
    • Improved memory and learning abilities

    When selecting a probiotic supplement, it’s important to remember that not all probiotics are equal and have the same beneficial effects. By selecting Bio-K+, you choose a unique probiotic formula supported by several years of clinical research.

    #2 Include More Prebiotic Fibers in Your Diet

    When taking probiotics, you give good bacteria to your gut. Another way to support a healthy microbiota is by giving food to the good bacteria already in your gut. You can do so by eating foods that contain prebiotics.  

    Prebiotics are non-digestible fibers that feed the good bacteria in your gut. You can find this type of fiber in a variety of foods, including:

    • Vegetables, such as garlic, onions, leeks, asparagus, and Jerusalem artichoke
    • Fruits, including apples and bananas
    • Oats, wheat bran, and flaxseed
    • Chicory, burdock, yacon, and jicama root
    • Seaweed

    Fortunately, many of these prebiotic foods are easy to integrate into your daily diet.

    #3 Eat More Foods with Tryptophan

    As we mentioned earlier, tryptophan is a significant building block in serotonin. There are studies that suggest that low tryptophan can have negative effects on cognition. Even though the direct link between dietary tryptophan and improved cognition¹⁹ has not been made yet, you can stack the odds in your favor by adding the following foods to your diet: 

    • Meats, including lean chicken and turkey, beef, and salmon
    • Dairy products, such as eggs, milk, and cheese
    • Firm tofu and soybeans
    • Pumpkin seeds
    • Peanuts
    • Dark chocolate
    • Oats

    By adding these already-healthy staples to your diet, you can make sure that your gut has an adequate supply of tryptophan, allowing it to produce enough serotonin to keep your mood, sleep, and appetite in tip-top shape. 

    #4 Limit Foods That Harm Gut Health

    While many foods can support your digestive health, there are also some foods you should limit. Reducing your intake of the following foods will not only help your microbiota, but your general health as well::

    • Highly processed foods
    • Artificial sweeteners
    • Refined sugar
    • Fried foods

    These foods often enable “bad” bacteria to grow in your gut, which can result in a microbiota imbalance, or dysbiosis. If this list encompasses many of your favorite indulgent foods, try to eat them in moderation. Your gut will thank you.

    Support Your Gut Health with Bio-K+ Probiotics

    As you can see, the gut’s intestinal microbiota and the brain are intertwined in surprising ways. By understanding their relationship, you can make better diet decisions and set yourself up with a happy, healthy gut—and therefore, a happy, healthy life. 

    If you’re interested in adding a high-quality probiotic into your diet, look no further than Bio-K+. Our probiotic capsules and tasty drinkables feature unique probiotics that have proven effective in clinical trials. Our delicious probiotic drinks come in a wide range of flavors, including vanilla, strawberry, raspberry, and mango. Some of these drinkables are even vegan-friendly

    The Bio-K+ plus blog also answers questions to other common questions like, “what is clean eating?”, “what is self care?”, and “what are the benefits of meditation?”. 

    By choosing Bio-K+, you can give your body (and your brain!) the very best. Learn more about Bio-K+ probiotics today.


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    Jef L’Ecuyer Registered Dietitian
    About the author
    After her nutrition training at McGill University, Jef specialized in gastrointestinal health with a special interest in the microbiota and Irritable Bowel Syndrome. With Bio-K+, she continues on this path by making the world of probiotics more accessible to all.
    View all articles by Jef L’Ecuyer
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