A reader asked me to talk about “the link between the gut biome and mental health/brain function.” Since this is such a key component of my work, I was surprised I had only touched on it along the way and never dug in! Well, Greg, here you go! Thanks for the question! In Wellness, Mary Virginia In functional medicine and nutrition, we take a systems approach to get to the root causes of disease and dysfunction. One of the biggest contributors to all kinds of illness is an unhealthy digestive tract and microbiome (you’ll remember I talked about this here). It’s every bit the same for mental and brain health. Bring this into your own personal life. How is your mood when you have heartburn, indigestion, diarrhea, or constipation? What happens to your energy? Your sleep? Do you find you’re grumpier? More anxious? Do you battle brain fog or forgetfulness? What happens to your ability to focus or process information? I’ll walk you through the connection between inflammation, the gut microbiome, the gut’s nervous system, and brain and mental health. The upshot is that digestive health, mood, and brain health are inextricably intertwined. Immune System About 70% of our immune system can be found lining the walls of our gut. Healthy gut wall barriers and the immune system work to protect us from most of what travels through (viruses, bacteria, random junk, and other pathogens) that could make us sick. A healthy digestive tract maintains a strict gatekeeping process that serves to allow only safe and useful things, like nutrients, inside the body. This is important as the digestive tracts itself starts and ends with access points outside of the body (i.e. the mouth and anus respectively). We’re Looking at You, Inflammation Inflammation is the first step taken by the immune system. The five characteristics are: redness, swelling, heat, and loss of function. Swelling is the part that makes space between cells so that the metaphorical EMT’s can get through. These are chemicals that battle infection and repair damage. The cells of our digestive tract are only one layer deep. They are tightly bound together to keep stuff that’s inside the tube from slipping between them into the bloodstream. They are also covered with a thick protective layer of mucus to keep the cells from being damaged. A poorly maintained digestive tract begins to break down. Cells become fragile. The mucosal layer starts to become thin. So the immune system ramps up inflammation to treat the damage. When that happens, the cells are no longer tightly bound. You may have heard this called “leaky gut.” Molecules that should stay in the digestive tract slip between the cells into the bloodstream. The immune system throughout the body identifies these as invaders, and creates more inflammation. Note also that chronic stress undermines digestion and triggers inflammation. Poor digestion alone creates a continual stress response in the body, which is its own merry-go-round with gut health, mood, and brain health. I wrote about the role of stress resilience and mood here. Blood Brain Barrier Leaky gut also risks a leaky blood brain barrier (BBB), which is the brain’s protective layer. It’s different from the digestive tract, but serves a similar protective purpose and is also only one cell deep. “Invading” molecules travel in the bloodstream from the gut to the BBB, which triggers an immune reaction and a leaky BBB. This allows the cascade of inflammation to reach the brain. Many psychiatric disorders are associated with inflammation in the brain. For example, depression has long been associated with it. An inflamed gut and a compromised microbiome are also contributors to blood sugar dysregulation. Persistent blood sugar dysregulation is a primary foundation of diabetes, heart disease, vascular dementia, and Alzheimer’s disease. It all starts in the gut. An important answer to preventing inflammation in the gut is assuring a healthy gut microbiome. You’ll learn all about that in a bit. But first, let me tie in the nervous systems. Two Brains, One Integrated Response You know about the Central Nervous System (CNS), which consists of the brain and spinal cord. Perhaps you also are aware that the digestive tract has its own nervous system, called the Enteric Nervous System (ENS). It can also be found embedded in the walls along the entire digestive tract. The CNS and the ENS are connected to each other through the vagus nerve (the vagus nerve is so cool! You can read about it here), and that is a primary way that the gut communicates to the brain. What very few people know is that the ENS (gut) almost completely mirrors the CNS (brain) with the neurotransmitters (electrical messengers) it produces. Familiar neurotransmitters are the mood related chemicals called serotonin and dopamine. Low levels of these are associated with depression, agitation, irritation/anger, lack of motivation, sleep disruptions, issues with focus and attention, and more. Here’s the kicker: the ENS produces about 90% of the body’s entire pool of serotonin and an only slightly lower percentage of dopamine, as well as other lesser known, but important, mood chemicals. That is, it’s your gut that’s keeping your mood steady. Here’s another astonishing example: Parkinson’s disease starts in the gut. It begins with a protein that gets folded wrong in the ENS. Here’s the really wild part: each misfolded protein teaches the next proteins like it to fold the wrong way. The misfolded proteins travel up the vagus nerve into the part of the brain that controls motion, retraining every next protein in the chain reaction to fold and act differently. This is the trigger for Parkinson’s disease. Beneficial Bugs We all agree that we want to encourage a balanced mood and maintain brain health by reducing inflammation and bolstering neurotransmitter production. I see nodding heads in my audience. Luckily, there’s a single strategy that addresses all of this, and it’s all wrapped up in the gut microbiome. Our five pound collection of bacteria and other microbes in our gut microbiome really do a lot for us when we tend to it. People compare it to a garden, and it’s really true. We want to crowd out and “weed” the microbes that are only in it for themselves (selfish beasties) and nourish those that maintain their healthy living space by supporting the health of their human host. Certain types of bacteria are well known for their role in partnering with the immune system and healing the cells, the tight junctions between them, and rebuilding the protective mucosal layer. And what these thrive on is fiber from our food. Well nourished “good” bacteria proliferate (like tribbles. Star Trek fans?), and they produce a critical nutrient for the cells called short chain fatty acids (SCFA). So imagine. Now you have healthy, robust, tightly bound cells in the digestive tract walls. The mucosal layer is constantly maintained (the old, worn out mucus is literally eaten by some bacteria while other bacteria encourage the production of fresh new mucus. It sounds gross, but we really want this). Out of this blossoms a reduction in inflammation in the digestive tract, which leads to less inflammation in the body overall, and the blood brain barrier and brain reap the benefit. Fun Fact: All of this makes a difference to allergy sufferers, too. When you think about it, allergies are just another form of inflammation caused by something the body considers to be an invader. But Wait, There’s More! Short chain fatty acids also transport through the cells to the enteric nervous system, which is the source of those beautiful mood supportive neurotransmitters. The presence of SCFA’s triggers the release of serotonin and dopamine. These actually travel up the vagus nerve, attaching to serotonin and dopamine receptors across the body before reaching the brain (it’s actually a chain reaction of neurotransmitter production, not just some from the gut). Good mood is a full body experience. You know a quick way to deliver short chain fatty acids to the gut? A piece of buttered whole grain toast! Butter contains the SCFA called butyrate. The carbs in the bread give energy to the cells (also a mood booster), and the fiber in the whole grains feed those lovely SCFA-producing bacteria. An Apple a Day… Prebiotic fibers like inulin & pectin are amazing fiber food for beneficial bacteria. When you learned as a child that an apple a day keeps the doctor away, it’s because apples contain pectin (well, and a bunch of vitamins). When we chew the apple thoroughly (or cook it), pectin is released. It lands in the colon and is consumed by the good bacteria of the microbiome. Pectin is found in most fruits and vegetables. Among fruit, apples, peaches, oranges, grapefruits, apricots, lemons, and tomatoes contain the highest concentration. Rich vegetable sources are carrots and potatoes. The best legume source is peas. Inulin is also easy to find. It’s rich in asparagus, bananas, garlic and onions. Other sources include burdock, chicory (used in salads), dandelion root, Jerusalem artichokes, and leeks. The upshot is that fiber and probiotic foods are the darlings of gut health (again, read more here). Variety in food choice leads to better health from every angle, and that includes fiber sources. Choose from a wide range of whole, colorful vegetables, whole grains, whole fruits, legumes, beans, nuts, and seeds. Also look to probiotic-rich food sources, like yogurt, sauerkraut, kimchi, kombucha, and real pickles (not the kind made with vinegar). Anti-Inflammatory and High Fiber All the Way! I have already written about a food plan/guide that supports a healthy overall immune response and digestion, so I will refer you to this article so you can read all about it! And check out the antioxidant and anti-inflammatory roles of phytonutrients in colorful vegetables and fruit in this article.
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AuthorI am Mary Virginia Coffman (I go by “Mary Virginia”), a clinical nutritionist who focuses on mental health, digestive health, metabolic health, and nervous system regulation. My unique combination of clinical interventions, education, and coaching will help you feel well in body, mind, and spirit. Categories |