If you know anything about gut health, it’s probably the importance of the live bacteria that line your digestive tract. But you probably don’t know about the intricate relationship your gut has in communicating with your brain and impacting every physiological action in your body from immunity to metabolism.
This article will explain the three pathways that connect the gut with your brain to regulate all aspects of human function and highlight the impact on immunity.
The live bacteria in your gut are known as your microbiome. There are literally billions of bacteria that impact cells, genes, and DNA, affecting all systems in the body. The microbiome communicates with the brain to influence physiology through three pathways:
1. Endocrine hormone release
2. Nerve transmission
3. Immune activation
Endocrine cells of the gut release neurotransmitters and hormones such as cortisol, tryptophan, and serotonin, which communicate directly with the brain. These compounds impact mood, ability to handle stress, sleep and wakefulness, hunger and food cravings, pain tolerance, and physical performance. Studies show that when you are under stress and have higher levels of the stress hormone cortisol circulating, your immune system is not as robust and you are more likely to get sick.
The intestinal nervous system forms synaptic connections with the vagus nerve, directly connecting the gut with the brain and regulating your ability to rest and recover from both physical and mental stress. The vagus nerve governs the parasympathetic nervous system (versus the sympathetic nervous system) and studies show that stimulating it can lead to lower levels of inflammatory markers that can impede your body’s ability to fight off an illness. Scientists are currently exploring the use of electrical pulses to stimulate the vagus nerve to treat autoimmune diseases.
The microbiome also interact with immune cells, of which over 70 percent reside in the gut. These immune cells regulate your body’s response to illness and injury. Immune cells also play a role in prevention of chronic diseases, like cancer, heart disease, and diabetes because of how they alter levels of inflammatory molecules known as cytokines. Additionally, the gut is the site of much of your lymphatic system, which plays a central role in defending your body against viruses, bacteria, and foreign pathogens. When the lymphatic system is compromised, you are more likely to get acute illnesses and will have a harder time recovering.
In practical terms, this trifecta of pathways means that the gut has its own ability to impact functions we usually attribute to the brain. In fact, the gut works independently from your rational brain, regulating immunity, coordinating our stress response, influencing our emotions, and dictating our decision making.
How Can You Improve The Health & Function of Your Gut Brain Axis?
The key to improving gut health is with a robust and favorable composition of gut bacteria. This can be accomplished with the following actions:
Eat Plenty of Plant Foods: There’s no need to shun meat and dairy or go vegetarian, but including vegetables, nuts, fruits, beans, and grains in your diet will provide the phytonutrients your body needs to counter inflammation and fight off disease.
Include Prebiotic Fibers In Your Diet: Prebiotics are a type of fiber that feed the healthy bacteria in the GI tract. They are found in foods like bananas, onions, garlic, the skin of apples, oats, beans, and many other plant-based foods.
Include Probiotic Foods In Your Diet: Probiotics are the beneficial bacteria that make up your microbiome and communicate with your brain. They are found in fermented foods, including dairy, sauerkraut and other fermented vegetables, and kombucha tea. A probiotic supplement is also an option because this is a good way to dose your body with a high concentration of healthy bacteria that are shown in research studies to improve immunity and counter stress.
Moderate Caffeine: Caffeine can be a great tool for boosting physical performance and coffee consumption is associated with a healthier microbiome, but it also raises cortisol and can be more trouble than it’s worth If you find yourself using it as a crutch throughout the day.
Avoid Toxins: Although the GI tract has a robust system for eliminating toxins, it can get overloaded if you aren’t careful. Your liver and gut deal with excess hormones, metabolic waste, pharmaceuticals, chemical compounds, and pesticides, which can harm the gut bacteria and negatively impact immunity if you aren’t careful.
Incorporate Fasting: There’s no need to go crazy with long duration fasts, but spacing out your meals by at least four hours and using time-restricted feeding so that you eat over an 8- to 12-hour period during daylight will improve the microbiome and give your gut a chance to rest and recover. The chronic eating and snacking that typifies many modern lifestyles is associated with increased inflammation, obesity, and a poorer immune response.
Carabotti, M., et al. The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Annals of Gastroenterology. 2015. 28(2), 203-209.
Fung, T. The microbiota-immune axis as a central mediator of gut-brain communication. Neurobiological Diseases. 2020. 136, 104714.
Mayer, E., et al. Gut/brain axis and the microbiota. Journal of Clinical Investigation. 2015. 125(3), 926-938.