The Connection Between Gut Health and Brain Function

Research into the relationship between gut health and its effects on brain function has grown significantly in recent years. Scientists are now aware that the “gut-brain axis” (GBA) has an important impact on wellbeing. The gut-brain axis is a link between the brain and the gastrointestinal (GI) system, which includes the enteric nervous system and the diverse microbiome.

This article will discuss the gut-brain axis and its role in parts of the brain and their functions. We will also explain how improving gut health may have a role in the treatment and prevention of mental health disorders.

The gut-brain axis is the two-way communication path between the gut and the brain.¹ This communication pathway occurs via the vagus nerve, the largest nerve in the body. By communicating this way, the gut can directly influence our brain function and behavior, and vice versa. This is because the gut-brain network includes the central nervous system, the autonomic nervous system (ANS), the enteric nervous system (ENS), the hypothalamic pituitary adrenal (HPA) axis, and brain and spinal cord.²

While essential for normal gut function, this intricate communication system has many effects on behavior, including mood, motivation, and other cognitive functions.³ Many hormones and neurotransmitters are made in the gut, including gamma-aminobutyric acid (GABA), dopamine, serotonin, and substances produced as a result of fermentation, such as short-chain fatty acids (SCFA).⁴

Gut microbiota has a major influence on gut-brain interaction. More recent research has shown that the gut–brain axis enables gut microbiota to communicate with the brain through direct and indirect signaling pathways to influence brain physiology, function, and even behavior.⁵

Studies have linked dysbiosis and functional gastrointestinal disorders with many central nervous disorders such as autism, anxiety, and depression.⁶

The gut microbiota is a complex ecosystem comprising billions of bacteria. Gut microbiota benefits the body in a number of ways, starting with digestion. Bacteria break down complex carbohydrates and proteins from food to produce substances that are important for numerous bodily functions. Microbial communities within the gut change in composition, diversity, and activity throughout life, which also impacts behavior and cognition.⁷

Probiotics are live organisms that include bacteria and yeast and can be taken as gut health supplements. Probiotics support the health and function of the gut, which in turn can provide significant health benefits to overall wellbeing.⁸

Research suggests that probiotics can support healthy brain function and mood by enhancing the quantity and quality of gut bacteria. Several neurotransmitters including serotonin, GABA (gamma-aminobutyric acid), and glutamate are produced in the gut. In fact, around 50% of dopamine⁹ and 95% of serotonin¹⁰ is produced in the gastrointestinal tract. In addition,
the hypothalamic-pituitary-adrenal (HPA) axis is believed to be activated when gut microbiota is disrupted, leading to both inflammatory diseases and mental health disorders. There is also evidence that depression and inflammatory gut conditions occur due to poor gut health and poor diet.¹¹ A lack of mood-supporting neurotransmitters is associated with anxiety and depressive symptoms.¹²

Good sources of probiotics include fermented products such as yogurt, kefir, miso, tempeh, sauerkraut, sourdough products, kimchi, olives, and pickles.¹³

Probiotic supplements are an effective and convenient means of supporting gut microbiome. Probiotics are reported to reduce symptoms of depression as well as reducing C-reactive protein concentrations, suggesting their promising effects in treating depressive symptoms.¹⁴

Other studies have shown probiotics to have a positive effect on the gut-brain axis and mental well-being, particularly in improving mood and reducing depressive symptoms. These results demonstrate the close relationship between microbiome balance and psychological parameters, and how targeted supplementation can positively influence the gut-brain axis for improved mental wellness.

Looking for the best probiotic for gut health? Methyl-Life’s® Gut Health 4 in 1 is a full-spectrum gut health supplement to enhance microbiome health and gut barrier function. It contains prebiotics, probiotics, short-chain fatty acids, and digestive enzymes to reduce digestive inflammation and support the growth of beneficial gut bacteria. Another option - especially for those taking antibiotics - is Methyl-Life’s® RestorFlora, a spore-based probiotic that contains the beneficial yeast saccharomyces boulardii to support and regenerate gut bacteria.

Just as the brain can influence intestinal function, gut inflammation can influence mood, cognitive function, and mental health. Numerous studies have revealed a link between inflammatory bowel diseases (IBDs) and neurodegenerative diseases, particularly inflammatory bowel disease (IBD), which is closely linked to mental health disorders.¹⁵

Harmful gut bacteria can trigger an immune response, which then increases the inflammatory processes that break down the gut barrier and activate pain sensory pathways in the gut and the enteric nervous system.¹⁶

Enteric dysbiosis - an imbalance in the gut bacteria - can lead to substances from the inflamed intestines passing through the intestinal barriers into the brain. Inflammatory mediators in the gut can also cause changes in the structure and function of the central nervous system (CNS). Dysregulation of intestinal microbiota can damage the intestinal epithelial barrier leading to intestinal inflammation and sends harmful proteins from the enteric nervous system to the brain. This can not only cause further gastrointestinal dysfunction but further inflammation in the brain affecting neuroplasticity, potentially increasing the risk of diseases such as Parkinson’s.¹⁷ Studies have also highlighted the contribution of the gut microbiota to peripheral inflammation in multiple sclerosis (MS).¹⁸

The intestinal barrier requires a wide range of beneficial bacteria to maintain its strength and development. Gut bacteria provide energy in the form of short-chain fatty acids and also by releasing antimicrobial substances to inhibit pathogens.

The best gut health foods are those rich in fiber and prebiotics. A lack of fiber in the diet results in the thinning of the epithelial layer. High saturated fats and simple sugars also impair intestinal barrier integrity by reducing tight junctions and allowing the growth of harmful bacteria.

Sources of fiber include whole grains (barley, oats, brown rice, wheat), fruits, nuts, root vegetables, legumes, pulses.

The intestinal barrier requires a wide range of beneficial bacteria to maintain its strength and development. Gut bacteria provide energy in the form of short-chain fatty acids and also by releasing antimicrobial substances to inhibit pathogens.¹⁹

The best gut health foods are those rich in fiber and prebiotics. A lack of fiber in the diet results in the thinning of the epithelial layer. High saturated fats and simple sugars also impair intestinal barrier integrity by reducing tight junctions and allowing the growth of harmful bacteria.²⁰

Sources of fiber include whole grains (barley, oats, brown rice, wheat), fruits, nuts, root vegetables, legumes, pulses.²¹

Prebiotics are carbohydrates that are fermented by the gut microbiome to produce therapeutic and health-promoting compounds. These compounds can strengthen probiotic bacteria and function as a ‘fuel’.²² Good sources of prebiotics include asparagus, sugar beet, garlic, chicory, onion, yogurt, cheese, Jerusalem artichoke, green bananas, soybean, peas, beans.²³

Different gut bacteria can result in different symptoms of mood disorders. A lack of healthy gut microbiota is associated with depression, anxiety, stress, and personality changes.²⁴

Various internet sources claim that other symptoms may include difficulty sleeping, poor concentration, poor memory, and ‘brain fog’.

If you are experiencing these symptoms on a regular basis and they are affecting your daily life, it’s important to seek help from a qualified healthcare practitioner and perhaps consider a gut health test.

The gut-brain axis is a bidirectional communication system between the gut and the brain, and disruptions in the gut microbiota can significantly impact mental health and mood. However, improving the gut microbiome with a nutritious diet, prebiotics, and probiotics can reduce the inflammatory processes in the gut and brain that are linked to these mood symptoms. Check out Methyl-Life’s® comprehensive guides to improving gut health and supporting cognitive function