Your gut and brain are constantly conversing. It’s like a silent Morse code clicking away throughout the day. You may not hear it, but you’re steering the discussion.
This two-way communication system is called the gut–brain axis. It’s a crucial part of the GI microbiome, a complex ecosystem of bacteria, viruses, fungi, and other microorganisms that plays a significant role in overall health.
How the brain and gut communicate
The vagus nerve is an essential link between the brain and gut, but other systems, including the immune, nervous, neuroendocrine, and circulatory systems, also act as communication pathways. This interconnectedness influences health in numerous ways.
“The gut is often referred to as a second brain [because of] its profound influence on various organs throughout the body, including the brain,” says Arpana Church, PhD, neuroscientist, associate professor at the UCLA David Geffen School of Medicine, and co-director of the UCLA Goodman–Luskin Microbiome Center. “Traditionally, when we think about medicine, it’s very siloed. If we have a problem with the heart, we see a cardiologist. If there’s cancer, we see an oncologist. But when we talk about the gut microbiome and the gut–brain axis, we are really looking at medicine and the body as a system, which is more realistic because everything is connected.”
Inside the gut, beneficial bacteria line the intestinal walls, acting as a defense against harmful invaders like viruses. But when harmful microorganisms take over, they can damage the intestinal lining, triggering inflammation and allowing toxins to leak into the bloodstream, including the brain. This imbalance, called dysbiosis, has been linked to central nervous system disorders, cognitive decline, and depression.1Peterson C, Round JL. Defining dysbiosis and its influence on host immunity and disease. Cell Microbiol. 2014;16(7):1024-1033. https://doi.org/10.1111/cmi.12308,2Almeida C, Oliveira R, Soares R, Barata P. Influence of gut microbiota dysbiosis on brain function: a systematic review. Porto Biomedical Journal. 2020;5(2):1-8. https://doi.org/10.1097/j.pbj.0000000000000059
Gut health, mood, and memory
The gut–brain axis influences mood and mental well-being by regulating key neurotransmitters like dopamine, serotonin, and melatonin.3Toader C, Dobrin N, Costea D, et al. Mind, mood and microbiota—gut-brain axis in psychiatric disorders. Int J Mol Sci. 2024;25(6). https://doi.org/10.3390/ijms25063340
Multiple studies confirm the role of the gut–brain connection in mental health. As research evolves, experts are increasingly recommending that clinicians assess gut function as part of treatment for conditions like anxiety and depression.4Faraj J, Takanti V, Tavakoli HR. The gut-brain axis: literature overview and psychiatric applications. Federal Practitioner. 2021;38(8):356-362. https://doi.org/10.12788/fp.0159
A balanced gut microbiome can also help manage stress. It regulates the body’s circadian system, which controls the sleep–wake cycle. Gut bacteria influence how we respond to stress, and this effect changes depending on the time of day. Sleep quality affects mood, brain function, and overall health.5An E, Delgadillo DR, Yang J, et al. Stress-resilience impacts psychological wellbeing as evidenced by brain-gut microbiome interactions. Nat Mental Health. 2024;2. https://www.nature.com/articles/s44220-024-00266-6,6Tofani G, Leigh S, Gheorghe CE, et al. Gut microbiota regulates stress responsivity via the circadian system. Cell Metab. 2024;37:1-16. https://doi.org/10.1016/j.cmet.2024.10.003
Beyond mood, the gut–brain axis also contributes to cognitive function and the risk of neurodegenerative diseases. A healthy microbiome supports memory, learning, and attention.7Tooley KL. Effects of the human gut microbiota on cognitive performance, brain structure and function: a narrative review. Nutrients. 2020;12(10). https://doi.org/10.3390/nu12103009 On the other hand, poor gut health has been linked to Alzheimer’s disease, Parkinson’s disease, and other neurological disorders.2Almeida C, Oliveira R, Soares R, Barata P. Influence of gut microbiota dysbiosis on brain function: a systematic review. Porto Biomedical Journal. 2020;5(2):1-8. https://doi.org/10.1097/j.pbj.0000000000000059
A 2023 study found that gut–brain disorders are “highly prevalent” and significantly influence quality of life across physical, mental, and social domains.8Knowles SR, Skvarc D, Ford AC, et al. Negative impact of disorders of gut-brain interaction on health-related quality of life: results from the Rome Foundation Global Epidemiology Survey. Gastroenterology. 2023;164(4):655-688. https://www.gastrojournal.org/article/S0016-5085(22)01393-2/fulltext
Foods, supplements, and good gut habits
Diet, obesity, medications, and aging all influence the gut–brain axis. However, positive lifestyle choices can improve gut health and, in turn, brain function.9Lu S, Zhao Q, Guan Y, et al. The communication mechanism of the gut-brain axis and its effect on central nervous system diseases: a systematic review. Biomed Pharmacother. 2024;178. https://doi.org/10.1016/j.biopha.2024.117207
“Influencing the gut–brain axis is easier and faster than people may think,” notes Dr. Church. “What you do today to positively enhance gut health will have profound impacts even within 24 hours.”10Alcock J, Maley CC, Aktipis CA. Is eating behavior manipulated by the gastrointestinal microbiota? Evolutionary pressures and potential mechanisms. Bioessays. 2014 Oct;36(10):940-9. https://doi.org/10.1002/bies.201400071
Reducing ultra-processed foods—soda, sweets, bacon, ham, cereals, and fast food—can help restore gut balance by reducing inflammation. These dietary improvements enhance brain function, mood, and behavior.11Song Z, Song R, Liu Y, et al. Effects of ultra-processed foods on the microbiota-gut-brain axis: the bread-and-butter issue. Food Res Int. 2023;167. https://doi.org/10.1016/j.foodres.2023.112730
Focusing on plant-based foods further supports the gut microbiome.12Shi R, Huang C, Gao Y, et al. Gut microbiota axis: potential target of phytochemicals from plant-based foods. Food Sci Hum Well. 2023;12(5):1409-1426. https://doi.org/10.1016/j.fshw.2023.02.001 The Mediterranean diet, rich in polyphenols, polysaccharides, healthy fats, and fiber, is one effective approach.13Merra G, Noce A, Marrone G, et al. Influence of Mediterranean diet on human gut microbiota. Nutrients. 2020 Dec 22;13(1):7. https://doi.org/10.3390/nu13010007
Dietary supplements can also support gut and brain health. Prebiotics (which feed good bacteria) and probiotics (which introduce beneficial bacteria) have shown promise in improving gut health.14Ansari F, Neshat M, Pourjafar H, et al. The role of probiotics and prebiotics in modulating the gut-brain axis. Front in Nutr. 2023. https://doi.org/10.3389/fnut.2023.1173660 A 2024 review found that probiotics and prebiotics may help treat depression and anxiety.3Toader C, Dobrin N, Costea D, et al. Mind, mood and microbiota—gut-brain axis in psychiatric disorders. Int J Mol Sci. 2024;25(6). https://doi.org/10.3390/ijms25063340
Omega–3 fatty acids also contribute to gut microbiome diversity and play a crucial role in brain function.15Menni C, Zierer J, Pallister T, et al. Omega-3 fatty acids correlate with gut microbiome diversity and production of N-carbamylglutamate in middle aged and elderly women. Sci Rep. 2017;7. https://doi.org/10.1038/s41598-017-10382-2
Additionally, exercise positively influences the gut–brain axis, while consistent, high-quality sleep maintains balance between the two systems.16Dalton A, Mermier C, Zuhl M. Exercise influence on the microbiome-gut-brain axis. Gut Microbes. 2019;10(5):555-568. https://doi.org/10.1080/19490976.2018.1562268,17Wang Z, Wang Z, Lu T, et al. The microbiota-gut-brain axis in sleep disorders. Sleep Med Review. 2022. https://doi.org/10.1016/j.smrv.2022.101691
Dr. Church emphasizes that the gut–brain axis is a two-way street. “If you do things to enhance brain health, it will also enhance gut health,” she said. “Being more mindful, as well as focusing on stress management, social connection, and doing things to improve our brain function will all help enhance the gut–brain axis.”
Footnotes
- 1Peterson C, Round JL. Defining dysbiosis and its influence on host immunity and disease. Cell Microbiol. 2014;16(7):1024-1033. https://doi.org/10.1111/cmi.12308
- 2Almeida C, Oliveira R, Soares R, Barata P. Influence of gut microbiota dysbiosis on brain function: a systematic review. Porto Biomedical Journal. 2020;5(2):1-8. https://doi.org/10.1097/j.pbj.0000000000000059
- 3Toader C, Dobrin N, Costea D, et al. Mind, mood and microbiota—gut-brain axis in psychiatric disorders. Int J Mol Sci. 2024;25(6). https://doi.org/10.3390/ijms25063340
- 4Faraj J, Takanti V, Tavakoli HR. The gut-brain axis: literature overview and psychiatric applications. Federal Practitioner. 2021;38(8):356-362. https://doi.org/10.12788/fp.0159
- 5An E, Delgadillo DR, Yang J, et al. Stress-resilience impacts psychological wellbeing as evidenced by brain-gut microbiome interactions. Nat Mental Health. 2024;2. https://www.nature.com/articles/s44220-024-00266-6
- 6Tofani G, Leigh S, Gheorghe CE, et al. Gut microbiota regulates stress responsivity via the circadian system. Cell Metab. 2024;37:1-16. https://doi.org/10.1016/j.cmet.2024.10.003
- 7Tooley KL. Effects of the human gut microbiota on cognitive performance, brain structure and function: a narrative review. Nutrients. 2020;12(10). https://doi.org/10.3390/nu12103009
- 8Knowles SR, Skvarc D, Ford AC, et al. Negative impact of disorders of gut-brain interaction on health-related quality of life: results from the Rome Foundation Global Epidemiology Survey. Gastroenterology. 2023;164(4):655-688. https://www.gastrojournal.org/article/S0016-5085(22)01393-2/fulltext
- 9Lu S, Zhao Q, Guan Y, et al. The communication mechanism of the gut-brain axis and its effect on central nervous system diseases: a systematic review. Biomed Pharmacother. 2024;178. https://doi.org/10.1016/j.biopha.2024.117207
- 10Alcock J, Maley CC, Aktipis CA. Is eating behavior manipulated by the gastrointestinal microbiota? Evolutionary pressures and potential mechanisms. Bioessays. 2014 Oct;36(10):940-9. https://doi.org/10.1002/bies.201400071
- 11Song Z, Song R, Liu Y, et al. Effects of ultra-processed foods on the microbiota-gut-brain axis: the bread-and-butter issue. Food Res Int. 2023;167. https://doi.org/10.1016/j.foodres.2023.112730
- 12Shi R, Huang C, Gao Y, et al. Gut microbiota axis: potential target of phytochemicals from plant-based foods. Food Sci Hum Well. 2023;12(5):1409-1426. https://doi.org/10.1016/j.fshw.2023.02.001
- 13Merra G, Noce A, Marrone G, et al. Influence of Mediterranean diet on human gut microbiota. Nutrients. 2020 Dec 22;13(1):7. https://doi.org/10.3390/nu13010007
- 14Ansari F, Neshat M, Pourjafar H, et al. The role of probiotics and prebiotics in modulating the gut-brain axis. Front in Nutr. 2023. https://doi.org/10.3389/fnut.2023.1173660
- 15Menni C, Zierer J, Pallister T, et al. Omega-3 fatty acids correlate with gut microbiome diversity and production of N-carbamylglutamate in middle aged and elderly women. Sci Rep. 2017;7. https://doi.org/10.1038/s41598-017-10382-2
- 16Dalton A, Mermier C, Zuhl M. Exercise influence on the microbiome-gut-brain axis. Gut Microbes. 2019;10(5):555-568. https://doi.org/10.1080/19490976.2018.1562268
- 17Wang Z, Wang Z, Lu T, et al. The microbiota-gut-brain axis in sleep disorders. Sleep Med Review. 2022. https://doi.org/10.1016/j.smrv.2022.101691
