Gut Health and Anxiety: Understanding the Link
The gut (entire digestive system) plays a pivotal role in shaping your mental well-being and physical health, often earning it the moniker of our “second brain.” The foods we eat have an impact on the gut microbiome, which is the collective genetic material of trillions of bacteria living in our intestines, and this in turn has an impact on our mental health. Researchers have even identified specific bacteria that appear to have the greatest impact on mental health.
Anxiety, depression, and autism spectrum disorder all have well-established links to gastrointestinal dysfunction. Likewise, gastrointestinal disorders often coexist with psychological conditions.1,2
Most studies linking the gut microbiome to mental health are small, but they are impactful enough that people are experimenting with prebiotics, probiotics, and fermented drinks to improve their gut microbiome and overall health.3
Table of Contents
The Gut-Brain Axis: A Complex Communication Network
The gut-brain axis is a communication network that connects our gut and our central nervous system. This bidirectional relationship allows constant interaction and mutual influence between the gut and brain.1,4
The gut, lined with millions of nerve cells (enteric nervous system), communicates with the brain through the vagus nerve. The gut releases chemicals that influence brain functions such as pain perception, the sleep/wake cycle, feeding behavior, mood, and blood pressure regulation.1
Nerve impulses from the brain produce neurotransmitters such as serotonin and GABA in the gut. The nervous system also directly affects the gut immune system. Likewise, the gut microbiome is necessary for healthy nerve function.1
The Influence of Gut Microbiota on Mental Health
The human microbiota is the trillions of fungi, bacteria, viruses, and other microorganisms that live in your gastrointestinal system (gut). These microorganisms interact with each other and their human host as part of a microbiome.
Gut bacteria influence your metabolic rate, how you process food, gain or lose weight, your immune health, and your mood. When your gut microbiome is out of balance (dysbiosis), it can cause inflammation and disease. It may also influence your brain chemistry, which can impact your mood.1
Numerous studies have shown that the composition of our gut microbiota can influence our mood and mental state.5
Potential links between the gut microbiota and mental health include:
- Lower fecal levels of short-chain fatty acids and propionic acids produced by bacteria are more commonly found in people with depression compared to a control population.5
- Transplanting fecal material from psychologically healthy people to people with depression alleviated their depression and anxiety.5
- Lower levels of Eubacterium ventriosum have been observed in the guts of people with depression than in the control population. This suggests that these bacteria may have protective and anti-inflammatory properties.
- Certain bacteria in the gut produce short-chain fatty acids and GABA, a neurotransmitter linked to anxiety. When the gut microbiome is imbalanced, it can disrupt the production of these compounds, potentially contributing to anxiety symptoms.1
- Having generalized anxiety disorder is associated with lower fecal bacterial diversity, decreased short-chain fatty acid-producing bacteria, and changes in the proportion of gut bacteria.5
Gut microbiomes in people experiencing depression, anxiety, and bipolar disorder are more likely to have high levels of bacteria that increase inflammation and lower levels of protective bacteria.6 When the balance of gut bacteria is disrupted, it causes increased intestinal leakage. Bacterial metabolites and molecules enter the bloodstream. A leaky gut can harm the immune system and contribute to physical and mental health disorders.7
Gut Health and Anxiety: A Two-Way Street
Between 50% and 90% of people seeking treatment for functional gastrointestinal disorders have a psychiatric disorder as well. The most commonly diagnosed are anxiety and depression.8 Research suggests that anxiety is most strongly associated with nausea. It has weaker associations with heartburn, diarrhea, and constipation.9
Research demonstrating that changes in the gut microbiome can affect brain function and neurotransmitter production further supports the link between the gut and anxiety. Gut bacteria produce neurochemicals that the brain uses to regulate physiological processes, such as mood, memory, and learning.
The Role of Diet in Maintaining Gut Health
Diet is critical for maintaining a healthy gut microbiome and supporting mental well-being.
Consuming a diet rich in fiber, fruits, and vegetables provides essential nutrients that promote the growth of beneficial bacteria in the gut. These bacteria produce short-chain fatty acids that have anti-inflammatory properties and support brain health.
On the other hand, diets high in processed foods, sugar, and saturated fats can negatively impact gut health, leading to an imbalance in the gut microbiota and potential mental health implications.
Diet alterations can have a significant effect on the gut bacterial composition in as little as 24 hours. If the dietary change is temporary, the bacterial composition can be restored.7
Probiotics and their Potential Benefits for Gut Health and Anxiety
Probiotics are live microorganisms, typically yeasts and bacteria, that provide health benefits when consumed. They have gained significant attention for their potential role in supporting gut health and mental well-being. Research suggests that certain probiotics can reduce cortisol levels, reduce inflammation, and lead to a sense of well-being.7
Probiotics may restore the gut lining and reduce the leakage of inflammatory chemicals into the bloodstream. Human studies have shown that probiotics can protect the nervous system and reduce anxiety and depressive symptoms.10
It is important to acknowledge that the U.S. Food and Drug Administration does not regulate probiotics. More research is needed to better understand the potential impact of probiotics on mental health.7
Lifestyle Factors and Their Impact on Gut Health and Anxiety
In addition to diet, other lifestyle factors can impact gut health and, consequently, mental well-being. Chronic stress, lack of sleep, and sedentary behavior have been associated with changes in the gut microbiome and an increased risk of mental health disorders.11
Managing stress through relaxation techniques, engaging in regular physical activity, and prioritizing quality sleep can all contribute to a healthy gut and improved mental health.
The Importance of Individualized Care for Gut Health and Anxiety
It is important to note that the gut-brain connection is complex and varies from person to person. Diet, environmental factors, the time of year, and health status all impact it. 7 What works for one individual may not work for another, highlighting the importance of individualized care.
Healthcare providers can help individuals assess their gut health, identify any imbalances, and develop personalized strategies to improve gut health and manage anxiety. Since research on the connection between the gut microbiome and anxiety is still in its infancy and has led to inconclusive results, it is important to continue using prescribed and established treatments for depression and anxiety.12
Looking Ahead: Future Directions in Research
As our understanding of the gut-brain connection continues to evolve, future research will likely uncover more insights into the role of gut health in mental health. This includes exploring the specific mechanisms through which gut bacteria influence brain function, identifying the most beneficial bacterial strains, and developing targeted interventions to improve mental health outcomes.
For now, research supports a link between an imbalanced microbiome and anxiety. Anxiety and depression seem to be more common in people with a higher abundance of pro-inflammatory bacteria in their microbiome.2
NAD+ is a powerful antioxidant that helps neutralize cellular damage. Excess inflammation from a microbiome imbalance can stress your body’s ability to maintain healthy NAD+ levels.
- Appleton J. The Gut-Brain Axis: Influence of Microbiota on Mood and Mental Health. Integr Med (Encinitas). 2018 Aug;17(4):28-32. PMID: 31043907; PMCID: PMC6469458.
- Simpson, C. A., Mu, A., Haslam, N., Schwartz, O. S., & Simmons, J. G. (2020). Feeling down? A systematic review of the gut microbiota in anxiety/depression and irritable bowel syndrome. Journal of Affective Disorders, 266, 429–446. https://doi.org/10.1016/j.jad.2020.01.124
- Smith KS, Morris MM, Morrow CD, Novak JR, Roberts MD, Frugé AD. Associations between Changes in Fat-Free Mass, Fecal Microbe Diversity, and Mood Disturbance in Young Adults after 10-Weeks of Resistance Training. Microorganisms. 2022 Nov 26;10(12):2344. doi: 10.3390/microorganisms10122344. PMID: 36557597; PMCID: PMC9785032.
- Carabotti M, Scirocco A, Maselli MA, Severi C. The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Ann Gastroenterol. 2015 Apr-Jun;28(2):203-209. PMID: 25830558; PMCID: PMC4367209.
- Järbrink-Sehgal, E., & Andreasson, A. (2020). The gut microbiota and mental health in adults. Current Opinion in Neurobiology, 62, 102–114. https://doi.org/10.1016/j.conb.2020.01.016
- Nikolova VL, Smith MRB, Hall LJ, Cleare AJ, Stone JM, Young AH. Perturbations in Gut Microbiota Composition in Psychiatric Disorders: A Review and Meta-analysis. JAMA Psychiatry. 2021;78(12):1343–1354. doi:10.1001/jamapsychiatry.2021.2573
- Clapp M, Aurora N, Herrera L, Bhatia M, Wilen E, Wakefield S. Gut microbiota’s effect on mental health: The gut-brain axis. Clin Pract. 2017 Sep 15;7(4):987. doi: 10.4081/cp.2017.987. PMID: 29071061; PMCID: PMC5641835.
- North CS, Hong BA, Alpers DH. Relationship of functional gastrointestinal disorders and psychiatric disorders: implications for treatment. World J Gastroenterol. 2007 Apr 14;13(14):2020-7. doi: 10.3748/wjg.v13.i14.2020. PMID: 17465442; PMCID: PMC4319119.
- Haug TT, Mykletun A, Dahl AA. Are anxiety and depression related to gastrointestinal symptoms in the general population? Scand J Gastroenterol. 2002 Mar;37(3):294-8. doi: 10.1080/003655202317284192. PMID: 11916191.
- Peirce, J. M., & Alviña, K. (2019). The role of inflammation and the gut microbiome in depression and anxiety. Journal of Neuroscience Research, 97(10), 1223–1241. https://doi.org/10.1002/jnr.24476
- Yang B, Wei J, Ju P, et alEffects of regulating intestinal microbiota on anxiety symptoms: A systematic review General Psychiatry 2019;32:e100056. doi: 10.1136/gpsych-2019-100056