Effects of SIBO on Mental Health
1. Gut Microbiome
2. Gut-Brain Axis
2.1 The Gut-Brain
2.2 Gut Microbiome and Mental Health
2.3 Bacterial Metabolites and Mental Health
3. SIBO and Mental Health
3.1 SIBO and Serotonin
3.2 SIBO Therapy and Mental Health
1. Gut Microbiome
The gut microbiome refers to the microorganisms living in the intestines. It consists of bacteria, archaea, and fungi and is a natural part of the human body. The composition of the gut microbiome varies from person to person, and certain compositions are considered more beneficial or detrimental. A microbiome that deviates from a so called healthy norm may be associated with the presence of certain diseases. Gut bacteria perform numerous functions, including training and influencing the system, producing metabolites like short chain fatty acids (SCFAs) and vitamins, defending against pathogens, and more.
2. Gut-Brain Axis
Everyone has experienced it: a gut feeling. In some situations, we trust our gut more than the logical arguments presented by our brain. But is there more to these decisions than just an ominous sensation?
2.1 The Gut-Brain
The gut and the brain are in constant communication. The gut is not only responsible for digesting food but also houses a significant portion of the immune system and has its own nervous system. This enteric nervous system (ENS) is autonomous, meaning we cannot consciously control it. The ENS regulates functions such as gut motility and gastrointestinal blood flow. The brain, on the other hand, is part of the central nervous system (CNS). The CNS and ENS influence each other and are in continuous communication.
2.2 Gut Microbiome and Mental Health
An essential component of our gut is the gut microbiome. An altered gut flora (dysbiosis) has been associated with neurological disorders such as depression or autism (1). Additionally, it is known that the use of antibiotics can increase the risk of depression (2). A study from 2016 found a connection between the microbiome and the development of depression (3). Researchers transferred the microbiome from depressed individuals into healthy rats and observed that these rats subsequently exhibited depressive symptoms (3).
2.3 Bacterial Metabolites and Mental Health
But how do bacteria in our gut influence our brain and, consequently, our mood? The gut flora produces substances such as GABA (gamma-aminobutyric acid) and serotonin, which play a role in gut-brain communication. GABA and serotonin are important neurotransmitters. Certain bacteria, such as Bifidobacterium and Lactobacillus, can produce GABA (4,5). The presence of Roseburia intestinalis in the gut has been associated with increased serotonin levels in the brain (6).
3. SIBO and Mental Health
SIBO stands for “small intestinal bacterial overgrowth,” which refers to an abnormal bacterial overgrowth in the small intestine. In a healthy state, the small intestine, unlike the colon, is only sparsely populated with bacteria. SIBO describes the pathological overgrowth of bacteria in the small intestine. This dysbiosis can lead to an increased presence of bacterial metabolites and toxins, which can affect the gut-brain axis and negatively impact mental health.
3.1 SIBO and Serotonin
SIBO has been associated with depression and anxiety disorders (7). The reason for this appears to be a change in tryptophan-serotonin metabolism caused by small intestinal bacterial overgrowth (8). Tryptophan can be metabolized to serotonin in just a few steps. Serotonin is sometimes referred to as the “happiness hormone” because it plays a role in processing emotions in the brain. An imbalance in serotonin levels has been linked to depression and anxiety disorders.
3.2 SIBO Therapy and Mental Health
When SIBO is treated with an individually tailored therapy, an improvement in psychological symptoms may occur (9,10). SIBO therapy can include various treatments, such as antibiotics or probiotics. However, SIBO treatment should always be carried out in collaboration with a physician.
References
- Zhou L, Foster JA. Psychobiotics and the gut-brain axis: in the pursuit of happiness. Neuropsychiatr Dis Treat. 2015 Mar 16;11:715-23. doi: 10.2147/NDT.S61997. PMID: 25834446; PMCID: PMC4370913.
- Lee J, Park SJ, Choi S, Chang J, Park YJ, Jeong S, Son JS, Lee G, Ahn JC, Kim JA, Park SM. Antibiotic exposure and depression incidence: A cohort study of the Korean population. Psychiatry Res. 2024 May 29;339:115992. doi: 10.1016/j.psychres.2024.115992. Epub ahead of print. PMID: 38875919.
- Kelly JR, Borre Y, O’ Brien C, Patterson E, El Aidy S, Deane J, Kennedy PJ, Beers S, Scott K, Moloney G, Hoban AE, Scott L, Fitzgerald P, Ross P, Stanton C, Clarke G, Cryan JF, Dinan TG. Transferring the blues: Depression-associated gut microbiota induces neurobehavioural changes in the rat. J Psychiatr Res. 2016 Nov;82:109-18. doi: 10.1016/j.jpsychires.2016.07.019. Epub 2016 Jul 25. PMID: 27491067.
- Zou XZ, Gong LC, Li TT, Lv SY, Wang J. Optimization of fermentation conditions for the production of γ-aminobutyric acid by Lactobacillus hilgardii GZ2 from traditional Chinese fermented beverage system. Bioprocess Biosyst Eng. 2024 Jun;47(6):957-969. doi: 10.1007/s00449-024-03028-x. Epub 2024 May 8. PMID: 38717593.
- Li J, Li Y, Zhao J, Li L, Wang Y, Chen F, Li Y, Cheng R, He F, Ze X, Shen X. Effects of Bifidobacterium breve 207-1 on regulating lifestyle behaviors and mental wellness in healthy adults based on the microbiome-gut-brain axis: a randomized, double-blind, placebo-controlled trial. Eur J Nutr. 2024 Jun 13. doi: 10.1007/s00394-024-03447-2. Epub ahead of print. PMID: 38869657.
- Zhou M, Fan Y, Xu L, Yu Z, Wang S, Xu H, Zhang J, Zhang L, Liu W, Wu L, Yu J, Yao H, Wang J, Gao R. Microbiome and tryptophan metabolomics analysis in adolescent depression: roles of the gut microbiota in the regulation of tryptophan-derived neurotransmitters and behaviors in human and mice. Microbiome. 2023 Jun 30;11(1):145. doi: 10.1186/s40168-023-01589-9. PMID: 37386523; PMCID: PMC10311725.
- Kossewska J, Bierlit K, Trajkovski V. Personality, Anxiety, and Stress in Patients with Small Intestine Bacterial Overgrowth Syndrome. The Polish Preliminary Study. Int J Environ Res Public Health. 2022 Dec 21;20(1):93. doi: 10.3390/ijerph20010093 . PMID: 36612414; PMCID: PMC9819554.
- Chojnacki C, Popławski T, Konrad P, Fila M, Chojnacki J, Błasiak J. Serotonin Pathway of Tryptophan Metabolism in Small Intestinal Bacterial Overgrowth-A Pilot Study with Patients Diagnosed with Lactulose Hydrogen Breath Test and Treated with Rifaximin. J Clin Med. 2021 May 12;10(10):2065. doi: 10.3390/jcm10102065. PMID: 34065903; PMCID: PMC8150299.
- Chojnacki C, Popławski T, Konrad P, Fila M, Błasiak J, Chojnacki J. Antimicrobial treatment improves tryptophan metabolism and mood of patients with small intestinal bacterial overgrowth. Nutr Metab (Lond). 2022 Sep 27;19(1):66. doi: 10.1186/s12986-022-00700-5. PMID: 36167589; PMCID: PMC9513933.
- Chojnacki C, Konrad P, Błońska A, Medrek-Socha M, Przybylowska-Sygut K, Chojnacki J, Poplawski T. Altered Tryptophan Metabolism on the Kynurenine Pathway in Depressive Patients with Small Intestinal Bacterial Overgrowth. Nutrients. 2022 Aug 6;14(15):3217. doi: 10.3390/nu14153217. PMID: 35956393; PMCID: PMC9370164.
