Gut-Brain Connection

The Gut–Brain Connection (Gut–Brain Axis)

Definition and Overview

The gut–brain axis (GBA) consists of bidirectional communication between the central and the enteric nervous system, linking emotional and cognitive centers of the brain with peripheral intestinal functions. Recent advances in research have described the importance of gut microbiota in influencing these interactions, and the interaction between microbiota and the GBA appears to be bidirectional — signaling from gut microbiota to brain and from brain to gut microbiota — by means of neural, endocrine, immune, and humoral links.

Insights into the gut–brain crosstalk have revealed a complex communication system that not only ensures the proper maintenance of gastrointestinal homeostasis, but is likely to have multiple effects on affect, motivation, and higher cognitive functions. In recognition of the central role of the microbiome in this network, researchers now frequently use the term microbiota–gut–brain axis (MGBA). In recent years, evidence has highlighted the pivotal role of the gut microbiota in modulating this axis, forming what is designated as the microbiota–gut–brain axis (MGBA).

Preclinical evidence has firmly established bidirectional interactions among the brain, the gut, and the gut microbiome. Candidate signaling molecules and at least three communication channels have been identified. Communication within this system is nonlinear, is bidirectional with multiple feedback loops, and likely involves interactions between different channels.

Body Systems Involved

Broadly defined, the gut–brain axis includes the central nervous system, neuroendocrine system, neuroimmune systems, the hypothalamic–pituitary–adrenal axis (HPA axis), sympathetic and parasympathetic arms of the autonomic nervous system, the enteric nervous system, vagus nerve, and the gut microbiota.

The Enteric Nervous System

The enteric nervous system (ENS), often referred to as the "second brain," is embedded within the walls of the gastrointestinal tract and contains over 500 million neurons that function independently to regulate gastrointestinal motility, secretion, and blood flow. The enteric nervous system operates semi-independently but remains in constant communication with the brain, allowing gut microbes to influence neural processes such as mood regulation, stress response, and neurodevelopment.

The Vagus Nerve

The microbiota, the gut, and the brain communicate through the microbiota–gut–brain axis in a bidirectional way that involves the autonomic nervous system. The vagus nerve (VN), the principal component of the parasympathetic nervous system, is a mixed nerve composed of 80% afferent and 20% efferent fibers. The VN, because of its role in interoceptive awareness, is able to sense microbiota metabolites through its afferents, transfer this gut information to the central nervous system where it is integrated in the central autonomic network, and then generate an adapted or inappropriate response.

A cholinergic anti-inflammatory pathway has been described through VN's fibers, which is able to dampen peripheral inflammation and to decrease intestinal permeability, thus very probably modulating microbiota composition. The VN, while crucial in various physiological processes, can become a double-edged sword by transmitting detrimental signals from an imbalanced microbiome to the brain in cases of dysbiosis.

The HPA Axis and Neuroendocrine Pathway

The imbalance of the microbiota will destroy the intestinal barrier tight junction protein, leading to the entry of inflammatory factors into the nervous system and causing cognitive impairment. The HPA axis is an endocrine communication pathway between the brain and the gut. Microorganisms can influence CNS processes bidirectionally via the vagus nerve and through modulation of the immune system, the hypothalamic–pituitary–adrenal (HPA) axis, and tryptophan metabolism, along with their ability to synthesize a number of neurotransmitters and produce metabolites, such as short-chain fatty acids (SCFAs), that possess neuroactive properties.

The Immune Pathway

Communications via the immune system occur through cytokines produced in the gut and can travel to the brain through the bloodstream. Gut infection, SIBO, and dysbiosis are associated with a disrupted gut barrier, overactivation of the inflammasome, and release of inflammatory cytokines leading to systemic inflammation. Blood–brain barrier (BBB) disruption from systemic inflammation initiates the neuroinflammatory response and alters homeostatic mechanisms.

Serotonin and the Gut

As specialized enteroendocrine cells, enterochromaffin (EC) cells produce up to 95% of total body serotonin and coordinate luminal and basolateral communication in the gastrointestinal tract. EC cells affect a broad range of gut physiological processes, such as motility, absorption, secretion, chemo/mechanosensation, and pathologies, including visceral hypersensitivity, immune dysfunction, and impaired gastrointestinal barrier function.

Approximately 90% of the body's serotonin is synthesized in the gut, predominantly by enterochromaffin cells. This gut-derived serotonin not only regulates local intestinal functions, such as peristalsis and secretion, but also exerts systemic effects by activating vagal afferent fibers. These fibers relay serotonergic signals to the nucleus tractus solitarius (NTS) in the brainstem, where they are processed and transmitted to higher brain regions.

Microbiota-derived SCFAs regulate the release of gut peptides from enteroendocrine cells and have been shown to regulate the synthesis of gut-derived serotonin from enterochromaffin cells, both of which in turn affect gut–brain hormonal communication.

The Gut Microbiota Itself

The gut microbiota plays a role in central nervous system functions (i.e., mood and psychiatric conditions associated with stress and memory) and is a central regulator of metabolism and appetite. Neuroactive compounds are released by bacteria such as γ-aminobutyric acid (GABA), serotonin, dopamine, and acetylcholine (ACh), and essentially act locally on the enteric nervous system.

How the Gut–Brain Connection Presents: Associated Conditions

Dysbiosis has been associated with altered gut–brain signaling and implicated in the pathophysiology of disorders ranging from irritable bowel syndrome to mood disorders and neurodegeneration. Dysbiosis — altered microbial composition and function — is implicated in the rising global burden of neurodegenerative (Alzheimer's, Parkinson's), psychiatric (depression, anxiety, autism spectrum disorder), functional gastrointestinal (IBS, functional dyspepsia), cardiovascular, and metabolic disorders (obesity, diabetes).

A perturbation of this axis is involved in the pathophysiology of gastrointestinal disorders such as irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD), which are biopsychosocial diseases. IBS can be seen as a "stress disease" and has been studied from different perspectives at virtually all levels of the gut–brain–microbiome axis. There is evidence for HPA axis and autonomic nervous system involvement, comorbidity of anxiety and depression, increased interoception, and altered neuronal pain processing.

With respect to neurodegeneration, the gut–brain axis theory proposed by Braak suggests that α-synuclein aggregation and misfolding in Parkinson's disease may begin in the ENS due to infection and inflammation, later spreading to the CNS and causing central neuropathy. Studies show that α-synuclein injected into the intestinal muscular layer translocates to the brain via vagus nerve fibers in a time-dependent manner, supporting the hypothesis that Parkinson's disease may originate in the gastrointestinal tract.

Contributing and Associated Factors

Compositional Factors: The Gut Microbiota

An individual's gut microbiota composition depends on the mode of delivery at birth, genetic predisposition, age, nutrition, physical activity, environmental factors, stress, infections, other diseases, and use of antibiotics. The gut microbiota is composed of four major phyla — Bacteroidetes, Firmicutes, Proteobacteria, and Actinobacteria — and two minor phyla, Verrucomicrobia and Fusobacteria.

Psychological Stress

Acute gastroenteritis, antibiotics, and stress are dominant risk factors for intestinal dysbiosis and subsequent IBS in both adults and children. An increase in inflammation in the bowel wall may result in a chronic, subclinical, low-grade inflammation that is sufficient to alter neuromuscular and epithelial cell function. The contribution of such a microbiota–immune interaction to stress-associated pathologies is supported by the observation that exposure to repeated stress affects the gut microbiota in a manner that correlates with changes in levels of pro-inflammatory cytokines.

Early Life Factors

An important factor for the development of IBS is early-life stressors, especially maternal separation, which may have long-term effects on the microbiota. In animal studies, stress-induced changes in physiology resulted in dysbiosis, and the dysbiotic microbiota was required for stress-induced anxiety-like behavior to manifest.

Antibiotic Exposure

Antibiotic exposure during the first year of life is associated with higher rates of behavioural problems, depressive symptoms, and neurocognitive decline later in life. Other reports have documented psychiatric side effects, including anxiety and major depression, in patients receiving antibiotics, suggesting that dysbiosis can causally contribute to mental health disorders. Preclinical research confirms that antibiotic-induced dysbiosis can provoke anxiety- and depression-like behaviours in rodents, and fecal microbiota transplantation from patients with depression into animal models induced depressive symptoms and metabolic changes.

Dietary Patterns

Diet, stress, antibiotics, and environment significantly alter gut microbiota composition, for example reducing diversity and shifting the Firmicutes/Bacteroidetes ratio. Sedentary work, lack of exercise, a Western high-carbohydrate diet, and processed food are additional well-established risk factors for IBS.

Sex and Hormones

IBS is almost twice as prevalent in women, with the relative risk of IBS in women compared with men being 1.67 in a study of 188,229 subjects, pointing to a hormonal relationship.

Intestinal Permeability ("Leaky Gut")

The disruption of the brain–gut axis — the major bidirectional communication pathway between the brain and the gastrointestinal system, which incorporates both afferent and efferent signals involving neuronal, hormonal, and immunologic pathways — can result in sequelae such as chronic dysfunction of the gastrointestinal system and disability. The imbalance of the microbiota will destroy the intestinal barrier tight junction protein, leading to the entry of inflammatory factors into the nervous system and causing cognitive impairment.

Nutrients, Herbs, and Natural Ingredients

Short-Chain Fatty Acids (SCFAs)

The SCFAs acetate, propionate, and butyrate are the main metabolites produced in the colon by bacterial fermentation of dietary fibers and resistant starch. SCFAs, the main metabolites produced in the colon by bacterial fermentation of dietary fibers and resistant starch, are speculated to play a key role in neuro-immunoendocrine regulation.

Butyrate can inhibit histone deacetylase, modulate gene expression, influence immune functionality, and regulate tight junction integrity, supporting the idea of its role in gut barrier preservation. Research indicates that butyrate can alleviate neurological disorders, including Alzheimer's, Parkinson's, autism spectrum disorder, and Huntington's disease, by reducing neuroinflammation, enhancing neurotransmitter modulation, and improving histone acetylation.

Evidence strength: SCFAs are speculated to play a key role in neuro-immunoendocrine regulation; however, the underlying mechanisms through which SCFAs might influence brain physiology and behavior have not been fully elucidated. Most supportive data remain preclinical or mechanistic. Medical literature extensively documents the supplementation of SCFAs, particularly butyrate, in the treatment of gastrointestinal, metabolic, cardiovascular, and gut-brain-related disorders, but large-scale human clinical trials are limited.

Dietary Fiber and Resistant Starch (Prebiotics)

The gastrointestinal tract is home to trillions of diverse microorganisms, which play a pivotal role in breaking down undigested foods such as dietary fibers. Through the fermentation of these food components, SCFAs such as acetate, propionate, and butyrate are produced, offering numerous health benefits to the host. The production and absorption of these SCFAs occur through various mechanisms within the human intestine, contingent upon the types of dietary fibers reaching the gut and the specific microorganisms engaged in fermentation.

A 3-month fiber-rich diet in patients with type 2 diabetes showed an increase in SCFA-producing bacteria F. prausnitzii and A. muciniphila, as well as a decrease in glucose, total and LDL cholesterol, free fatty acids, and hemoglobin A1c (HbA1c), suggesting that long-term adherence to a high-fiber diet might improve dyslipidemia, glycemic control, and inflammation by increasing SCFA-producing bacteria.

Tryptophan

Microorganisms can influence CNS processes via modulation of tryptophan metabolism, the precursor to serotonin. Tryptophan metabolites represent one class of microbial metabolites — alongside SCFAs and bile acids — that modulate neuroinflammation, blood–brain barrier integrity, and broader neuropathological processes. Specific microbial metabolites, such as indole derivatives from tryptophan metabolism, can counteract NF-κB activation and provide neuroprotective effects.

Evidence strength: The tryptophan–serotonin axis is well-established mechanistically and supported by multiple preclinical and observational studies. Interventional human trials targeting tryptophan specifically for gut–brain outcomes remain limited and preliminary.

Omega-3 Fatty Acids

Bioactive compounds like prebiotics, omega-3 fatty acids, and polyphenols exhibit neuroprotective effects by modulating gut microbiota and reducing neuroinflammation. An open-label and randomized trial increased gut microbial SCFAs indirectly by using an omega-3 polyunsaturated fatty acid supplement drink or capsule, which led to an increase in SCFA-producing bacteria (e.g., Bifidobacterium, Roseburia, and Lactobacillus) in humans, indicating a promising approach to improving gut dysfunction and depressive symptoms.

Evidence strength: Human trials using omega-3 supplementation show positive effects on SCFA-producing bacteria and inflammatory markers, but direct gut–brain outcome trials are preliminary. Overall, the evidence is promising but requires larger confirmatory studies.

Probiotics and Psychobiotics

Certain probiotic strains — often termed "psychobiotics" — can modulate the gut microbiota composition and metabolic activity, enhancing the production of neuroactive compounds such as GABA, serotonin precursors, and SCFAs. Probiotics indirectly alter CNS function by producing metabolites that influence serotonin levels, brain-derived neurotrophic factor (BDNF), dopamine, and GABA.

Scientific Evidence — Depression: A systematic review of randomized clinical trials conducted from January 2000 to December 2023 examined the efficacy of psychobiotics in adults with psychiatric and cognitive disorders. Out of the 51 studies involving 3,353 patients (half of whom received psychobiotics), there was a notably high measurement of effectiveness specifically in the treatment of depression symptoms. Most participants were older and female, with treatments commonly utilizing strains of Lactobacillus and Bifidobacteria over periods ranging from 4 to 24 weeks.

A 2023 meta-analysis of 13 RCTs with 786 participants estimated the effectiveness of pre-, pro-, and synbiotics on clinical depression symptoms and found an overall small effect-size reduction in depression severity (standardized mean difference [SMD] = −0.34; 95% CI: −0.45, −0.22) in favor of the treatment group compared with placebo controls. Subgroup analysis revealed that only probiotics — both single and multiple strain — were associated with significant, small effect-size reductions in depression severity.

Clinical trials investigating strains such as Lactobacillus rhamnosus, Bifidobacterium longum, Lactobacillus gasseri, and multi-strain formulations have demonstrated strain- and context-specific effects on psychological and physiological outcomes. While some studies reported improvements in mood, anxiety, sleep quality, and cognitive performance, others showed limited effects, particularly in healthy populations with low baseline stress levels, reflecting the challenges of translating preclinical findings into clinical applications in humans.

Limitations: The variability in treatment approaches and clinical presentations limits the comparability and generalization of findings. This underscores the need for more personalized treatment optimization and a deeper investigation into the mechanisms through which psychobiotics act. Probiotic supplements are thought to have largely positive effects on mental health when taken in sufficient amounts; however, despite extensive research, there is a lack of consistent findings on the effects of probiotics on anxiety and depression and the associated microbiome alterations.

Curcumin (Curcuma longa)

Traditional Use: Curcumin (CUR) is a lipophilic natural polyphenol isolated from the rhizome of turmeric. Studies have proposed that CUR possesses a variety of biological activities. Turmeric has been used for centuries in Ayurvedic and traditional Chinese medicine as an anti-inflammatory and digestive agent.

Scientific Evidence: It is possible that curcumin could exert direct regulative effects primarily in the gastrointestinal tract, where high concentrations are present after oral administration. A working hypothesis that could explain the neuroprotective role of curcumin despite its limited bioavailability is that it acts indirectly on the CNS by influencing the microbiota–gut–brain axis — a complex bidirectional system in which the microbiome and its composition represent a factor which preserves and determines brain "health." Curcumin and its metabolites might provide benefit by restoring dysbiosis of the gut microbiome.

Curcumin and its metabolites can have health benefits by eliminating intestinal microflora dysbiosis. In addition, curcumin undergoes enzymatic modifications by bacteria, forming pharmacologically more active metabolites than their parent compound, curcumin.

The gut–brain axis has attracted increasing attention owing to its regulatory effect on dysbiosis and a wide range of related diseases. Several types of nutrients, such as curcumin, have been proposed as regulators of the dysbiotic state, and preclinical experiments have suggested that curcumin is not only beneficial but also safe.

Evidence strength: A discrepancy exists between the well-documented pharmacological activities that curcumin seems to possess in vivo and its poor aqueous solubility, bioavailability, and pharmacokinetic profiles that should limit any therapeutic effect. Most human evidence comes from small trials; gut–brain specific human clinical data on curcumin remain preliminary.

Ginkgo biloba, Ginseng, and Other Traditional Neurological Herbs

Traditional Use: Herbal medicine has been used for centuries to treat human diseases, including neurodegenerative diseases.

Scientific Evidence: The use of herbal medicine formulations such as Ginkgo biloba, ginseng, and Polygala tenuifolia has demonstrated promising effects in preclinical studies. These herbs contain active metabolites that, once biotransformed by the gut microbiota, can cross the blood–brain barrier and exert therapeutic effects directly within the CNS.

Evidence strength: The evidence for Ginkgo biloba, ginseng, and related herbs acting specifically via the gut–brain axis is primarily preclinical. Clinical trials remain limited and largely exploratory.

German Chamomile (Matricaria chamomilla)

Traditional Use: German chamomile (Matricaria chamomilla L.) is a ubiquitous annual plant with a rich history in traditional European medicine, and has been a cornerstone of herbal remedies for centuries, particularly for its calming, anti-inflammatory, and spasmolytic effects on the gastrointestinal tract.

Scientific Evidence: Iberogast (STW 5) is a well-studied herbal preparation that has been tested in numerous clinical trials. It is a herbal medicine containing extracts from nine plants, including chamomile flowers. Chamomile has demonstrated GI-spasmolytic activity, and Iberogast has clinical evidence for functional dyspepsia and IBS. Chamomile preparations are commonly used to support the treatment of various human ailments, such as allergic rhinitis, inflammatory conditions, muscle cramps, menstrual irregularities, insomnia, and peptic ulcers. Chamomile extracts are used most frequently for oral cavity inflammatory conditions and in the treatment of stomach inflammations.

Evidence strength: Chamomile's role in gastrointestinal spasm is supported by traditional use and the multi-herb preparation Iberogast (with several clinical trials). Studies specifically isolating chamomile's effect on the gut–brain axis are limited.

Ashwagandha (Withania somnifera)

Traditional Use: Withania somnifera is a plant commonly referred to as ashwagandha. The plant root has been used for its health-promoting effects. In Ayurveda, ashwagandha is classified as a rasayana (rejuvenating tonic) traditionally used for stress, debility, and cognitive function.

Scientific Evidence: Research supports the use of W. somnifera to help with stress and sleep. Ashwagandha combined with okra (Abelmoschus esculentus) as a dual-herb supplement has shown promise in improving both GI regularity and mood by modulating the gut–brain axis. This combination has demonstrated adaptogenic function and has been shown to increase serotonin.

Evidence strength: Ashwagandha's stress-reducing effects have support from small-to-moderate-size RCTs. Its specific modulation of the gut–brain axis is preliminary and often studied in combination preparations rather than in isolation.

Polyphenols (General)

Certain dietary compounds, such as polyphenols found in plant-based foods, have been shown to support brain function by modulating gut bacteria and reducing oxidative stress. Microbial modulation of host gene expression via epigenetic mechanisms, including microRNAs, adds another layer of complexity to how plant-derived polyphenols may act through the microbiome.

Evidence strength: Evidence for dietary polyphenols (resveratrol, quercetin, catechins, etc.) acting on the gut–brain axis is largely mechanistic and preclinical. Human interventional trials are few and often underpowered.

Dietary and Lifestyle Factors

The Mediterranean Diet

The Mediterranean diet — characterized by high intake of fiber, polyphenols, omega-3 fatty acids, and fermented foods — promotes microbial diversity and increases the abundance of beneficial taxa such as Bifidobacterium and Lactobacillus, as well as SCFA-producing species such as Faecalibacterium prausnitzii.

A transversal study with 31 healthy individuals showed that those following a 6-month Mediterranean diet presented higher propionate and butyrate concentrations in feces, and higher levels of Bifidobacterium and Faecalibacterium, compared to those following a lower-fiber diet.

Taken together with current clinical evidence, these mechanisms help explain why adherence to the Mediterranean diet may translate into more favorable microbial profiles and the cognitive benefits observed in recent cohorts and systematic reviews.

Fermented Foods

Preliminary placebo-controlled human studies have shown that oral probiotic microbes can decrease anxiety, diminish perceptions of stress, and improve mental outlook. The consumption of fermented foods, berries, nuts, and probiotic supplements improves working memory and attention across different populations.

High-Fat and Ultra-Processed Western Diets

Factors that trigger dysbiosis, such as high fat consumption, could act by promoting the production of pro-inflammatory bacterial metabolites. Recent research has underscored the significant role of diet in modulating the gut–brain axis, with attention to how specific dietary patterns can impact anxiety and depression, particularly when linked to disorders of gut–brain interaction like IBS.

Physical Activity

An individual's gut microbiota composition depends on, among other factors, nutrition and physical activity. Sedentary work and lack of exercise are additional well-established risk factors for IBS and, by extension, gut–brain axis dysregulation.

Stress Management and Psychological Factors

The GBA framework also provides insight into the connection between psychiatric and GI disorders, with mood disorders such as anxiety and depression highly prevalent among patients with GI disorders like IBS. Recent research points to a role of intestinal microbiota in visceral hypersensitivity, anxiety, and depression. Increased disease reactivity to psychological stress has been described. These observations underscore that managing psychological stress through behavioral interventions may, through the GBA, exert downstream effects on gastrointestinal health and microbiome composition.

Age and the Gut–Brain Axis

Other factors that may exacerbate existing gut–brain dysregulation include poor diet and physiological changes from aging, like increased inflammatory response, decreased neurotransmitters, and increased oxidative stress.

Personalized Nutrition

Emerging research highlights the role of personalized nutrition in mental health, emphasizing the need for tailored dietary recommendations based on an individual's microbiome composition. The heterogeneity in treatment responses across studies reflects fundamental individual differences in microbiome composition, host genetics, and environmental factors.

Summary of Evidence Levels

• Well-established (human clinical and mechanistic evidence): The anatomical and physiological existence of the gut–brain axis; the central role of the vagus nerve, ENS, HPA axis, and serotonin in gut–brain communication; the impact of dysbiosis on GI and neuropsychiatric conditions; dietary fiber and prebiotic fermentation to SCFAs; Mediterranean diet associations with favorable microbiome profiles.
• Supported by clinical trials with noted limitations: Probiotic/psychobiotic interventions for depression (small-to-moderate effect sizes; high heterogeneity across studies; strain- and population-specific outcomes); omega-3 fatty acids for microbiota modulation.
• Preliminary or largely preclinical: Curcumin acting on the gut–brain axis via microbiome modulation; specific polyphenols; ginkgo, ginseng, and other traditional botanicals acting through MGBA pathways; butyrate supplementation in neurological disorders.
• Traditional use with limited human interventional data: German chamomile (GI spasmolytic in combination products); ashwagandha (adaptogenic stress support, with some human trial evidence); fermented foods as delivery vehicles for live cultures.

References

• Carabotti M, et al. (2015). The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Annals of Gastroenterology. PMC4367209.
• Wikipedia: Gut–brain axis (overview and references to primary sources)
• PMC12440273 — Role of the gut-brain axis in neurological diseases: Molecular connections and therapeutic implications (Review). PMC, 2025.
• Mayer EA, Nance K, Chen S. (2022). The Gut–Brain Axis. Annual Review of Medicine, 73:439–453.
• PMC12293201 — Rewiring the Brain Through the Gut: Insights into Microbiota–Nervous System Interactions. PMC, 2025.
• Frontiers in Microbiomes — The gut–brain connection: microbes' influence on mental health and psychological disorders. 2025.
• PMC5808284 — The Vagus Nerve at the Interface of the Microbiota-Gut-Brain Axis. Frontiers in Neuroscience, 2018.
• PMC7589356 — Gut–Brain Axis: Role of Gut Microbiota on Neurological Disorders and How Probiotics/Prebiotics Modulate Microbial and Immune Pathways. PMC, 2020.
• PMC5046167 — Irritable bowel syndrome, the microbiota and the gut-brain axis. PMC, 2016.
• PMC11510627 — Gut–Brain Axis and Psychopathology: Exploring the Impact of Diet with a Focus on the Low-FODMAP Approach. PMC, 2024.
• PMC5860136 — Intestinal microbiome-gut-brain axis and irritable bowel syndrome. PMC, 2018.
• PMC4879184 — From gut dysbiosis to altered brain function and mental illness: mechanisms and pathways. PMC, 2016.
• PMC4458706 — Gut-microbiota-brain axis and effect on neuropsychiatric disorders with suspected immune dysregulation. PMC, 2015.
• PMC10867509 — Exploring the serotonin-probiotics-gut health axis: A review of current evidence and potential mechanisms. PMC, 2024.
• PMC11818468 — Interaction of the Vagus Nerve and Serotonin in the Gut–Brain Axis. PMC, 2025.
• PMC9274469 — Enterochromaffin Cells–Gut Microbiota Crosstalk: Underpinning the Symptoms, Pathogenesis, and Pharmacotherapy in Disorders of Gut-Brain Interaction. PMC, 2022.
• PMC10455396 — The Impact of Microbiota on the Gut–Brain Axis: Examining the Complex Interplay and Implications. PMC, 2023.
• PMC11085935 — Effectiveness of Psychobiotics in the Treatment of Psychiatric and Cognitive Disorders: A Systematic Review of RCTs. PMC, 2024.
• PMC12166186 — Effects of Prebiotics and Probiotics on Symptoms of Depression and Anxiety: Systematic Review and Meta-analysis of RCTs. PMC, 2024.
• PMC10893170 — Probiotics' Effects in the Treatment of Anxiety and Depression: A Comprehensive Review of 2014–2023 Clinical Trials. PMC, 2024.
• Frontiers in Microbiology — Psychobiotics in mental health: insights from human clinical trials via the gut-brain axis. 2026.
• PMC7005631 — The Role of Short-Chain Fatty Acids From Gut Microbiota in Gut-Brain Communication. PMC, 2020.
• PMC7551052 — Interaction between Gut Microbiota and Curcumin: A New Key of Understanding for the Health Effects of Curcumin. PMC, 2020.
• PMC7037549 — Mutual Two-Way Interactions of Curcumin and Gut Microbiota. PMC, 2020.
• PMC6835970 — Curcumin, Gut Microbiota, and Neuroprotection. PMC, 2019.
• PMC10830735 — Herbal medicine and gut microbiota: exploring untapped therapeutic potential in neurodegenerative disease management. PMC, 2024.
• PMC11319522 — Addressing GI Health Through the Bidirectional Modulation of the Gut-Brain Axis With Herbal Extracts: A Narrative Review. PMC, 2024.
• PMC12652186 — Medicinal Plants for a Healthy Gut Microbiome: Scientific Insights into Modern Herbal Applications. PMC, 2025.
• PMC3904694 — Fermented foods, microbiota, and mental health: ancient practice meets nutritional psychiatry. PMC, 2014.
• PMC8007165 — The role of short-chain fatty acids in the interplay between gut microbiota and diet in cardio-metabolic health. PMC, 2021.
• PMC10882305 — Gut microbiota-derived short-chain fatty acids and depression: deep insight into biological mechanisms and potential applications. PMC, 2024.
• PMC12071848 — Could a Mediterranean Diet Modulate Alzheimer's Disease Progression? The Role of Gut Microbiota and Metabolite Signatures in Neurodegeneration. PMC, 2025.
• PMC10936641 — A modified Mediterranean-style diet enhances brain function via specific gut-microbiome-brain mechanisms. PMC, 2024.
• PMC11853140 — Gut–Brain Axis and Brain Microbiome Interactions from a Medical Perspective. PMC, 2025.
• PMC12296502 — Short-chain fatty acids mediate enteric and central nervous system homeostasis in Parkinson's disease. PMC, 2025.
• PMC12925874 — The Intestinal Cues Promoting Serotonin Release From the Human Gut. PMC, 2025.
• PMC12689588 — Transforming mental health: the future of personalized psychobiotics in anxiety and depression therapy. PMC, 2025.
• Frontiers in Microbiology — Brain-gut-microbiota axis: a review on bidirectional regulatory mechanisms and disease interactions. 2026.
• PMC12645147 — Restoring Gut-brain Function by Medicinal Herbs Offering Neuroprotection through Suppressing Inflammatory Pathways: A Systematic Review. PMC, 2025.
• PMC12366197 — The Gut-Brain Axis and Mental Health: How Diet Shapes Our Cognitive and Emotional Well-Being. PMC, 2025.
• PMC11052165 — The Modulatory Effects of Curcumin on the Gut Microbiota: A Potential Strategy for Disease Treatment and Health Promotion. PMC, 2024.
• PMC12029953 — Beyond the Gut: Unveiling Butyrate's Global Health Impact Through Gut Health and Dysbiosis-Related Conditions: A Narrative Review. PMC, 2025.
• Park S, et al. (2023). The Effect of Curcumin on the Gut-Brain Axis: Therapeutic Implications. Journal of Neurogastroenterology and Motility.