Mushrooms and the Gut-Brain Axis: Mood and Cognition

Gut-Brain Axis Research

90%

of the body's serotonin is produced in the gut, not the brain. Mushroom polysaccharides feed the bacteria most involved in this production, making the gut-brain axis a central pathway for their effects on mood and cognition.

Yao et al., Sci Rep, 2021; Cha et al., Neurosci Biobehav Rev, 2024

2023 RCT

Lion's mane improved cognition and reduced stress in a double-blind trial

5% diet

Agaricus mushrooms prevented brain oxidative stress in mice (2022)

3 channels

vagus nerve, immune signaling, neurotransmitter precursors

Yao et al., Sci Rep, 2021; Cha et al., Neurosci Biobehav Rev, 2024

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Most of the body's serotonin is not produced in the brain. Roughly 90% of it is synthesized in the gut, by cells stimulated largely by bacteria living in the intestine. This is the biological foundation of the gut-brain axis: the two-way communication network linking gut bacteria to mood, cognition, and stress response. Research on mushrooms and the gut-brain axis has accelerated in recent years, pointing toward a specific mechanism. Mushroom polysaccharides feed the gut bacteria most involved in neurotransmitter production and neuroprotection, through pathways that most readers have never seen explained and most competitor articles never cite.

This article examines what that research shows and what it hasn't yet established. For the upstream picture of how mushrooms modulate gut bacteria, how mushrooms feed your gut bacteria provides the full microbiota context.

What the Gut-Brain Axis Actually Is (And Why Serotonin Starts in the Gut)

The gut and the brain communicate constantly through three distinct channels. Understanding each one is necessary for understanding why mushrooms can have brain effects that run through the digestive system.

The first channel is the vagus nerve, the longest nerve in the body. It runs from the brainstem through the chest and into the abdomen, forming a direct physical link. Signals travel in both directions: gut bacteria can activate vagal pathways that reach the brain within seconds, without any chemical entering the bloodstream.

The second channel is immune signaling. The gut houses roughly 70% of the body's immune cells. When the gut microbial community shifts toward more inflammatory species and fewer beneficial ones, immune cells in the gut wall detect that change and release inflammatory messengers called cytokines. Those cytokines circulate to the brain, where they influence mood, motivation, and cognitive function. Chronically elevated pro-inflammatory cytokines are associated with depression, fatigue, and reduced executive function.

The third channel is neurotransmitter production. The gut wall contains specialized cells (enterochromaffin cells) that produce serotonin in response to signals from gut bacteria. About 90% of the body's total serotonin is synthesized here, not in the brain. Gut bacteria also produce precursors and signaling compounds for GABA, dopamine, and other neurotransmitters. Short-chain fatty acids (SCFAs) produced by bacterial fermentation can cross the blood-brain barrier directly, influencing neuroinflammation and the production of brain-derived neurotrophic factor (BDNF), a protein critical for neuron maintenance and cognitive function.

A 2024 review by Cha and colleagues in Neuroscience and Biobehavioral Reviews synthesized the full landscape of mushrooms' effects on mood and neurocognitive health, covering both direct brain effects (compounds crossing the blood-brain barrier) and gut-mediated effects across the lifespan.^[1] It is the most current and comprehensive review in a top-tier neuroscience journal. The gut-brain axis is one of its central conclusions.

How Mushrooms Connect to the Gut-Brain Axis

Mushroom polysaccharides have a property that makes them relevant to this axis: human digestive enzymes cannot break them down. They arrive in the colon intact and serve as food for bacteria. This is the prebiotic function.

A comprehensive 2017 review by Jayachandran and colleagues catalogued which mushroom species affect which bacterial populations and what health outcomes follow.^[2] The consistent finding: edible mushrooms enrich Bifidobacterium and Lactobacillus species. These are among the most studied bacteria for both neurotransmitter production and gut barrier integrity. Their depletion is associated with depression and anxiety in the microbiome literature.

A 2020 review by Yin and colleagues provided more precision: mushroom polysaccharides specifically increase SCFA-producing bacteria, not just any beneficial species.^[3] That distinction is meaningful for the gut-brain connection. SCFA-producing bacteria generate butyrate, propionate, and acetate as byproducts of fiber fermentation. Butyrate is the one most relevant to brain function: it crosses the blood-brain barrier and reduces neuroinflammation while supporting BDNF production.

A 2020 review by Liu and colleagues established the mechanistic link between specific mushroom bioactive components (beta-glucans, chitin, polysaccharides) and the downstream health outcomes they produce via gut microbiota.^[4]

The indirect pathway from mushrooms to brain looks like this: mushroom polysaccharides feed Bifidobacterium and SCFA-producing bacteria, which ferment those fibers into butyrate, which crosses into the brain, where it reduces inflammation and upregulates neuroplasticity factors.

There is also a direct pathway operating in some species. Lion's mane contains compounds called hericenones and erinacines that cross the blood-brain barrier independently and stimulate nerve growth factor (NGF) production without any bacterial intermediary. This cluster's focus is the indirect route. The two pathways are not competing explanations; both may operate simultaneously when someone consumes lion's mane, with the relative contribution of each not yet established.

For the species-level prebiotic specifics, which mushrooms are the best prebiotics covers that evidence. For the deeper mechanistic pathway from gut fiber to brain, how mushroom prebiotics influence brain function through the gut covers it in full.

Reishi, Gut Bacteria, and the Serotonin Pathway

The most direct evidence that a specific mushroom produces a brain effect through gut bacteria comes from a 2021 study by Yao and colleagues.^[5] They tested Ganoderma lucidum (Reishi) for its sleep-promoting effects in mice and designed the study specifically to isolate the mechanism.

The result was specific: Reishi promotes sleep through a gut microbiota-dependent serotonin pathway. When the researchers disrupted the gut microbiota, the sleep effect disappeared. When the microbiota was restored, the effect returned. The bacteria most involved included Bifidobacterium longum, a species with documented serotonin-related activity in the gut.

This finding matters beyond sleep. It provides the clearest experimental proof of the mechanism: Reishi is not acting like a sedative drug crossing into the brain. It is feeding specific gut bacteria that produce serotonin-pathway signals, and those signals reach the brain through the gut-brain axis. Remove the bacteria, remove the effect.

No consumer mushroom publication has described the mechanism this way. The Yao study is cited nowhere in the competitor content reviewed for this article. The standard claim ("Reishi promotes sleep") is correct but explanatorily empty. The gut microbiota-dependent serotonin pathway is the actual story.

For more on serotonin and dopamine pathways specifically in lion's mane research, how lion's mane affects serotonin and dopamine pathways covers that species in depth.

White Button Mushrooms and Brain Oxidative Stress: The 2022 Study

One of the most clinically relevant findings in gut-brain axis mushroom research involves the most ordinary mushroom in a grocery store.

A 2022 study by García-Sanmartín and colleagues tested diets containing 5% Agaricus bisporus (white button and Portobello mushrooms) in stressed mice.^[6] The experimental diet was not a concentrated extract; it was a realistic proportion of mushrooms as food.

The result: the mushroom diet significantly prevented the brain oxidative stress markers that develop under chronic psychological stress. Specifically, it blocked the upregulation of IL-6 (a pro-inflammatory cytokine that rises in stressed brains), Nox-2, and Hmox-1 genes, and prevented the depletion of antioxidant enzyme activity (catalase and superoxide dismutase) and excess lipid peroxidation in brain tissue.

The mechanism was traced back to gut bacteria. The mushroom-fed animals showed increased populations of Akkermansiaceae and Tannerellaceae, both SCFA-producing bacterial families. The neuroprotective effect flowed through those bacteria and their fermentation products.

The significance of this study is twofold. First, the dose was realistic rather than pharmacological. Second, the mushroom was white button and Portobello, not a specialized medicinal species. The same gut-brain axis pathway through SCFA-producing bacteria operates with a common dietary food, not just high-dose lion's mane or Reishi extracts.

A 2023 review by Zhao and colleagues confirmed the broader interaction framework: mushroom polysaccharides and gut microbiota interact bidirectionally, with systemic effects including neurological pathway modulation.^[10]

The Human Clinical Evidence: Lion's Mane and the 2023 RCT

Most gut-brain axis mushroom evidence is preclinical. The only double-blind randomized controlled trial is a 2023 pilot study by Docherty and colleagues testing lion's mane supplementation in healthy young adults.^[7]

The study tested both acute (single-dose) and chronic (ongoing supplementation) effects on cognitive function, stress, and mood. Both acute and chronic effects were measurable in the double-blind design. The researchers found lion's mane produced cognitive improvements and reduced stress markers.

Two things to note about what this study can and cannot establish. What it establishes: measurable human-level cognitive and mood effects are real and demonstrable in a controlled trial. What it cannot determine: whether those effects came from the gut-mediated pathway (polysaccharides feeding SCFA-producing bacteria, whose butyrate reaches the brain) or the direct pathway (hericenones and erinacines crossing the blood-brain barrier without the gut as intermediary).

The Cha 2024 review provides a partial answer. It found that lion's mane supplementation increases SCFA-producing bacteria, and the increase in those bacteria correlates with neuropeptide Y levels in the brain.^[1] Neuropeptide Y is associated with stress resilience and cognitive function. This points toward the gut-mediated pathway contributing to lion's mane's cognitive effects, alongside the direct NGF-stimulating pathway.

For the full gut-brain-cognitive evidence picture, the gut-brain axis and mushrooms: how your microbiome mediates cognitive benefits examines that specific angle in depth.

The 2025 Frame: Fungi as Candidate Natural Antidepressants

A 2025 review by Gong and colleagues took the broadest current view of where the evidence stands.^[11] Published in Nutrients, it explicitly framed edible and medicinal fungi as "candidate natural antidepressants," with gut microbiota modulation identified as a primary mechanism alongside direct neurochemical effects.

That framing is a step beyond prior reviews, which treated gut microbiota modulation as a secondary mechanism. Gong 2025 names it as central.

A 2023 review by Lazur and colleagues in Antioxidants provided a complementary picture, identifying five specific pathways through which medicinal mushrooms produce antidepressant-like effects: gut microbiota modulation, the tryptophan-kynurenine pathway (where inflammation diverts tryptophan away from serotonin synthesis), HPA axis modulation, neuroinflammation reduction, and BDNF upregulation.^[8] The gut microbiota pathway connects to several of the others: when microbiota are disrupted, butyrate production falls, neuroinflammation rises, BDNF production drops, and the tryptophan-kynurenine pathway skews toward inflammation. The gut effects and brain effects are downstream of the same initial shift.

Early evidence for the gut-mediated pathway in humans came from a 2013 in vitro study by Yu and colleagues, who tested Turkey tail (Trametes versicolor) extract against actual human fecal microbiota samples and showed it significantly altered their composition.^[9] This was early demonstration that mushroom polysaccharide effects on gut bacteria are not limited to rodent models; human gut bacteria respond to them too.

The current evidence base: the mechanism is well-characterized in animal models and increasingly supported in humans. The Docherty 2023 RCT provides human proof-of-concept for cognitive and mood effects. Human trials specifically measuring gut microbiota changes alongside brain outcomes would be needed to confirm that the gut-mediated pathway is the active one in people, rather than (or alongside) direct brain-active compounds. That trial has not been done.

For the mood and depression angle, the microbiome-mood connection: where mushrooms fit in focuses on that specific research. For neurotransmitter specifics, mushrooms, gut bacteria, and neurotransmitter production covers the serotonin, dopamine, and GABA evidence.

The Bottom Line

Mushroom polysaccharides feed gut bacteria that communicate with the brain through the vagus nerve, immune signaling, and neurotransmitter precursor production. A 2021 animal study traced Reishi's sleep effect to a gut microbiota-dependent serotonin pathway. A 2022 mouse study found ordinary Agaricus mushrooms at dietary levels prevented brain oxidative stress via SCFA-producing bacteria. A 2023 human pilot RCT found lion's mane produced measurable cognitive and mood improvements. A 2025 review named gut microbiota modulation as a primary antidepressant mechanism. Human trials isolating the gut-specific pathway remain the critical gap.

Frequently Asked Questions

What is the gut-brain axis?

The gut-brain axis is the bidirectional communication network between gut bacteria and the brain, operating through three channels: the vagus nerve (a direct physical connection from gut to brainstem), immune signaling (gut bacteria shifts trigger cytokine release that reaches the brain), and neurotransmitter precursor production (gut bacteria produce serotonin precursors and SCFA that cross into brain tissue). About 90% of the body's serotonin is produced in the gut through this system.

How does gut health affect your mental health?

Gut bacteria influence brain function through neurotransmitter production, inflammatory signaling, and direct neural communication via the vagus nerve. When beneficial gut bacteria are depleted (a state called dysbiosis), serotonin precursor production drops, pro-inflammatory cytokines rise, and BDNF production in the brain is reduced. These changes are associated with depression, anxiety, and cognitive impairment in both animal and human research.

What mushrooms are best for gut and brain health?

Lion's mane (Hericium erinaceus) is the best-studied for both gut and brain effects, with evidence from a 2023 double-blind human RCT showing cognitive and mood improvement. Reishi (Ganoderma lucidum) has the most direct mechanistic evidence for gut-mediated brain effects, with a 2021 study tracing its sleep promotion to a gut microbiota-dependent serotonin pathway. Agaricus bisporus (white button mushrooms) showed neuroprotective effects via SCFA-producing bacteria in a 2022 dietary study. All species work through the same gut prebiotic mechanism.

Can eating mushrooms improve your mood?

Animal evidence shows mushroom consumption modulates gut bacteria that affect serotonin production and brain oxidative stress. A 2023 double-blind human pilot RCT found lion's mane supplementation produced measurable mood improvements in young adults. A 2025 review framed edible fungi as candidate natural antidepressants based on gut microbiota mechanisms. The human clinical evidence is limited to one pilot RCT; larger trials would be needed to establish this as a clinical intervention.

Do functional mushrooms help with anxiety?

Functional mushrooms affect gut bacteria that modulate the HPA axis (the stress-response system) and GABA production, both of which are involved in anxiety. The Docherty 2023 RCT found lion's mane reduced stress markers in a double-blind trial. A 2023 review by Lazur and colleagues identified HPA axis modulation as one of five distinct pathways through which medicinal mushrooms produce antidepressant and anxiolytic effects. All the human evidence comes from one pilot study; the animal evidence for multiple species and pathways is stronger.

Sources & References

1. 1RTHM-00868·Cha, Sara et al. (2024). “A review of the effects of mushrooms on mood and neurocognitive health across the lifespan..” Neuroscience and biobehavioral reviews.Study breakdown →PubMed →↩
2. 2RTHM-00878·Jayachandran, Muthukumaran et al. (2017). “A Critical Review on Health Promoting Benefits of Edible Mushrooms through Gut Microbiota..” International journal of molecular sciences.Study breakdown →PubMed →↩
3. 3RTHM-01308·Yin, Chaomin et al. (2020). “The Impact of Mushroom Polysaccharides on Gut Microbiota and Its Beneficial Effects to Host: A Review..” Carbohydrate polymers.Study breakdown →PubMed →↩
4. 4RTHM-01242·Liu, Xiaoxiao et al. (2020). “A Review on Linking the Medicinal Functions of Mushroom Prebiotics with Gut Microbiota..” International journal of medicinal mushrooms.Study breakdown →PubMed →↩
5. 5RTHM-00731·Yao, Chunyan et al. (2021). “Ganoderma lucidum promotes sleep through a gut microbiota-dependent and serotonin-involved pathway in mice..” Scientific reports.Study breakdown →PubMed →↩
6. 6RTHM-01520·García-Sanmartín, Josune et al. (2022). “Agaricus Mushroom-Enriched Diets Modulate the Microbiota-Gut-Brain Axis and Reduce Brain Oxidative Stress in Mice..” Antioxidants (Basel.Study breakdown →PubMed →↩
7. 7RTHM-00821·Docherty, Sarah et al. (2023). “The Acute and Chronic Effects of Lion's Mane Mushroom Supplementation on Cognitive Function, Stress and Mood in Young Adults: A Double-Blind, Parallel Groups, Pilot Study..” Nutrients.Study breakdown →PubMed →↩
8. 8RTHM-00837·Lazur, Jan et al. (2023). “Discovering the Potential Mechanisms of Medicinal Mushrooms Antidepressant Activity: A Review..” Antioxidants (Basel.Study breakdown →PubMed →↩
9. 9RTHM-00573·Yu, Zhuo-Teng et al. (2013). “Trametes versicolor extract modifies human fecal microbiota composition in vitro..” Plant foods for human nutrition (Dordrecht.Study breakdown →PubMed →↩
10. 10RTHM-01835·Zhao, Jiahui et al. (2023). “The Interaction between Mushroom Polysaccharides and Gut Microbiota and Their Effect on Human Health: A Review..” Biology.Study breakdown →PubMed →↩
11. 11RTHM-02087·Gong, Pin et al. (2025). “Edible and Medicinal Fungi as Candidate Natural Antidepressants: Mechanisms and Nutritional Implications..” Molecular nutrition & food research.Study breakdown →PubMed →↩