Ergothioneine

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1. What Ergothioneine Is

Ergothioneine is a thiohistidine derivative synthesised by certain fungi, bacteria, and actinomycetes. It does not occur naturally in the human body but is obtained through the diet—primarily from mushrooms such as Agaricus bisporus, as well as from cereals, meat, and fish. The compound accumulates in tissues with high oxidative stress, including the liver, kidneys, bone marrow, and the eye lens. Its chemical structure enables a stable thiol-disulphide interaction, distinguishing it from other antioxidants like glutathione. Ergothioneine is transported into cells via the specific transporter OCTN1 (organic cation transporter novel 1), which significantly influences its bioavailability and tissue distribution.

Uptake and measurement of ergothioneine are central to interpreting all studies. Since humans do not produce the compound endogenously, plasma concentration depends directly on dietary intake. Bioavailability varies by source: while ergothioneine from mushrooms is well absorbed, uptake from plant sources such as cereals is lower. The half-life in plasma is approximately 30 days, indicating slow excretion. Measurement is typically performed via HPLC-MS/MS (high-performance liquid chromatography with tandem mass spectrometry), with intracellular concentrations often exceeding those in plasma. These characteristics complicate the comparability of studies, particularly when different dosages or routes of administration are investigated.

2. What the Studies Show in Detail

The key human studies and most important reviews—by application, including population, duration, preparation, measured outcomes, and results as reported in the original publications. Numbers are included only where the study specifies them.

Distribution of controlled human trials by application—numbers are not additive, as a single study may be assigned to multiple categories:

Inflammation

The controlled pilot study by Weigand-Heller et al. (2012) investigated the bioavailability of ergothioneine from Agaricus bisporus mushrooms and its acute effects on antioxidant capacity and inflammatory markers in 10 healthy men. Measurement of erythrocyte ergothioneine concentration showed significant cellular uptake. Among inflammatory markers, a trend towards a blunted postprandial triglyceride response was observed, while antioxidant capacity (ORAC(total)) decreased after both dosages. C-reactive protein (CRP) showed no significant changes. The study showed the bioavailability of ergothioneine from mushrooms but provides no clear evidence of an anti-inflammatory effect under acute conditions. Limitations include the small sample size and short observation period of a few hours 1.

The planned ErgMS pilot project (2021) is designed as a randomised, double-blind, placebo-controlled trial with three arms (placebo, 5 mg/day, or 30 mg/day ergothioneine over 12 weeks) to assess the feasibility of a larger intervention study in individuals with metabolic syndrome. Primary endpoints include metabolic syndrome risk factors, while secondary endpoints cover oxidative stress (lipid peroxidation), inflammatory markers, platelet function, and liver enzymes. Additionally, the serum metabolome will be analysed. The study is not yet completed, so no results are available. The planned 12-week duration may provide initial insights into chronic effects if the dosages are adequate. A critical limitation is the lack of a dose-response relationship from prior studies to justify the selected dosages 2.

The OYSCOG study (2026) investigated the effects of a 12-week intervention with Pleurotus ostreatus mushrooms (four portions per week, ergothioneine content not explicitly stated) on cognition, mood, and inflammatory markers in 80 healthy older adults (aged 60–80). Compared to the placebo group, the mushroom group showed improvements in delayed word recognition and recall (RAVLT), as well as reductions in anxiety (DASS-21) and negative mood parameters (PANAS-X). In a preclinical model using rodent microglial cells, inflammatory markers cyclooxygenase-2 (COX-2) and NADPH oxidase 2 decreased, indicating potential anti-inflammatory effects in vitro. However, systemic inflammatory markers in humans were not measured in this study, and the relevance of these in vitro findings to human physiology remains to be investigated. The study suggests potential benefits, though the contribution of other mushroom compounds cannot be ruled out.

The acute OYSACO study (2026) examined the effects of Pleurotus mushrooms (0.5, 1, or 2 portions in a noodle soup) on cognition, mood, and inflammatory markers in 33 healthy older adults using a crossover design. Postprandial inflammatory markers nitrite, NADPH oxidase 2, and inducible nitric oxide synthase (iNOS) were significantly lower after mushroom consumption compared to placebo. Mood (Positive Affect) deteriorated over the course of the day only in the placebo group, not following the mushroom intervention. Cognitive effects were inconsistent. The study showed acute effects on inflammatory markers in blood samples, though the clinical relevance of these surrogate parameters remains to be investigated. The short observation period (6 hours) and small sample size limit the conclusiveness of potential implications 4.

Hypothesis The observed trends in reducing inflammatory markers (COX-2, NADPH oxidase 2, iNOS) in in vitro and acute preclinical studies suggest that ergothioneine or mushroom extracts may play a modulating role in inflammation in these models. However, whether these effects translate to long-term anti-inflammatory action in humans remains uninvestigated. The discrepancy between acute and chronic effects (e.g., ORAC decline vs. potential anti-inflammatory effects) remains an open question.

Oxidative Stress

The study by Nakamichi et al. (2025) used a physiologically based pharmacokinetic (PBPK) model to determine the effective dose of ergothioneine for influencing subjective sleep quality. In Study 1, participants received 5 or 10 mg/day of ergothioneine over 8 weeks, with plasma and blood concentrations measured. The optimised PBPK model showed that 8 mg/day over 16 weeks achieves an effective plasma concentration. In Study 2 (randomised, double-blind, placebo-controlled), administration of 8 mg/day over 16 weeks led to a significant improvement in subjective sleep quality (p < 0.05). This is the first study to propose a dose-finding strategy based on PBPK models, though objective sleep parameters or biomarkers for oxidative stress were not assessed 3.

The observational study by Yamazaki et al. (2021) compared metabolites in whole blood from dementia patients with those in healthy older adults using LC-MS. Ergothioneine was among the 26 metabolites significantly reduced in dementia (Group B: compounds with trimethylammonium structures, enriched in erythrocytes). The study shows that ergothioneine levels are reduced in dementia; whether this also holds for mild cognitive impairment and frailty was not examined. However, the design does not allow for causal inferences, and the contribution of other metabolites (e.g., glutathione, NADP+) remains unclear. The findings underscore ergothioneine’s potential as a marker for oxidative stress in the context of neurodegenerative diseases 9.

The study by Servillo et al. (2015) investigated the redox behaviour of ergothioneine (ESH) in human neutrophils and cell-free systems. Upon activation of neutrophils with phorbol-12-myristate-13-acetate (PMA), the desulfurisation product hercynine (EH) and, unexpectedly, the sulfonated form ergothioneine sulfonate (ESO₃H)—previously undescribed—were formed. Similar oxidation products emerged from the reaction of ESH with hypochlorite, hydrogen peroxide, or peroxynitrite. The study demonstrates that ergothioneine forms specific metabolites under oxidative stress, which may exert cytoprotective effects. However, data on the biological activity of ESO₃H or its relevance in vivo are lacking 10.

Hypothesis The consistent observation that ergothioneine is reduced under oxidative stress (e.g., dementia) suggests it may function as an endogenous protective mechanism. The formation of specific oxidation products such as ESO₃H could represent an underappreciated mechanism of cytoprotection. However, it remains to be demonstrated whether these metabolites themselves exert antioxidant effects or merely serve as markers of oxidative stress.

Gut and Microbiome

The study by Cheah et al. (2026) investigated whether ergothioneine is a significant source of trimethylamine-N-oxide (TMAO), a metabolite with a proven association with cardiometabolic and neurodegenerative diseases. Bioinformatic analyses revealed that the enzyme ergothionase—responsible for converting ergothioneine to trimethylamine (TMA)—is restricted to a few bacterial genera and is significantly less common than choline trimethylamine-lyase (TMA formation from choline). In a randomised, placebo-controlled human study, supplementation with 25 mg/day of ergothioneine over 7 days led to a significant increase in plasma ergothioneine concentrations without raising TMAO levels. In a cohort of heart failure patients, ergothioneine did not correlate with TMA or TMAO, whereas TMAO was clearly associated with TMA. The study provides no evidence that ergothioneine is a relevant source of TMAO and found no rise in TMAO in the context of microbial metabolism 5.

Hypothesis The findings suggest that, despite its structural similarity to choline or carnitine, ergothioneine is not metabolised via the TMA/TMAO pathway. This is relevant because TMAO is associated with cardiovascular risks, whereas ergothioneine exhibits protective effects. The study addresses an important safety concern, though it remains unclear whether long-term ergothioneine supplementation influences microbiome composition.

Oncology

The observational study by Olsen et al. (2020) identified metabolites in the plasma of 3,236 participants from the Malmö Diet and Cancer Study that were associated with a health-conscious dietary pattern (HCFP). Five metabolites, including ergothioneine, were significantly linked to the HCFP (p < 0.0004). Plausible: The study showed an inverse relationship between ergothioneine and cardiovascular events but provides no direct evidence regarding oncological endpoints. The association may be mediated by antioxidant or anti-inflammatory effects, though the design does not permit causal inferences (Olsen et al., 2020). What remains to be clarified is whether ergothioneine directly contributes to the observed health benefits or merely reflects other dietary or lifestyle factors.

Hypothesis The inverse association between ergothioneine and mortality or cardiovascular diseases may indicate its role as an antioxidant and cytoprotective agent. Whether ergothioneine also exerts protective effects in oncology remains an open question, as the study did not examine specific cancer endpoints.

Overall Picture

Across multiple studies, ergothioneine consistently demonstrates evidence of bioavailability and antioxidant effects in preclinical and observational settings. Its absorption from dietary sources (e.g., mushrooms) is well-documented, and its accumulation in erythrocytes suggests targeted distribution within the body. Observational studies link higher ergothioneine levels to reduced risks of cardiovascular disease, mortality, and cognitive decline; however, causal evidence from interventional studies with clinically relevant endpoints is still lacking. Anti-inflammatory effects are primarily observed in in vitro models or as changes in inflammatory markers in acute human studies, while long-term data on chronic use in humans are still pending.

Evidence for a direct oncological or microbiome-modulating effect remains insufficiently investigated. While ergothioneine does not contribute to the formation of TMAO—a risk factor for cardiovascular disease—it remains unclear whether it influences microbiome composition in the long term. The role of ergothioneine as an antioxidant has been shown in multiple studies, though these often do not isolate its effects from other dietary components (e.g., mushroom compounds) or determine the optimal dosage for specific applications.

3. How Robust Is the Research?

Research on ergothioneine spans a substantial number of studies, including basic research, observational studies, and controlled trials. The applications in controlled studies focus on metabolism, inflammation, fatigue, cognition, and antioxidant effects. The most frequently cited works are review articles and mechanistic studies that highlight the plausible therapeutic potential of the compound. The six controlled human trials are predominantly pilot studies with small sample sizes, concentrating on bioavailability, inflammatory markers, and cognitive parameters.

The methodological robustness of the evidence base is limited. The few controlled human studies are small, heterogeneous, and often not blinded. The most cited study (2012) examines bioavailability from mushrooms and acute effects on antioxidant capacity and inflammatory markers but provides no long-term data. More recent studies (2025/2026) showed effects on sleep quality, cognitive parameters, and metabolic parameters in pilot designs, but these have not yet been cited and thus lack independent replication. Observational studies show associations between ergothioneine plasma levels and ageing processes or neurodegenerative diseases but cannot establish causality. Basic research provides robust data on cellular uptake and antioxidant mechanisms, yet the translation into clinical application remains outstanding.

4. Common Claims — and What the Data Show

5. Profile: Molecule and Charge

Ergothioneine is not a single molecule but a mixture — there is no molecular formula and no fixed molecular mass. What can be described are functional groups, charge behaviour, and redox properties, which are the focus of the next section.

6. Charge, Electrons, Radicals

Ergothioneine exhibits electrochemical properties as a radical scavenger and chelator. In laboratory studies, regulation of the Nrf2 signalling pathway, which controls antioxidant defence mechanisms, has been demonstrated 11 22. Direct measurements of electron transfer or cation exchange capacity in humans are not available.

No electrochemical parameters such as charge state or redox potential of ergothioneine have been directly determined in humans to date. The described effects are based on cell and tissue studies. These include the reduction of mitochondrial ROS (mROS) 20 21, stabilisation of the mitochondrial membrane potential (ΔΨm) 20 21, and inhibition of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) 22. Animal or tissue models show activation of antioxidant enzymes such as superoxide dismutase (SOD). Whether these effects result from direct electron transfer or indirect signal modulation remains to be investigated.

7. Interactions with Other Substances

Substances from this platform that have been jointly investigated or discussed with ergothioneine in human studies and review articles — whether in combination, comparison, or shared mechanism of action. The number indicates studies in which both appear.

Data on interactions between ergothioneine and pharmaceuticals or nutrients are limited. In cell cultures, synergistic effects with other antioxidants have been observed, such as when combined with neuronal induction media or glutathione-like compounds, suggesting an enhancement of antioxidant capacity 28. A study in human cells indicates that ergothioneine acts intracellularly and does not interact through direct binding to external substances like 7-ketocholesterol (7KC) 23. The biosynthesis of ergothioneine occurs via enzymatic reactions, including a PLP-dependent C-S-lyase (EgtE), which transfers sulphur from cysteine to histidine 25 27. Whether these enzymes (e.g., CYP enzymes) are influenced by ergothioneine is not described. The absorption of ergothioneine from foods such as mushrooms (Agaricus bisporus) has been examined in controlled human studies, confirming its bioavailability 1.

Combinations of ergothioneine with other active compounds have been evaluated in preclinical models. In cell cultures and animal studies, enhanced protective effects against UVB-induced skin damage were observed when used in conjunction with Guang Chenpi extract or polydeoxyribonucleotide (PDRN) 26. Another study suggests potential synergistic effects with physical activity, such as promoting cognitive resilience in ageing, though without mechanistic clarification 24. Interactions with the microbiome or the oxidation of trimethylamine (TMA) to TMAO have been discussed in review articles, albeit without direct reference to ergothioneine. Whether ergothioneine influences the pharmacokinetics of other substances (e.g., through enzyme induction or inhibition) remains to be investigated. Data on binding affinities or interactions with specific medications are lacking.

8. Overdose, Tolerability, and Limitations

Data on the toxicity and upper limits of ergothioneine are available from subchronic toxicity studies. A No Observed Adverse Effect Level (NOAEL) of 800 mg/kg body weight per day was determined 29. Safety assessments using the Margin of Exposure (MOE) consistently showed values above the threshold of 300, with fewer than 0.3% of the general population and 1.3% of children aged 3 to 6 years falling below this level 29. Natural dietary exposure in China was classified as safe, with no indications of risk 29. Review articles reported no safety concerns with supplementation of up to 25 mg/day 30. Animal studies (zebrafish) demonstrated low toxicity at concentrations of ≤0.63 mg/mL.

No adverse effects or contraindications have been documented in the available studies. Ergothioneine exhibited protective effects against doxorubicin-induced cardiotoxicity in mouse models without promoting tumour growth or impairing chemotherapy efficacy 19 19. Observations in humans suggest a potential role in neuroinflammatory processes, with no toxic effects reported 12. Long-term data, interactions with medications, and dose-dependent effects in various populations remain to be examined.

9. The Most Robust Studies

Ranked by evidential strength, not by prominence. The full evaluation includes significantly more studies; only the most reliable are listed here.

Controlled Human Studies

• 1 The bioavailability of ergothioneine from mushrooms (Agaricus bisporus) and the acute effects on antioxidant capacity and biomarkers of inflammation (2012)
• 2 Ergothioneine supplementation in people with metabolic syndrome (ErgMS): protocol for a randomised, double-blind, placebo-controlled pilot study (2021)
• 3 Estimation and Validation of an Effective Ergothioneine Dose for Improved Sleep Quality Using Physiologically Based Pharmacokinetic Model (2025)
• A randomised controlled study to investigate the cognitive, mood, metabolic and anti-inflammatory effects of chronic oyster mushroom intervention in healthy adults (2026)
• 4 A randomised controlled study to investigate the cognitive, mood, metabolic and anti-inflammatory effects of acute oyster mushroom intervention in healthy adults (2026)
• 5 Is Ergothioneine an Important Source of Plasma Trimethylamine N-Oxide in Humans? (2026)

Observational Human Studies

• 6 The biology of ergothioneine, an antioxidant nutraceutical (2020)
• 7 Administration of Pure Ergothioneine to Healthy Human Subjects: Uptake, Metabolism, and Effects on Biomarkers of Oxidative Damage and Inflammation (2017)
• 8 Ergothioneine is associated with reduced mortality and decreased risk of cardiovascular disease (2020)
• 9 Whole-blood metabolomics of dementia patients reveal classes of disease-linked metabolites (2021)
• 10 An uncommon redox behaviour sheds light on the cellular antioxidant properties of ergothioneine (2015)
• 11 Ergothioneine: an underrecognised dietary micronutrient required for healthy ageing? (2023)
• 12 Effect of Ergothioneine on 7-Ketocholesterol-Induced Endothelial Injury (2021)
• 13 Could Ergothioneine Aid in the Treatment of Coronavirus Patients? (2020)
• Plasma protein thiols: an early marker of oxidative stress in asthma and chronic obstructive pulmonary disease (2016)
• 14 Low Plasma Ergothioneine Predicts Cognitive and Functional Decline in an Elderly Cohort Attending Memory Clinics (2022)
• 15 Ergothioneine and its prospects as an anti-ageing compound (2022)
• 16 Clinical and biochemical correlates of serum L-ergothioneine concentrations in community-dwelling middle-aged and older adults (2014)
• Reflections of an ageing free radical (2020)
• Repeated double cross-validation applied to the PCA-LDA classification of SERS spectra: a case study with serum samples from hepatocellular carcinoma (2021)
• Trimethylamine N-Oxide (TMAO) Impairs Purinergic-Induced Intracellular Calcium Increase and Nitric Oxide Release in Endothelial Cells (2022)
• 17 Multiomics analysis to explore blood metabolite biomarkers in an Alzheimer’s Disease Neuroimaging Initiative cohort (2024)
• 18 Mushroom intake and cognitive performance among US older adults: the National Health and Nutrition Examination Survey, 2011–2014 (2022)
• 19 Protection against Doxorubicin-Induced Cardiotoxicity by Ergothioneine (2023)

10. Summary

Ergothioneine is a well-documented antioxidant with established bioavailability from dietary sources, particularly mushrooms. Its uptake via the specific transporter OCTN1 and accumulation in tissues under high oxidative stress are shown in studies. Observational studies show associations between higher ergothioneine levels and markers linked to reduced risk for cardiovascular disease, mortality, and cognitive decline, though causality is not established. Acute human studies suggest inflammation-modulating effects, such as reductions in markers like NADPH oxidase 2 or iNOS. Safety in the context of microbial metabolism has been shown in studies, as ergothioneine does not contribute to the formation of the risk metabolite TMAO.

Hypothesis The consistent evidence of antioxidant and inflammation-modulating effects suggests that ergothioneine may play a protective role in the prevention of oxidative stress and neurodegenerative diseases. The observed improvements in cognitive parameters and sleep quality could indicate a neuroprotective effect. However, it remains unclear whether these effects are directly attributable to ergothioneine or mediated by synergistic interactions with other mushroom constituents. The formation of specific oxidation products, such as ergothioneine sulphonate (ESO₃H), may represent an underappreciated mechanism of cytoprotection, though its biological relevance has yet to be clarified.

To confirm the clinical relevance of ergothioneine, controlled long-term studies with clinical endpoints are required. These should determine the optimal dosage for specific applications such as inflammation, cognition, or oxidative stress, and compare the effects of isolated ergothioneine versus mushroom extracts. Additionally, population-specific data should be collected, for example, in patients with pre-existing conditions such as metabolic syndrome or neurodegenerative diseases. Clarifying the dose-response relationship and isolating the effects of ergothioneine from other dietary components remain key open questions.

11. Open Questions

• Long-term effects: Whether ergothioneine exerts clinically relevant effects on metabolism, inflammation, or cognition over months or years remains unresolved. Blinded long-term studies with hard endpoints are needed.
• Dosage and bioavailability: The optimal intake amount and source (dietary vs. supplement) are unclear. Studies with standardised dosages and comparable routes of administration are lacking.
• Clinical endpoints: Whether ergothioneine influences disease progression (e.g., neurodegeneration, cardiovascular disease) has never been systematically investigated. Interventional studies with clinically relevant parameters would be necessary here.

12. Further Paths

Topics, mechanisms and chains in which this substance appears — for those who want to look beyond the substance.

• Interaction network