Human cells carry a transporter, OCTN1, whose main known job is to pull one specific molecule out of the bloodstream and concentrate it inside tissue. We cannot synthesise that molecule. Fungi can. Evolution rarely builds dedicated machinery for a nutrient that does nothing — and yet, after twenty years of that argument, the entire human trial record for ergothioneine is one pilot study with nineteen people in it.
Ergothioneine is a sulfur-containing amino acid derivative made by fungi and some bacteria, not by plants or animals. Humans absorb it through a dedicated transporter (OCTN1, gene SLC22A4) identified in 2005, retain it for weeks, and excrete less than 4% of an oral dose. Mushrooms are the richest dietary source, ranging from 0.15 to 7.27 mg per gram of dry weight depending on species. Whole-blood levels fall significantly after age 60 and are lower again in people with mild cognitive impairment. The one randomised human trial gave 25 mg three times a week for a year to 19 older adults with mild cognitive impairment: learning-test scores improved and a marker of neuronal damage stayed flat, while the placebo group's marker rose significantly. That is the whole clinical base.
It is an unusual position for a nutrient: strong biology, thin trials, and a supplement market already selling it as a longevity compound. Here is what is actually established.
What Is Ergothioneine?
It is a thiourea derivative of the amino acid histidine, abbreviated ET, and it exists in nature almost exclusively because fungi and certain soil bacteria make it. Plants do not synthesise it; they take it up from soil fungi. Animals do not synthesise it either — every molecule in your body arrived through your mouth.
Chemically it is stable in a way most antioxidants are not. Ergothioneine sits overwhelmingly in the thione form at physiological pH rather than the reactive thiol form, which means it does not auto-oxidise in the bloodstream the way cysteine or glutathione readily do. That stability is why it survives digestion, circulation and storage inside cells.
Why Does the Body Have a Transporter for It?
This is the core of the case, and it is a good one. In 2005 Gründemann and colleagues reported in PNAS that the orphan transporter OCTN1 — a protein whose physiological substrate had been unknown — turned out to be highly specific for ergothioneine, transporting it roughly a hundredfold more efficiently than the compounds it had previously been assumed to carry.
That reframed the molecule. A specific, high-affinity uptake system is expensive to maintain, and OCTN1 is expressed most strongly in tissues exposed to oxidative and inflammatory stress: bone marrow, erythrocytes, the lens of the eye, the liver, the intestinal lining.
Note carefully what this argument does and does not prove. It establishes that the body treats ergothioneine as worth collecting. It does not establish that eating more of it produces a measurable health outcome, and those are different claims.
How Much Is in Mushrooms?
Enough to matter, and it varies more than a tenfold range between species. Kalaras and colleagues at Penn State measured ergothioneine across mushroom species in 2017 and found levels from 0.15 to 7.27 mg per gram of dry weight — a roughly fiftyfold spread.
Three details from that work are worth carrying to the kitchen. Ergothioneine tracked closely with glutathione content across species (r = 0.62). It concentrated in the cap rather than the stem in the species tested. And Agaricus bisporus harvested in the third cropping flush contained more of both antioxidants than the first flush, which the authors read as a response to accumulated oxidative stress in the growing bed.
The practical implication is that no mushroom is a fixed dose of ergothioneine. Species, tissue and even growing cycle move the number, and no supplement label on the market discloses any of it.
What Happened in the One Human Trial?
Yau and colleagues in Singapore published it in 2024. Nineteen subjects aged 60 or over with mild cognitive impairment took either 25 mg of ergothioneine per capsule or placebo, three times a week, for one year, in a double-blind randomised design.
Two things came out of it. Subjects taking ergothioneine improved on the Rey Auditory Verbal Learning Test while the placebo group did not improve on any cognitive assessment. And plasma neurofilament light chain — a blood marker of ongoing neuronal damage — stayed stable in the ergothioneine arm while rising significantly in the placebo arm.
Read that second result the way the authors did: the headline is less that ergothioneine improved something and more that the untreated group deteriorated. It is the same shape as the long lion's mane Alzheimer's trial — deceleration rather than enhancement.
Nineteen people is a pilot. The authors called it one. A single pilot study is not a basis for a health claim, and anyone selling you ergothioneine as proven brain protection is running ahead of their own evidence.
Does Blood Level Predict Anything?
It correlates with things, which is not the same as predicting them. Cheah's 2016 analysis of an elderly Singaporean population found whole-blood ergothioneine declining significantly beyond age 60, and a subset with mild cognitive impairment had significantly lower plasma levels than age-matched controls.
The honest reading is that this could run in either direction. Low ergothioneine might predispose to neurodegeneration, as the authors proposed. Or declining health, appetite, diet quality and gut absorption might lower ergothioneine. A cross-sectional measurement cannot separate those.
The companion finding is often quoted as if it were about ergothioneine, and it is not. Feng's 2019 study of 663 Singaporeans aged 60 and over found that eating more than two portions of mushrooms per week was associated with reduced odds of mild cognitive impairment — odds ratio 0.43, 95% confidence interval 0.23 to 0.78 — independent of age, education, smoking, alcohol, hypertension, diabetes, heart disease, stroke and activity levels.
That is an association with eating mushrooms. Ergothioneine was not measured in those participants. Mushrooms also carry beta-glucans, B vitamins, vitamin D2, fibre and glutathione, and people who eat them twice a week differ from people who do not in ways no statistical adjustment fully captures.
Is It Safe?
On the available evidence, unusually so. Cheah's 2017 pharmacokinetic study gave pure ergothioneine orally to healthy volunteers and tracked it: absorption was avid, plasma and whole-blood concentrations rose substantially, and urinary excretion stayed below 4% of the dose. The body holds on to it.
Biomarkers of oxidative damage and inflammation — allantoin, 8-hydroxy-2'-deoxyguanosine, 8-iso-PGF2α, protein carbonylation, C-reactive protein — all trended downward, and the authors were explicit that most of those changes were non-significant. That is a properly reported null, and it is worth more than a press release.
In Yau's year-long trial, blood counts and kidney and liver function markers were unchanged throughout. Ergothioneine also has US FDA GRAS status as a food ingredient. Nothing here suggests a safety problem; it simply has not been tested in pregnancy, in children, or alongside medication, so the usual caution in our interactions guide applies.
Established, Suggested, Unproven
| Claim | Status | Evidence |
|---|---|---|
| Humans cannot synthesise it | Established | Basic biochemistry; dietary origin only |
| A dedicated transporter exists | Established | OCTN1 identified 2005, PNAS |
| Mushrooms are the main food source | Established | 0.15–7.27 mg/g dry weight across species |
| Retained rather than excreted | Established | Under 4% urinary excretion |
| Levels fall with age | Suggested | Cross-sectional, one population |
| Slows cognitive decline | Unproven | One pilot trial, n=19 |
| Extends lifespan | Unproven | No human data of any kind |
| Improves skin, energy, immunity | Unproven | No human trials on those endpoints |
Why "Longevity Vitamin" Is a Hypothesis, Not a Finding
The phrase comes from Bruce Ames, who proposed in 2018 that a class of nutrients — ergothioneine among them — are not needed for short-term survival but are needed for long-term health, and are therefore invisible to the classical deficiency-disease method that defined vitamins in the first place.
It is an elegant idea and it explains why ergothioneine would have escaped nutritional science for a century. It is also, by its own construction, difficult to test: proving that something prevents damage accumulating over forty years requires a forty-year trial nobody will fund.
So treat "longevity vitamin" as a research framework that earned a label, not as a demonstrated property. The same caution we apply to the wider category in our healthy aging ranking applies here.
What This Means for What You Buy
- Eat mushrooms as food if ergothioneine is the goal. The content figures come from whole mushrooms, and the cognitive association in Feng's study came from dietary portions, not capsules.
- Don't expect an extract to deliver it. Hot-water mushroom extracts are standardised on beta-glucans, and no label on the market states an ergothioneine figure — see what those label numbers actually mean.
- Favour caps over stems. Kalaras found both antioxidants concentrated in cap tissue in the species tested.
- Two portions a week is the dietary figure that has any human data behind it. It is not a dose; it is the threshold at which an association appeared in one cross-sectional study.
- Ignore ergothioneine claims on supplement marketing. If a product is sold on this molecule, ask for the measured content per serving. Nobody currently publishes one.
- Don't buy it for skin, energy or immunity. No human trial has measured those outcomes.
The Honest Summary
Ergothioneine has the most interesting mechanistic case in the whole mushroom-nutrient category and one of the weakest clinical ones. The transporter is real, the tissue distribution is real, the retention is real, the safety record is clean, and the trial evidence is a single pilot in nineteen people whose best result was that the placebo group got worse.
That combination justifies eating mushrooms regularly. It does not justify paying a premium for a molecule on a label, and it certainly does not justify the longevity claims already attached to it. If the funded trials arrive, this entry will need rewriting — which is more than can be said for most of the compounds sold beside it.
Frequently Asked Questions
What is ergothioneine and where does it come from?
It is a sulfur-containing derivative of histidine made by fungi and some soil bacteria. Humans and plants cannot synthesise it, so all of it in your body came from food — mostly mushrooms, and in smaller amounts from foods grown in fungal-rich soil.
Which mushrooms have the most ergothioneine?
Content ranges from 0.15 to 7.27 mg per gram of dry weight across species, a roughly fiftyfold spread, with cap tissue richer than stem tissue. Because growing conditions and harvest flush also move the figure, no species can be quoted as a fixed amount.
Is there any human trial evidence for ergothioneine?
One randomised pilot. Nineteen adults aged 60 and over with mild cognitive impairment took 25 mg three times weekly for a year; learning-test performance improved and a neuronal damage marker stayed flat, while it rose significantly in the placebo group.
Is ergothioneine safe to take?
Nothing in the published record suggests otherwise. A year of supplementation left blood counts and liver and kidney markers unchanged, and it holds GRAS status as a food ingredient. It has not been tested in pregnancy, in children, or with medications.
Should I buy an ergothioneine supplement?
There is no evidence-based dose to buy toward. The human data that exists concerns either 25 mg three times weekly in one small trial, or eating more than two portions of mushrooms per week — and dried culinary mushrooms are the cheaper route to the second.
Shop Ergothioneine-Rich Mushrooms
Ergothioneine comes from whole mushrooms, so this is a food purchase rather than a supplement one. Dried shiitake (50 g €39, 100 g €69) rehydrates into everyday cooking and is among the better-studied culinary species. Dried chanterelle (100 g €39, 500 g €139) and dried morels (100 g €39, 1 kg €299) cover the wild-harvested end. Browse the whole gourmet and forest mushroom range. Free shipping on orders over €50.
Related Articles
- Best Mushrooms for Healthy Aging
- Shiitake Mushroom for Health
- Morel Mushroom Nutritional Profile
- Chanterelle Mineral Content
- Beta-Glucan vs Polysaccharide on Labels
- Shiitake and Vitamin D2
- Lion's Mane and Longevity
Sources
- Gründemann D, Harlfinger S, Golz S, et al. Discovery of the ergothioneine transporter. Proc Natl Acad Sci U S A. 2005;102(14):5256-5261. PubMed 15795384
- Kalaras MD, Richie JP, Calcagnotto A, Beelman RB. Mushrooms: a rich source of the antioxidants ergothioneine and glutathione. Food Chem. 2017;233:429-433. PubMed 28530594
- Yau YF, Cheah IK, Mahendran R, et al. Investigating the efficacy of ergothioneine to delay cognitive decline in mild cognitively impaired subjects: a pilot study. J Alzheimers Dis. 2024;102(3):841-854. PubMed 39544014
- Cheah IK, Feng L, Tang RMY, Lim KHC, Halliwell B. Ergothioneine levels in an elderly population decrease with age and incidence of cognitive decline; a risk factor for neurodegeneration? Biochem Biophys Res Commun. 2016;478(1):162-167. PubMed 27444382
- Feng L, Cheah IK, Ng MM, et al. The association between mushroom consumption and mild cognitive impairment: a community-based cross-sectional study in Singapore. J Alzheimers Dis. 2019;68(1):197-203. PubMed 30775990
- Cheah IK, Tang RM, Yew TS, Lim KH, Halliwell B. Administration of pure ergothioneine to healthy human subjects: uptake, metabolism, and effects on biomarkers of oxidative damage and inflammation. Antioxid Redox Signal. 2017;26(5):193-206. PubMed 27488221
- Ames BN. Prolonging healthy aging: longevity vitamins and proteins. Proc Natl Acad Sci U S A. 2018;115(43):10836-10844. PubMed 30322941