Full profile
| Also known as | L-Ergothioneine |
|---|---|
| Best for | Memory and healthy aging, on early evidence only |
| Evidence grade | Emerging — mostly preclinical or preliminary human data |
| Studied dose range | 10–25 mg daily across the two small human cognition trials. |
| Time to effect | Studied over 16 weeks in adults with memory complaints and over a year in the mild-cognitive-impairment pilot; blood levels rose, but no durable cognitive effect is established. |
| Best form | Purified L-ergothioneine at a stated milligram dose. Mushroom powders provide it too, in variable and usually unstated amounts. |
| Food sources | Mushrooms (the richest dietary source) |
Evidence, honestly graded
Emerging. Most of the case is observational or preclinical: lower blood ergothioneine was associated with faster cognitive decline in older adults attending memory clinics (Wu 2022), and oral ergothioneine improved object-recognition memory in mice (Nakamichi 2021). The larger randomized trial (Zajac 2025; 147 adults aged 55–79 with subjective memory complaints; 10 or 25 mg/day for 16 weeks) raised blood ergothioneine but did not demonstrate a between-group benefit on its primary composite-memory outcome: the 25 mg group improved within-group at week 4 and did not sustain it. Reaction time showed a treatment-by-time interaction, but no pairwise between-group comparison reached significance, so the improvements differed by dose and time rather than cleanly favouring ergothioneine over placebo. Self-rated prospective memory and sleep onset improved dose-dependently, reaching significance at 25 mg. That trial was funded by Phyto Tech Corp (Blue California), which also employs one of its authors. A separate, publicly funded pilot in 19 people with mild cognitive impairment (Yau 2024, 25 mg/day for a year) reported better performance on a learning measure and steadier plasma neurofilament light. Two small trials, one without a between-group primary result and one at pilot scale in a clinical population, is Emerging territory.
See the full grading rubric — study type, replication, population match, and dose adequacy — in The Evidence Standard.
Side effects
- Well tolerated in the 16-week trial
- Long-term human safety data are limited
Who should avoid it or check first
- Pregnant or breastfeeding without clinician guidance
Interactions
- Limited interaction data — discuss with a clinician if on medication
What to look for on a label
- Look for a stated milligram dose of L-ergothioneine rather than a mushroom-extract weight.
- Treat "longevity vitamin" language as marketing — ergothioneine is not an established essential nutrient.
References
- Zajac IT, Kakoschke N, Kuhn-Sherlock B, May-Zhang LS (2025). Nutraceuticals, 5(3):15No between-group benefit on the primary composite-memory outcome; a within-group improvement at week 4 on 25 mg that was not sustained; a treatment-by-time interaction on reaction time with no significant pairwise between-group comparison; self-rated prospective memory and sleep onset improved at 25 mg.
- Yau 2024, Journal of Alzheimer's Disease — ergothioneine pilot in mild cognitive impairment. Double-blind, randomized, placebo-controlled pilot in 19 people aged 60+ with mild cognitive impairment; 25 mg/day for a year improved performance on a learning measure and steadied plasma neurofilament light versus placebo. Publicly funded (Singapore). PMID 39544014. A pilot in a clinical population — too small, and the wrong population, to carry a healthy-adult claim.
- Wu 2022, Antioxidants — plasma ergothioneine and cognitive decline (observational). In 470 older adults attending memory clinics in Singapore, lower plasma ergothioneine was associated with poorer baseline cognition and faster decline. An association, not evidence that supplementing helps. PMID 36139790.
- Nakamichi 2021, Current Molecular Pharmacology — oral ergothioneine in mice. Oral ergothioneine enhanced object-recognition memory in mice. Preclinical. PMID 32048982.
Grades and studied doses are our conservative reading of the human research, shown for education. They are not product claims, and a studied dose is not a recommended dose.
Revision history
Every change to this ingredient's evidence status, dated and explained. The full cross-library log lives at Evidence Updates.
- 2026-09-14New profile
New profile at Emerging. The larger randomized trial, funded by the ingredient's maker, showed no between-group benefit on its primary memory outcome, and the other is a 19-person pilot in mild cognitive impairment; the rest of the case is observational and animal research.
See how Ergothioneine compares on grade, dose, and goal in the Evidence Explorer.
