Key takeaways
- Ergothioneine is a sulphur-containing compound derived from histidine.
- It is made by fungi and some bacteria; humans obtain it from food.
- Mushrooms, especially Oyster types, are among the richest dietary sources.
- The body has a specific transporter for it, which has driven research interest.
- Human research is at an early stage; no health claims are authorised.
Ergothioneine is one of the more unusual compounds found in mushrooms, and one of the few for which mushrooms are among the richest dietary sources. This article explains what it is, where it comes from, how the body handles it, what research in people has and hasn’t shown, and why scientists find it so intriguing.
A short history
Ergothioneine was first isolated in 1909 by the French pharmacist Charles Tanret, from ergot, a fungus that grows on rye. That is where the “ergo” in its name comes from. Interest came and went for most of the twentieth century, because nobody could explain why the body contained it. That changed in 2005, when a German research team discovered a transporter protein that the human body uses specifically to take up ergothioneine. Publications on ergothioneine have grown rapidly since.
What is ergothioneine?
Ergothioneine is a sulphur-containing compound derived from the amino acid histidine. Unlike many sulphur compounds, it is unusually stable, because of the way its sulphur atom is held in the molecule. It is water-soluble and heat-stable.
Who makes it?
Ergothioneine is produced by fungi and by certain bacteria, including some soil bacteria and cyanobacteria. Plants and animals, including humans, don’t make it. Plants take it up from fungi and bacteria in the soil, and animals obtain it from food, which is why levels in plant foods can vary with the soil they were grown in.
A dedicated transporter
In 2005, researchers at the University of Cologne, led by Dirk Gründemann, showed that a transporter protein called OCTN1, encoded by the gene SLC22A4, carries ergothioneine far more efficiently than any other substance tested, more than a hundred times more efficiently than the compounds it had previously been thought to carry. They proposed renaming it the ergothioneine transporter, ETT.
Later animal studies found that without this transporter, ergothioneine is absent from cells and tissues. The existence of a specific, efficient transporter for a compound we can’t make ourselves is one of the main reasons scientists think ergothioneine may have a physiological role, though what that role is has not yet been established.
How the body handles it
In a 2017 study in Singapore, healthy volunteers were given pure ergothioneine at 5 mg or 25 mg a day. It was rapidly absorbed and largely retained, with levels in the blood rising substantially and less than 4% appearing in the urine. This avid uptake and retention is consistent with the transporter findings.
Dietary sources
Mushrooms are the richest known dietary source. A 2017 Penn State study measuring 13 mushroom species found ergothioneine levels varied almost fifty-fold between species. Porcini had by far the highest levels, and common white button and portobello mushrooms were lower, though still higher than most other foods. Oyster and King Oyster mushrooms and shiitake are also often reported as good sources. The study also found ergothioneine was more concentrated in the cap than the stem. Smaller amounts occur in foods such as oats, beans and organ meats. See Oyster Mushroom Compounds Explained.
Stability and extraction
Ergothioneine is water-soluble and relatively stable to heat, so it survives cooking and is drawn out by hot water extraction. See Hot-Water Mushroom Extraction Explained.
What does research in people show?
Observational studies
The best-known human study is observational. Researchers in Sweden measured 112 compounds in the blood of 3,236 adults in the Malmö Diet and Cancer study, who were free of heart disease and diabetes at the start, and followed them for a median of 21 years. Ergothioneine was the compound most closely linked to a health-conscious eating pattern, and higher blood levels were associated with lower rates of coronary disease and death over the follow-up period.
This is an association, not proof of cause and effect. Because ergothioneine tracked a healthy diet so closely, it may simply be a marker of eating well, rather than something that itself makes a difference. Only controlled trials can separate the two.
Controlled trials
Controlled trials of ergothioneine are few and small, and most use purified ergothioneine rather than mushrooms. For example, a 2024 pilot study in Singapore gave 19 older adults with mild cognitive impairment 25 mg of ergothioneine or placebo three times a week for a year. It reported no changes in safety markers such as kidney and liver function, and some differences on cognitive and blood measures, but with so few participants, the researchers described it as a pilot to inform larger trials.
A proposed “vitamin”?
Some researchers have suggested ergothioneine might one day be regarded as a kind of vitamin, because we absorb and retain it so avidly yet can’t make it. This is an interesting scientific idea, not an established fact, and ergothioneine is not recognised as an essential nutrient.
Regulation
Synthetic ergothioneine has been assessed for safety as a novel food ingredient in Europe. No health claims are authorised for ergothioneine in the UK.
What we can reasonably conclude
Ergothioneine is a genuinely distinctive part of mushroom chemistry, with a fascinating biology: a dedicated transporter, avid absorption and long retention. Observational research links higher blood levels with better long-term outcomes, but that may reflect healthy diets generally. Controlled trials in people are small and early, and what ergothioneine does in the body is still being researched.
What remains uncertain
- What role ergothioneine plays in the body, if any.
- Whether higher intake causes any benefit, or simply marks a healthy diet.
- What amounts might be relevant, and whether mushroom-derived and synthetic ergothioneine behave the same way.
In summary
Ergothioneine is one of the reasons mushrooms are nutritionally interesting foods, and one of the most intriguing compounds in food science. What it does in people is still an open question. For more on mushroom chemistry, see Understanding Mushroom Science.
References
- Tanret C. Sur une base nouvelle retirée du seigle ergoté, l’ergothionéine. Comptes Rendus de l’Académie des Sciences. 1909;149:222–224.
- Gründemann D, et al. Discovery of the ergothioneine transporter. Proceedings of the National Academy of Sciences USA. 2005;102(14):5256–5261.
- 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. Antioxidants & Redox Signaling. 2017;26:193–206.
- Kalaras MD, Richie JP, Calcagnotto A, Beelman RB. Mushrooms: a rich source of the antioxidants ergothioneine and glutathione. Food Chemistry. 2017;233:429–433.
- Smith E, et al. Ergothioneine is associated with reduced mortality and decreased risk of cardiovascular disease. Heart. 2020;106(9):691–697.
- Yau YF, et al. Investigating the efficacy of ergothioneine to delay cognitive decline in mild cognitively impaired subjects: a pilot study. Journal of Alzheimer’s Disease. 2024. doi:10.1177/13872877241291253.
Study titles are reproduced as published and are not claims made by Spore & Bloom.
