Ergothioneine is a naturally occurring antioxidant amino acid that the human body cannot make on its own. Mushrooms are the richest known dietary source of it. Researchers are studying whether ergothioneine helps protect cells from oxidative stress, a process linked to aging and some chronic diseases, but human research on this topic is still early.
This guide explains what ergothioneine is, which mushrooms contain the most of it, what the science says so far, and how eating mushrooms differs from taking a concentrated supplement.
How Ergothioneine Works in the Body
Ergothioneine is a sulfur-containing compound made from the amino acid histidine. Only certain fungi and a few types of bacteria can produce it. Plants and animals, including humans, cannot make it themselves. Instead, plants absorb small amounts from soil fungi, and people get it almost entirely from food, with mushrooms supplying far more than any other common food.
Once eaten, ergothioneine is absorbed and carried into cells by a specific transport protein called OCTN1. This transporter concentrates ergothioneine in tissues that face high oxidative stress, such as the liver, kidneys, eyes, and bone marrow. This selective transporter system, along with the compound’s role in cell protection during stress, led some researchers to propose classifying ergothioneine as a “vitamin” in 2010. That classification is not official and remains debated, since ergothioneine has no confirmed deficiency disease and no established daily requirement.
In laboratory studies, ergothioneine appears to neutralize reactive oxygen and nitrogen species, unstable molecules that can damage DNA, proteins, and fats, and it also binds certain metal ions in ways that may limit oxidative damage. These are cell-level and biochemical findings, not evidence of a specific health outcome in people.
Which Mushrooms Have the Most Ergothioneine
Ergothioneine content varies widely by mushroom species. Penn State food scientists testing 13 mushroom species found that porcini, a wild variety popular in Italian foraging, contained by far the highest amount of any mushroom tested.
Among mushrooms found in typical grocery stores, the differences are smaller but still measurable:
- Highest tested overall: Porcini (wild-harvested), shown in Penn State research to contain far more ergothioneine than any cultivated variety tested.
- Higher among common grocery mushrooms: Shiitake, oyster, king oyster, and maitake (hen of the woods) can supply up to about 13 milligrams of ergothioneine in a standard 3-ounce serving.
- Moderate: Portabella and crimini mushrooms carry slightly more ergothioneine than white button mushrooms, though the difference is modest.
- Lower, but still meaningful: A standard 3-ounce serving of white button, crimini, or portabella mushrooms supplies up to about 5 milligrams of ergothioneine.
For comparison, the same researchers found that white button mushrooms, the most commonly eaten mushroom in the U.S., contain roughly 12 times more ergothioneine than wheat germ and about 4 times more than chicken liver, the two foods previously considered top sources.
Cooking does not appear to reduce ergothioneine levels in mushrooms, based on this research. A separate metabolomics comparison of white button, crimini, portabella, lion’s mane, maitake, oyster, and shiitake mushrooms confirmed that ergothioneine levels differ meaningfully by species, even among mushrooms that look similar on a grocery shelf.
What the Human Evidence Shows on Oxidative Stress and Aging
Most of what researchers know about ergothioneine’s effects on aging and disease comes from cell and animal studies, not controlled human trials. It’s important to separate what has actually been tested in people from what remains a laboratory hypothesis.
Human evidence
One human study measured blood ergothioneine levels in 439 adults ages 55 to 85 and found that levels were not affected by sex or the presence of chronic medical conditions, but were modestly lower in older participants within the group. This is an observational, correlational finding. It shows an association between age and blood levels, not proof that low ergothioneine causes aging-related decline, or that raising levels through diet changes outcomes.
A small pilot study at Pennsylvania State University tested whether ergothioneine from mushroom powder is absorbed by the body. Researchers gave healthy men mushroom-derived ergothioneine and measured blood levels afterward, confirming the compound is bioavailable from food. That study measured absorption and short-term blood markers, not long-term health outcomes.
Preclinical and mechanistic evidence
A review of ergothioneine’s biology notes it can cross the blood-brain barrier and has been reported to have beneficial effects on brain tissue in laboratory and animal research, alongside proposed antiaging, vascular, and neuroprotective roles. These effects have been studied mainly in cell cultures and animal models. Reviewers of this research are explicit that clear, well-defined clinical prevention or intervention trials of ergothioneine in chronic disease are still lacking.
A separate research group has proposed that ergothioneine could be considered a “longevity vitamin” based on the accumulating preclinical evidence, while also calling for further research into how factors like farming practices affect how much of it ends up in the food supply. That framing reflects a research hypothesis under active investigation, not an established medical conclusion.
Bottom line: Laboratory and animal research consistently shows antioxidant activity and proposes protective roles against aging-related cellular damage. Confirmed, large-scale human clinical trials linking mushroom ergothioneine intake to specific disease prevention or reversal do not yet exist.
Food Sources vs. Supplement Forms
Eating mushrooms as food is not the same as taking a concentrated ergothioneine supplement, and the research so far mostly reflects the food form.
- Whole mushrooms: The studies above measured ergothioneine intake from mushroom powder or standard food servings, delivering it alongside other nutrients and fiber, at doses similar to normal eating patterns.
- Isolated supplements: Concentrated ergothioneine supplements can deliver amounts well above what a typical diet provides. Human safety and effectiveness data at these higher, isolated doses are more limited than the food-based research described here.
- Species matters: Because ergothioneine content varies several-fold between mushroom species, a serving of one type of mushroom is not nutritionally interchangeable with another for this compound.
Evidence Limits and Who Should Use Extra Caution
Research on ergothioneine has real limits worth knowing before drawing conclusions:
- Most disease-prevention and anti-aging claims come from cell and animal research, not confirmed human trials.
- Human studies to date are small, short-term, or observational, meaning they can show associations but not prove cause and effect.
- No governing body has set an official daily requirement or upper safety limit for ergothioneine, so “how much is enough” is not a settled question.
- Ergothioneine content varies by mushroom species, growing conditions, and preparation, so intake estimates are approximate, not precise.
People who should talk with a qualified clinician before changing their diet or trying a supplement include those who are pregnant or breastfeeding, people managing a chronic health condition, anyone taking prescription medications, and people with known mushroom allergies. This article does not recommend starting, stopping, or changing any medication or supplement.
Frequently Asked Questions
Is ergothioneine a vitamin?
Not officially. Some researchers have proposed calling it a “vitamin” because the body cannot make it and relies on a dedicated transporter to absorb it, but no health authority has classified it as an essential nutrient with a set daily requirement.
Which mushroom has the most ergothioneine?
Penn State research testing 13 species found that porcini mushrooms had by far the highest ergothioneine content of any mushroom tested. Among common grocery store mushrooms, shiitake, oyster, king oyster, and maitake tend to contain more than white button, crimini, or portabella.
Does cooking destroy ergothioneine in mushrooms?
According to Penn State’s research, ergothioneine levels do not appear to decrease when mushrooms are cooked.
Can ergothioneine prevent aging or disease?
That has not been established in humans. Laboratory and animal research suggests protective, antioxidant-related mechanisms, and some researchers hypothesize a role in healthy aging, but controlled human trials confirming disease prevention or reversal are still lacking.
Educational Disclaimer
This article is for general educational purposes only and is not medical advice. It does not diagnose any condition, recommend a supplement, or suggest starting, stopping, or changing any medicine. Evidence on ergothioneine differs by mushroom species, preparation, and study type, and most findings described here come from laboratory, animal, or small early-stage human research rather than large clinical trials. Ask a qualified clinician about your personal risks, medicines, pregnancy, or symptoms. See our evidence grading and source policy for how we classify human versus preclinical research, our medical disclaimer for the full safety scope of this site, and our editorial team and review process for how articles like this one are checked before publication.