The Nutrient Your Body Can’t Make but Refuses to Let Go: Why Scientists Call Ergothioneine a Candidate “Longevity Vitamin”

Chapter 1

A Door Built for One Guest

In 2005, a small pharmacology team at the University of Cologne set out to answer what looked like a routine question. A protein called OCTN1 sits in the outer membrane of many human cells, and for years textbooks had filed it as a general-purpose carrier for small, positively charged molecules. Nobody had checked what it actually preferred to carry.

So the team checked. They placed the human protein into cultured cells, offered it a wide range of candidate molecules and measured what went through.

The answer surprised everyone, including the researchers. The molecule OCTN1 moved most efficiently was not a drug, a hormone or a common nutrient. It was a sulphur-containing compound with an unwieldy name: ergothioneine. And it went through more than 100 times more efficiently than the molecules the transporter was supposed to be for.

That would be a curiosity if ergothioneine were something we make ourselves. We do not. The human body has no way to build it. Every molecule of ergothioneine in your blood and tissues arrived from food.

This chapter is about that puzzle. Why would evolution keep a dedicated transporter for something we cannot produce? And what happens to ergothioneine once it is inside?

Section 1

The Transporter Nobody Expected

The Cologne team, led by Dirk Gründemann, published their result in the Proceedings of the National Academy of Sciences. Their findings were clear enough that they proposed a new name for the protein: ETT, short for ergothioneine transporter.

Two details make the finding unusual. First, the selectivity: a closely related carrier from the same family did not move ergothioneine at all. Second, the efficiency: ergothioneine moved through OCTN1 more than a hundredfold more efficiently than the compounds it had been assumed to carry.

In biology, specialised equipment is expensive. Cells do not usually maintain a high-precision transporter for a molecule that does not matter. That is why many researchers read the 2005 study as a hint that ergothioneine has a job to do in the body, even if the exact job is still being worked out.

One transporter, one preferred passenger: OCTN1 moves ergothioneine far more efficiently than anything else tested.

Section 2

Made by Fungi, Wanted by Us

If we cannot make ergothioneine, who does? The answer is a short list of organisms: fungi and certain bacteria. Plants and animals pick it up second-hand.

For people, by far the richest source is mushrooms. A 2017 analysis from Penn State measured ergothioneine across many common and specialty species and found levels ranging from about 0.15 to 7.27 mg per gram of dried mushroom, nearly a fiftyfold spread between the lowest and the highest.

That spread matters. It means two people who both say “I eat mushrooms” can take in very different amounts, depending on which species they buy and how often. We will come back to the plate in Chapter 4.

For now, hold on to the strange shape of the story: a molecule made by fungi, carried into our cells by a door that seems built for it, in a body that cannot make a single molecule of its own.

Section 3

The Molecule We Hold On To

The next question is what happens after ergothioneine is absorbed. In 2017, researchers at the National University of Singapore ran one of the first studies to give pure ergothioneine to healthy volunteers. Participants took 5 mg or 25 mg a day for a week, and the team tracked blood and urine closely.

Two findings stood out. Blood levels rose clearly, and stayed up. And very little was lost: less than 4% of the dose appeared in the urine. Most water-soluble compounds are flushed out quickly. Ergothioneine was not.

A 2023 review by Barry Halliwell and colleagues, who have studied the molecule for years, summarised it this way: ergothioneine is taken up rapidly by a transporter largely or completely specific for it, and once taken up it is retained in the body for weeks or months.

That combination led the American biochemist Bruce Ames to make a bold suggestion in 2018. In a paper on nutrients needed for long-term health rather than immediate survival, he listed ergothioneine as a candidate “longevity vitamin”.

The word candidate is doing real work in that sentence. Ergothioneine is not an official vitamin, there is no recommended daily intake, and no deficiency disease has been defined. Ames was proposing a hypothesis to be tested, not announcing a conclusion. The rest of this article looks at how that hypothesis is holding up.

Chapter 2

What Population Studies See

In the early 1990s, about 30,000 people in the Swedish city of Malmö agreed to something remarkable. They filled in detailed food diaries, answered questionnaires about how they lived, and gave blood samples that were frozen and stored. Then researchers waited. For decades.

Long waits like this are how population science works. You measure many things in healthy people, follow them for years, and see which measurements travel with which outcomes.

In 2019, a team from Lund University went back to those frozen samples with a modern question: which molecules in the blood mark a genuinely healthy diet, and do any of them say something about the future?

Section 1

Twenty-One Years in Malmö

The researchers measured 112 metabolites in blood from 3,236 people who had no heart disease or diabetes when they gave their sample. They first asked which metabolites lined up with a health-conscious eating pattern. Ergothioneine came out on top: it was the metabolite most strongly connected to that pattern.

Then they followed the outcomes. Over a median of 21.4 years, 843 participants died, 603 developed cardiovascular disease and 362 developed diabetes.

For every one standard deviation higher ergothioneine at the start, the risk of coronary disease was about 15% lower, the risk of cardiovascular death about 21% lower and the risk of death from any cause about 14% lower, after adjusting for the usual risk factors.

The authors described ergothioneine as an independent marker of lower risk, one that might be shaped by what people eat. A marker is the right word. We will come to why in Section 3.

Population studies follow thousands of people for years. Higher ergothioneine has repeatedly travelled with better outcomes.

Section 2

Memory, Measured

Malmö looked at the heart and survival. Other teams have looked at the brain.

In the Japanese town of Hisayama, researchers measured serum ergothioneine in 1,344 residents aged 65 and over who did not have dementia, and followed them for a median of 11.2 years. During that time, 273 people developed dementia.

The pattern was graded: the higher a person’s ergothioneine, the lower their risk of later diagnosis. People in the highest quarter had roughly 45% lower risk than those in the lowest quarter. The link held after adjusting for a long list of cardiovascular, lifestyle and dietary factors, including how many vegetables people ate.

A 2026 study from the Rotterdam cohort in the Netherlands came at the question from a different angle. It examined 991 blood metabolites in 1,082 middle-aged adults without dementia and asked which ones lined up with cognitive test scores. Fourteen metabolites showed associations that were confirmed in independent groups. Ergothioneine showed the largest effect of them all.

Smaller studies point the same way. In Singapore, whole-blood ergothioneine was found to fall significantly beyond the age of 60, and people with mild memory problems had lower levels than their peers. In Japan, a detailed blood analysis of frail and non-frail older patients found ergothioneine among the molecules that were lower in frailty, although that study involved only 19 people.

Section 3

Cause or Consequence?

Here is where careful reading matters more than enthusiasm. Every study in this chapter is observational. It shows that higher ergothioneine and better outcomes appear together. It does not show that one causes the other.

There are at least two honest alternative explanations.

First, diet as a whole. Ergothioneine was the clearest blood marker of a health-conscious eating pattern in Malmö. People with high levels may simply eat better in many ways, and the other parts of that diet could explain some or all of the benefit.

Second, reverse causation. People who are becoming unwell often eat less varied food. Low ergothioneine could partly be a result of declining health rather than a cause of it.

Researchers try to account for these effects statistically, and the Hisayama link survived adjustment for vegetable intake. But statistics cannot fully remove them. That is why scientists call ergothioneine a candidate longevity vitamin, and why the next chapter goes into the laboratory, where cause and effect can be tested directly.

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Chapter 3

Inside the Lab

A population study can follow thousands of people for decades, but it can never hand half of them a molecule and the other half nothing, then wait for the end of their lives. In animals, researchers can. That is exactly what a team in Japan did with ergothioneine.

Laboratory studies cannot tell us what will happen in people. What they can do is test whether a molecule is capable of changing ageing at all, and how it might be doing it.

Section 1

The Mouse Lifespan Study

In 2024, researchers published a lifetime study in GeroScience. Male mice received ergothioneine in their drinking water, about 4 to 5 mg per kilogram of body weight a day, from 7 weeks of age until the end of their lives.

The supplemented mice lived longer: their median lifespan was about 16% longer than that of the control group. At 88 weeks, which is old age for a mouse, they also showed smaller age-related declines in body weight, fat mass and movement speed, and performed better on learning and memory tasks.

The team saw a similar pattern in tiny nematode worms, C. elegans, where ergothioneine extended both lifespan and the stretch of life spent free of frailty.

Before anyone gets carried away, three caveats belong right next to that result.

Laboratory work can test cause and effect, but its results still have to be confirmed in people.

Section 2

A Clue to Mechanism

If ergothioneine does something useful, how? For years the default answer was “it is an antioxidant”. A 2025 study in Cell Metabolism proposed something more specific.

Working in worms and in aged rats, the researchers found that ergothioneine improved markers of healthspan. In the old rats it improved exercise endurance, muscle mass and blood-vessel growth in muscle, alongside higher NAD+ levels in muscle.

They then traced a chain of events. Ergothioneine acted as an alternative fuel for an enzyme called CSE, boosting production of a small signalling gas, hydrogen sulphide. That gas chemically tags hundreds of proteins, and one of those tags switched on an enzyme called cGPDH, which accounted for most of the rise in NAD+. When the team blocked that pathway, ergothioneine’s effects disappeared.

If you read our article on walking speed and the sixth vital sign, the NAD+ part will sound familiar: ageing muscle tends to run low on it. It is intriguing to see an unrelated molecule converge on the same pathway, but these are animal results, and they need to be tested in people.

Section 3

What Didn’t Work

A fair picture includes the studies that did not go the way supporters of ergothioneine might hope. Here are four.

A genetic study pointing the other way. Mendelian randomisation uses natural genetic variation to approximate a randomised trial. A 2024 analysis of 1,400 blood metabolites found that genetically predicted higher ergothioneine was linked with a higher risk of Alzheimer’s disease. That is the opposite of the Hisayama pattern, and it is a useful reminder that the story is not settled.

No difference by brain amyloid. In the Australian KARVIAH cohort, cognitively normal adults aged 65 to 90 were grouped by the amount of amyloid in their brains. Plasma ergothioneine did not differ between the groups.

A mushroom trial with a null result. In a 2026 Dutch trial, adults aged 60 and over took 5 g a day of a white button mushroom powder or a placebo around their annual flu vaccination. Blood ergothioneine rose in the mushroom group, confirming people took it, but there was no significant effect on the vaccine response or on illness during the season.

The antioxidant question. Ergothioneine is a strong antioxidant in the test tube. But Halliwell’s 2023 review notes that evidence for antioxidant activity being its main job inside the body is weak, just as it is for vitamin C and the flavonoids. The real function may lie elsewhere.

Chapter 4

Food First, Then Fill the Gap

Picture a week of ordinary European meals: porridge, a sandwich, pasta with tomato sauce, a chicken salad, fish on Friday. Nutritious enough. Yet it may contain very little ergothioneine, because the one food that supplies most of it never appeared.

That is the practical heart of this article. Your body appears to want ergothioneine and keeps what it gets. How much it gets depends almost entirely on your plate.

Section 1

How Much Is on Your Plate

Mushrooms are the main source by a wide margin. The 2017 Penn State analysis found a range of 0.15 to 7.27 mg per gram of dried mushroom. Because fresh mushrooms are mostly water, that translates very roughly to a few milligrams up to several tens of milligrams in a 100 g portion, depending heavily on the species.

The same study found ergothioneine was more concentrated in the caps than in the stems, and that levels varied even within one species depending on how it was grown.

Several things follow from this:

Mushrooms are the richest food source of ergothioneine, and the amount varies widely by species.

Section 2

What Supplements Reliably Do

Here the human evidence is clear on one point. Ergothioneine supplements raise blood levels, and they do it within weeks.

In the 2017 Singapore study, 5 or 25 mg a day for a week raised blood levels, with less than 4% lost in urine. A 2025 Japanese study gave 5 or 10 mg a day for eight weeks. With 5 mg, average plasma ergothioneine rose from about 3.4 to 5.5 µmol/L; with 10 mg, from about 3.5 to 8.0 µmol/L. In the same paper, a separate 16-week placebo-controlled trial at 8 mg a day reported better subjective sleep quality, an early and self-reported finding that needs confirming.

Longer use has also been studied. In a Singapore pilot trial, 19 adults aged 60 and over with mild memory problems took 25 mg three times a week, or a placebo, for a full year. Safety markers for blood, kidney and liver stayed normal. The ergothioneine group did better on one learning test and had steadier levels of a blood marker of nerve-cell stress than the placebo group.

With only 19 people, that is a pilot: a reason to run larger trials, not a conclusion. The same is true of most human ergothioneine research so far. What is established is that the molecule is absorbed, retained and well tolerated in these studies. Whether raising levels changes long-term health in people is still under study.

Section 3

The Honest Bottom Line

Pull the four chapters together and a consistent picture emerges.

Your body cannot make ergothioneine but has a dedicated transporter to absorb it and holds on to it for weeks. Levels fall with age. In large population studies, higher levels travel with lower cardiovascular risk, lower mortality and better brain health, though diet quality and illness may explain part of that. In animals, ergothioneine extended healthspan and pointed to a plausible mechanism. In people, supplements reliably raise levels, and the first trials of benefit are small.

That is exactly the kind of evidence that justifies the word candidate in “candidate longevity vitamin”, and exactly the kind that makes a sensible, low-risk plan worth having.

If you choose a supplement, ours is ERGO-SUPREME: 10 mg of bio-fermented L-ergothioneine per capsule, combined with 250 mg of ferulic acid, so one capsule a day sits at the lower end of that range and two at the upper end. You will find it in the reader reward below, for anyone who passes the Final Master Quiz.

Complete Reference List

Uptake, retention and food sources

Population studies

Human trials

Studies pointing the other way

Animal research