Every cell in your body runs on tiny power plants called mitochondria. When they sputter, you feel it: fatigue sets in, muscles weaken, and recovery slows. Now, two recent studies have mapped, in molecular detail, how a sulfur-containing amino acid found in mushrooms, eggs, and certain meats physically enters those power plants and switches on an enzyme that keeps energy production humming.
The nutrient is ergothioneine, a compound humans cannot manufacture internally and must absorb from food. Scientists have known for years that the body hoards it, channeling it toward tissues under the most oxidative stress. What they did not know, until recently, was whether ergothioneine actually crosses into mitochondria or simply lingers in the fluid surrounding them. That question has now been answered.
Direct proof: ergothioneine gets inside mitochondria
Using mass spectrometry, researchers confirmed that ergothioneine is taken up directly into isolated mitochondria and accumulates inside the organelles of both treated cells and living animals, according to a study published in Biochemical and Biophysical Research Communications. That finding closes a longstanding gap. Earlier work had shown ergothioneine concentrating in stressed tissues, but no one had demonstrated it physically crossing the mitochondrial membrane. Proving accumulation inside the matrix, the organelle’s innermost compartment, gives scientists a mechanistic foothold for explaining how this nutrient influences cellular energy rather than acting as a generic antioxidant floating outside.
The enzyme it activates, and why that matters for exercise
A separate study, published in May 2026 in Cell Metabolism, goes further. That paper reports ergothioneine accumulates specifically in muscle mitochondria and directly activates an enzyme called MPST (mercaptopyruvate sulfurtransferase). Using proteome-wide thermal stability profiling, the team demonstrated that ergothioneine controls mitochondrial function and exercise performance through direct activation of MPST.
In practical terms, ergothioneine does not just park inside the organelle. It engages a defined molecular target that regulates how efficiently mitochondria produce ATP, the chemical fuel cells burn for energy. In animal models, activating MPST shifted sulfur metabolism in ways that improved endurance and preserved mitochondrial integrity under physical stress.
Ergothioneine enters cells through a dedicated transporter called SLC22A4 (also known as OCTN1) and shows stress-linked tissue accumulation, meaning the body routes it toward organs facing the greatest oxidative burden. Foundational work published in the Proceedings of the National Academy of Sciences classified ergothioneine as a physiologic cytoprotectant, a substance the body actively retains because of its protective role. The presence of a high-affinity transporter, combined with long-term tissue retention, has led some researchers to argue ergothioneine behaves more like a vitamin than a typical dietary amino acid, though it has not been officially classified as one.
It is not the only nutrient guarding mitochondria
Ergothioneine is not working alone. A peer-reviewed study in Nature Cell Biology found that leucine, an amino acid abundant in beef, poultry, and dairy, inhibits ubiquitin-dependent degradation of outer mitochondrial membrane proteins. By doing so, leucine stabilizes the mitochondrial protein import machinery, expands the mitochondrial proteome, and boosts metabolic respiration.
The two nutrients act through entirely different mechanisms. Leucine protects the structural gateway proteins on the outer membrane. Ergothioneine activates an enzyme deep inside the organelle. That distinction raises an intriguing possibility: if the two nutrients operate on separate control points, combining them in the diet could produce additive or even synergistic gains in mitochondrial respiration. No published trial has tested that idea in humans, but the logic is grounded in their non-overlapping mechanisms.
Adding further complexity, recent work published in June 2026 in Nature Metabolism revealed that MICU proteins facilitate calcium-dependent mitochondrial metabolon formation and regulate cellular energetics independently of the mitochondrial calcium uniporter. The authors note this paper may still be in early-access status given its 2026 publication date. That discovery rewrites part of the textbook model for how cells match energy supply to demand. Rather than relying on a simple on-off calcium valve, mitochondria appear to host dynamic enzyme assemblies whose formation depends on calcium and MICU proteins, potentially intersecting with nutrient-driven pathways like those influenced by ergothioneine and leucine.
Where the science still has gaps
No published study has measured ergothioneine levels inside human mitochondria after a controlled dietary intake of specific foods. The mass spectrometry evidence comes from isolated organelles and animal models. Whether the concentrations achieved in those experiments match what a person absorbs from a plate of scrambled eggs and sauteed mushrooms remains an open question. Cooking methods, gut absorption efficiency, and individual differences in transporter expression could all influence how much ergothioneine actually reaches muscle mitochondria in people.
The Cell Metabolism paper identifies MPST as ergothioneine’s direct target and links its activation to improved exercise performance, but the effect sizes come from animal and cell-based models. No clinical trial has quantified how much MPST activation changes ATP output in older adults or in people with mitochondrial dysfunction. Without such data, claims that ergothioneine-rich diets prevent fatigue, slow aging, or enhance athletic performance remain hypotheses rather than established facts.
Genetic variation adds another wrinkle. SLC22A4 expression differs across individuals, which could mean some people absorb and retain far more ergothioneine than others from the same meal. In theory, those with higher transporter activity might enjoy greater mitochondrial protection under stress, while those with lower activity might see minimal benefit. Dose-response and genotype-stratified studies in humans have not yet been completed.
The leucine findings face a similar translation gap. Showing that leucine stabilizes outer membrane proteins in cell culture does not guarantee the same magnitude of benefit at the whole-body level, especially because leucine metabolism is already well studied in the context of muscle protein synthesis. High leucine intake also interacts with insulin signaling and overall protein balance, complicating any attempt to optimize it solely for mitochondrial support.
On safety, ergothioneine appears well tolerated in experimental models, and its presence in common foods suggests low toxicity. But concentrated supplements could push plasma levels far beyond what traditional diets deliver. Without multi-year safety data, it is unclear whether chronically elevating mitochondrial sulfur metabolism through MPST activation carries trade-offs, such as altering redox-sensitive signaling or interacting with medications that affect oxidative stress.
What this means for your plate, not your supplement shelf
The strongest evidence here comes from direct physical measurements, not statistical associations or food-frequency questionnaires. Mass spectrometry confirmation of ergothioneine inside mitochondria is a hard data point. Thermal stability profiling that pinpointed MPST as a binding partner provides a specific biochemical mechanism, not a vague claim about antioxidant support. These methods reduce the confounding that plagues much of nutrition science.
But mechanistic clarity does not automatically translate into clinical benefit. Many compounds enhance mitochondrial function in isolated cells yet fail to improve symptoms, performance, or disease outcomes in people. The current ergothioneine literature sits squarely in this mechanistic phase: detailed, internally consistent, and increasingly sophisticated, but not yet validated in randomized human trials.
For now, the practical takeaway is straightforward but modest. Diets that include ergothioneine-rich foods, particularly mushrooms (the most concentrated dietary source), along with adequate high-quality protein supplying leucine, are broadly aligned with mitochondrial health as understood from current lab data. The evidence does not yet justify high-dose supplementation or sweeping claims about anti-aging benefits.
What these studies do provide is a sharper map of how specific nutrients reach specific targets inside the cell’s most critical organelle. As human trials begin reporting on mitochondrial endpoints, exercise capacity, and long-term safety, the mechanistic insights from these papers will either be confirmed as clinically meaningful or revised as one chapter in a more complex story of how diet shapes the energy your cells produce every second of every day.
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*This article was researched with the help of AI, with human editors creating the final content.
