Urolithin A and Muscle Strength: What the Clinical Trials Show

Why muscle is Urolithin A's best-studied benefit

Search "urolithin a muscle strength" and you will find something unusual for a supplement ingredient: an actual stack of registered, randomized, placebo-controlled human trials. Skeletal muscle became the flagship research target for a simple reason. Muscle is one of the most mitochondria-dense tissues in the body, so if a compound genuinely improves mitochondrial quality, muscle is where you would expect to see it first and measure it most cleanly. Grip strength, leg torque, contractions-to-fatigue, and walking distance are all objective, repeatable endpoints.

The result is a body of evidence that moved from a first-in-human safety study to functional strength and endurance trials in less than a decade. Independent reviewers have started to weigh it up, and their verdict is more cautious than most marketing. A 2026 systematic review in Frontiers in Nutrition pooled five randomized controlled trials (236 participants) and described the overall effect on muscle outcomes as directionally favorable but statistically inconclusive, with low certainty. Some strength and endurance measures improved within individual trials, while others, including grip strength, VO2 peak and lean mass measured by DXA, did not. A 2025 systematic review posted as a preprint (not yet peer reviewed) went further and concluded that the evidence is not yet sufficient to say Urolithin A improves muscle function, calling for larger trials. That honesty matters: this is a promising supportive nutrient with early human data, not a proven performance aid.

The mitophagy mechanism in muscle

Urolithin A is a gut-microbiome metabolite. When you eat ellagitannins from pomegranate, walnuts, and berries, certain gut bacteria convert them into Urolithin A. The catch is that many people carry the wrong microbiome mix and produce little to none, which is the rationale for taking a standardized Urolithin A supplement that delivers a consistent, clinically studied dose directly.

Inside muscle cells, Urolithin A's headline action is stimulating mitophagy: the targeted recycling of damaged or aging mitochondria. As we age, worn-out mitochondria accumulate and the cell's ability to clear them declines, leaving a less efficient energy supply. By nudging mitophagy, Urolithin A helps muscle cells make room for healthier mitochondria and support more efficient energy production. The first-in-human study in Nature Metabolism (2019) confirmed the ingredient was safe and orally bioavailable, and showed it induced a gene-expression signature of improved mitochondrial and cellular health in skeletal muscle, along with favorable shifts in plasma acylcarnitines (a mitochondrial biomarker). A separate 2025 randomized, placebo-controlled trial in Nature Aging (HUMAN) looked at immune cells rather than muscle: four weeks of 1,000 mg per day in about 50 middle-aged adults was associated with more naive CD8+ T cells and signs of increased mitochondrial capacity in those cells. It did not measure strength, but it suggests the mitochondrial effects are not confined to one tissue.

What the key RCTs actually measured

Middle-aged adults (Cell Reports Medicine, 2022; HUMAN). In a four-month randomized trial in roughly 90 adults aged 40 to 64, participants took 500 mg or 1,000 mg of Urolithin A daily. The Cell Reports Medicine study reported leg muscle strength improvements of about 12%, driven by the hamstring (knee flexor) measurements, alongside favorable changes in blood biomarkers of mitochondrial health such as acylcarnitines and C-reactive protein. Not every endpoint separated from placebo: hand-grip strength, quadriceps strength and VO2 max did not change significantly, which the authors reported transparently.

Older adults (JAMA Network Open, 2022; HUMAN). In older adults (65-90), participants took 1,000 mg daily for four months. The JAMA Network Open trial did not beat placebo on its co-primary endpoints (six-minute walk distance and muscle fatigue at the two-month mark), an honest null result worth stating plainly. However, it did show significantly improved muscle endurance, measured as the number of contractions to fatigue in a hand muscle and a leg muscle, plus reductions in plasma acylcarnitines and C-reactive protein, signaling better mitochondrial efficiency and lower systemic inflammation markers.

Resistance-trained athletes (JISSN, 2024; HUMAN). Evidence is not limited to older or sedentary groups. An eight-week randomized, double-blind, placebo-controlled study in resistance-trained male athletes (500 mg/day) reported gains in some endurance and strength measures, such as bench-press repetitions to failure and quadriceps isometric strength, though one-rep max strength did not differ from placebo, with favorable effects on inflammation, oxidative stress, and protein-metabolism markers. A 2025 Frontiers review on Urolithin A in sports nutrition frames these as early but promising athletic applications.

Trials at a glance

Who the evidence applies to, and the doses used

The strongest, most consistent human data sit with middle-aged and older adults, the groups where natural mitophagy declines and where a strength or fatigue-resistance nudge is most noticeable. The athlete data extend the picture to younger, already-trained bodies, but that literature is smaller and newer. Across trials, the studied doses cluster at 500 mg and 1,000 mg per day, taken for roughly 8 to 16 weeks, so this is a daily-habit, play-the-long-game ingredient rather than a pre-workout you feel in an hour. For a study-by-study breakdown beyond muscle, see our summary of the urolithin A clinical studies, and for what the research means specifically for older adults, our page on strength and physical function in aging.

SOMA's formulation is built around the higher clinically studied dose. Our SOMA Urolithin A gummies deliver 1,000 mg of standardized Urolithin A per serving, matching the amount used in the four-month strength and endurance trials, in a format that is easy to keep taking daily.

Honest limits

Three things kept in view keep expectations grounded. First, effect sizes are modest and not every endpoint in every trial reached significance, as the older-adult study candidly showed. Second, Urolithin A is not a replacement for resistance training; the mechanism supports mitochondrial quality, but muscle still grows and gets stronger primarily through progressive loading, adequate protein, and sleep (our guide to protecting muscle after 50 covers practical training and protein targets). Think of it as backing your training, not standing in for it. Third, under DSHEA this is a structure/function ingredient that supports normal muscle function and strength in healthy people. It is not intended to diagnose, treat, cure, or prevent any disease, including age-related muscle loss as a medical condition. If you have a health concern or take medication, talk with your clinician first.

Frequently asked questions

Does Urolithin A build muscle on its own? No. The trials point to support for muscle strength and endurance and mitochondrial efficiency, not standalone muscle growth. It works best paired with resistance training and adequate protein, where it may help support your training capacity over time.

How long until effects show up? Human strength and endurance trials ran about 8 to 16 weeks, and biomarker changes appeared within weeks in the first-in-human study. Plan on consistent daily use across a couple of months rather than expecting an acute effect.

What dose was used in the studies? The randomized trials used 500 mg or 1,000 mg of standardized Urolithin A per day. The four-month strength and endurance studies in adults commonly used 1,000 mg daily, the dose SOMA's gummies provide.

Can't I just eat pomegranates and walnuts? You get the precursors (ellagitannins) from those foods, but converting them into Urolithin A depends on having the right gut bacteria, which many people lack. A standardized supplement delivers a consistent, clinically studied amount directly, bypassing that variability.

Is it only for older adults? The clearest evidence is in middle-aged and older adults, but a 2024 trial in resistance-trained athletes reported endurance and strength benefits too, so it is being studied across a range of ages and fitness levels.

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