Urolithin A Research Library
Scientific papers can be difficult to interpret because headlines often highlight the most positive result. Our summaries include outcomes that did not improve, study design, population, duration and commercial relationships.
How to read our summaries
- Primary outcome: the main question a trial was designed to answer.
- Secondary outcome: an additional planned measurement. Useful, but usually less definitive.
- Exploratory outcome: a hypothesis-generating analysis that requires confirmation.
- Statistical significance: evidence that a result is unlikely to be explained by chance under the analysis assumptions. It does not show that the effect is large or important.
- Clinical significance: whether a change is likely to matter to health, symptoms, function or quality of life.
Study 1: First-in-human safety and mitochondrial biomarkers
Paper: Andreux PA et al. Nature Metabolism (2019).[2]
Design: randomised first-in-human studies involving single doses and four weeks of repeated dosing.
Population: healthy, sedentary older adults.
Intervention: several doses; repeated-dose findings highlighted at 500 mg and 1,000 mg daily.
Main findings: Urolithin A was absorbed at tested doses and had a favourable safety profile over the study period. Four weeks altered plasma acylcarnitines and mitochondrial gene expression in skeletal muscle.
What it did not establish: improvement in daily energy, strength, disability, disease risk or lifespan.
Key limitations: early-phase study, short duration, biomarker-focused and commercially connected authorship.
Our verdict: important proof of human exposure and biological activity; not a benefits trial.
Study 2: Pomegranate conversion and microbiome variability
Paper: Singh A et al. European Journal of Clinical Nutrition (2022; published online 2021).[3]
Design: randomised crossover comparison of pomegranate juice and a food product containing 500 mg Urolithin A.
Population: 100 healthy adults aged 18 to 80.
Main findings: 12% had detectable Urolithin A at baseline; around 40% became substantial converters 24 hours after pomegranate juice. Direct Urolithin A produced more consistent and greater circulating exposure.
What it did not establish: that supplementation improves health, or that the producer percentages apply to every population.
Key limitations: open-label, short pharmacokinetic comparison, commercial sponsorship and a threshold-based producer definition.
Our verdict: useful evidence that food-to-Urolithin conversion varies widely.
Study 3: Older adults, muscle endurance and mitochondrial health
Paper: Liu S et al. JAMA Network Open (2022).[4]
Design: randomised, double-blind, placebo-controlled trial.
Population: 66 adults aged 65 to 90.
Intervention: 1,000 mg Urolithin A daily or placebo for four months.
Primary outcomes: change in six-minute walk distance and maximal ATP production in hand skeletal muscle.
Primary result: no statistically significant improvement versus placebo.
Secondary findings: better performance in repeated-contraction endurance tests for hand and leg muscles and changes in plasma acylcarnitines, ceramides and C-reactive protein.
Safety: no statistical difference in adverse events between groups during the trial.
Key limitations: participants were relatively well functioning, a substantial placebo improvement affected the walking comparison, and the sample was modest.
Our verdict: mixed evidence — negative primary outcomes with positive secondary endurance and biomarker findings.
Study 4: Middle-aged adults, strength and exercise performance
Paper: Singh A et al. Cell Reports Medicine (2022).[5]
Design: randomised, double-blind, placebo-controlled study.
Population: 88 adults aged approximately 40 to 65 who were overweight and generally inactive.
Intervention: placebo, 500 mg or 1,000 mg Urolithin A daily for four months.
Main findings: improvements were reported in certain strength measures with Urolithin A; the higher dose affected some exercise-performance measures. Muscle analyses showed changes in proteins associated with mitophagy.
Key limitations: moderate sample size, multiple outcomes and strong commercial involvement. Several authors were employees, board members or advisers of the sponsor.
Our verdict: encouraging functional and mechanistic findings that require independent confirmation.
Study 5: Systematic review of human evidence
Paper: Kuerec AH et al. Ageing Research Reviews (2024).[6]
Scope: five human studies, 250 healthy participants, 10 to 1,000 mg daily, 28 days to four months.
Review findings: Urolithin A was associated with changes in inflammation-related markers, mitochondrial genes, autophagy markers and fatty-acid oxidation. It increased muscle strength and endurance in included studies but did not consistently affect anthropometrics, cardiovascular outcomes, physical function, maximal ATP production, mitochondrial biogenesis or dynamics.
Our verdict: a useful independent synthesis showing a signal in muscle and biomarkers, alongside substantial gaps and inconsistent outcomes.
Study 6: Resistance-trained male athletes
Paper: Zhao H et al. Journal of the International Society of Sports Nutrition (2024).[8]
Design: eight-week randomised, double-blind, placebo-controlled study.
Population: 20 resistance-trained male athletes.
Main findings: reported changes in selected muscle endurance, strength, inflammatory, oxidative-stress and protein-metabolism measures.
Key limitations: very small sample, male-only and specialised population; many outcomes increase the need for replication.
Our verdict: hypothesis-generating evidence for athletes, not sufficient for a general performance claim.
Study 7: Highly trained male distance runners
Paper: Whitfield J et al. Sports Medicine (2025).[9]
Design: randomised, controlled supplementation study lasting four weeks.
Population: highly trained male distance runners.
Main findings: recovery-related molecular and indirect muscle-damage markers improved, perceived exertion fell and aerobic capacity increased; running performance was not further enhanced.
Our verdict: possible recovery effects without demonstrated performance enhancement.
Study 8: Immune ageing trial
Paper: Denk D et al. Nature Aging (2025; corrected 2026).[7]
Design: randomised, double-blind, placebo-controlled trial.
Population: 50 healthy middle-aged adults.
Intervention: 1,000 mg daily or placebo for 28 days.
Main findings: changes in CD8+ T-cell phenotypes and fatty-acid oxidation, with additional immune-population, functional and exploratory transcriptomic findings.
What it did not establish: fewer infections, better vaccine response, lower disease incidence or a treatment effect.
Key limitations: small, short, biomarker-intensive and commercially connected.
Our verdict: credible early human mechanism research, not a consumer immunity claim.
Study 9: Topical skin research preprint
Paper: D’Amico D et al. medRxiv preprint (2023).[10]
Design: report combining mechanistic work and randomised topical studies using 0.5% or 1% Urolithin A-containing formulations.
Reported findings: changes in skin-ageing measures and UVB-induced redness.
Key limitations: preprint status, commercial authorship, formulation complexity and limited independent replication.
Our verdict: suitable for an “emerging research” article, not definitive cosmetic efficacy copy.
Research gaps
Priority questions include:
- Do benefits persist beyond four months?
- Which people are most likely to benefit?
- What is the smallest effective exposure?
- Are changes meaningful to quality of life and independence?
- How does supplementation compare with structured exercise?
- Are effects additive to resistance and aerobic training?
- What are the long-term safety and interaction profiles?
- Can independent research groups replicate the main findings?
- Do oral and topical finished products perform as claimed?