SOURCE-LINKED STUDY SUMMARY
Urolithin A Muscle Trial: Endurance Signal, Mixed Results
PED EVIDENCE INTERPRETATION
Did urolithin A improve muscle performance?
In 66 older adults, urolithin A did not significantly outperform placebo on the primary walking-distance or ATP-production outcomes. A secondary endurance advantage appeared at two months, not four. [1]
- Design
- Double-blind randomized trial
- Population
- 66 adults aged 65–90; 33 per group
- Comparison
- Oral urolithin A 1,000 mg/day vs placebo
- Duration
- 4 months; endurance also tested at month 2
The evidence at a glance
| Outcome / timing | Urolithin A | Placebo | Uncertainty / meaning |
|---|---|---|---|
| 6-minute walk, month 4 [1] | +60.8 m | +42.5 m | Primary; no significant between-group difference |
| Hand ATP production, month 4 [1] | +0.07 mM/s | +0.06 mM/s | Primary; no significant between-group difference |
| Hand endurance, month 2 [1] | +95.3 contractions | +11.6 contractions | Secondary; significant at month 2, not month 4 |
OUR READING OF THE EVIDENCE
What this changes
The signal merits confirmation using a prespecified functional outcome and follow-up long enough to test persistence. [1][2]
What it does not establish
It does not establish better everyday mobility, muscle growth or longer life. A null comparison also does not establish equivalence. [1]
Put it in context
The related trial also had a null primary endpoint
A separate four-month trial in untrained adults aged 40–64 reported improvements in some strength measures, but not its primary endpoint, peak power output. Different tests and populations mean it is not a direct replication of the older-adult endurance finding. [2]
What would strengthen the case?
An independently conducted trial that replicates a meaningful functional improvement would be more persuasive than accumulating favorable biomarker changes. Biomarker movement alone does not tell a reader how much better they will move or feel.
Sources and transparency
Amazentis funded and participated in the older-adult trial. The small, predominantly female, all-White sample limits generalizability. Short follow-up cannot settle long-term safety. [1]
Questions this study helps answer
Did this trial show that urolithin A builds muscle?
No. It assessed mitochondrial and performance outcomes; the results do not establish hypertrophy. An endurance finding is different from increased muscle size. [1]
Why does the two-month versus four-month distinction matter?
A benefit observed at one assessment may not persist. The primary four-month comparisons and later endurance assessment should be considered alongside the favorable two-month result. [1]
Original compact summary and study details
- What was studied
- A blinded, randomized trial tested urolithin A against placebo for walking ability, muscle endurance and cellular energy production.
- Who / model studied
- 66 adults aged 65 to 90 took part in a 4-month trial.
- Studied dose & schedule
- In this randomized study of adults aged 65 to 90 years, participants received 1000 mg urolithin A orally each day or placebo for 4 months. This was the assigned study intervention; the abstract does not describe a starting-dose adjustment or any individualized regimen.
- What the study found
- Muscle endurance measures improved, but walking distance and the primary cellular-energy measure did not improve significantly versus placebo.
- Limitations & context
- This was a small study, predominantly in women, and all participants were White. The authors called for further confirmation.
Read summary source ↗ · Prepared 9/15/2026 · AI-assisted, source-based summary
Review record & corrections
Summary prepared: . Source scope: abstract. This is an AI-assisted source summary, not an independent clinician sign-off.
No public field-by-field revision history is available for this card yet. The date above is the summary date, not proof that every field was updated then.
Inspect the source · Correction policyResearch findings apply to the population and conditions studied. This educational summary is not a treatment recommendation or a formal assessment of study quality.
Original publication ↗ · DOI: 10.1001/jamanetworkopen.2021.44279