Urolithin A vs Urolithin B Supplementation
Urolithin A supplementation is the only urolithin with established clinical evidence for human use, while urolithin B has no published human trials or safety data—making urolithin A the clear choice for supplementation. 1, 2
Evidence Base for Urolithin A
Urolithin A has been extensively studied in human clinical trials with demonstrated benefits:
Muscle endurance improvements: In older adults (65-90 years), urolithin A 1000 mg/day for 4 months significantly increased muscle endurance in both hand (FDI) and leg (TA) muscles at 2 months compared to placebo 1
Mitochondrial health biomarkers: UA supplementation upregulated mitochondrial genes, markers of autophagy, and fatty acid oxidation in healthy individuals across multiple studies 3
Anti-inflammatory effects: UA decreased plasma levels of acylcarnitines, ceramides, and C-reactive protein after 4 months of supplementation 1
Recovery benefits in athletes: In highly trained male distance runners, UA 1000 mg/day for 4 weeks reduced post-exercise muscle damage markers (creatine kinase), lowered ratings of perceived exertion, and showed a large within-group increase in VO2max (5.4%) 4
Safety profile: Across 250 healthy individuals in five studies, UA (10-1000 mg/day) for 28 days to 4 months showed only mild or moderate unrelated adverse events with favorable safety 3
Bioavailability and Dosing
Absorption advantage: Direct UA supplementation provides >6-fold higher plasma exposure compared to dietary precursors (pomegranate juice), overcoming gut microbiome variability 2
Microbiome independence: Only ~40% of people naturally convert ellagitannins to UA through gut bacteria, making direct supplementation necessary for consistent effects 2
Established dosing: Clinical trials consistently used 500-1000 mg/day with demonstrated efficacy and safety 1, 2, 3
Complete Absence of Urolithin B Evidence
No human clinical trials, safety data, or pharmacokinetic studies exist for urolithin B supplementation. The scientific literature contains only preclinical mechanistic studies of urolithin B, with zero evidence supporting its use in humans.
Clinical Recommendation Algorithm
For any adult considering urolithin supplementation:
- Choose urolithin A exclusively - it is the only form with human evidence 1, 2
- Dose at 500-1000 mg/day based on clinical trial protocols 1, 3
- Expect benefits after 2-4 months of consistent supplementation 1, 3
- Primary indications: Age-related muscle decline, exercise recovery, mitochondrial health optimization 4, 1
Critical Pitfalls to Avoid
Do not assume dietary sources are sufficient: Only 12% of people have detectable UA at baseline, and only 40% can convert dietary ellagitannins to UA 2
Do not use urolithin B: Complete absence of human data makes it inappropriate for supplementation regardless of theoretical mechanisms 5
Do not expect immediate performance gains: While UA improves recovery markers and muscle endurance, acute performance enhancement in elite athletes may be limited 4