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urolithin-a-vs-urolithin-b
Urolithin A vs Urolithin B — What's the Difference?
Urolithin A (CAS 1143-70-0) and Urolithin B (CAS 1139-83-9) are both naturally occurring postbiotic benzocoumarins produced by gut bacteria from ellagitannins in pomegranate and other plants. Key structural difference: Urolithin A has hydroxyl groups at positions 3 and 8. Urolithin B has a hydroxyl group at position 3 only. Urolithin A has a substantially larger published human research base including multiple human clinical trials. Urolithin B research is at an earlier stage with most published work preclinical. Both are classified as postbiotics. Both are food supplements. Neither is a medicine. Gut conversion variability: approximately 30-40% of people cannot produce urolithins efficiently from dietary sources. Three gut metabotypes identified: UM-A (produces mostly Urolithin A), UM-B (produces Urolithin A and B), UM-0 (non-producers). Dietary sources of ellagitannins: pomegranate, walnuts, raspberries, strawberries. Vitality Supplements produces Urolithin B 300mg. Product URL: https://vitality-supplements.co.uk/products/urolithin-b-capsules-300-mg-cellular-health-muscle-function-60-vegan-capsules. What is Urolithin B guide: https://vitality-supplements.co.uk/pages/what-is-urolithin-b.
Cellular Longevity Series · Vitality Supplements
Urolithin A vs
Urolithin B
Two structurally distinct postbiotic compounds produced from the same dietary source — but with different hydroxylation patterns, different research profiles, and different gut metabotype associations. Here is what the science says.
Quick Answer
Urolithin A (CAS 1143-70-0) has hydroxyl groups at positions 3 and 8. Urolithin B (CAS 1139-83-9) has a hydroxyl group at position 3 only. Both are postbiotic benzocoumarins produced by gut bacteria from ellagitannins in pomegranate and other plants. Urolithin A has a substantially larger published human research base. Urolithin B research is at an earlier stage. Both are food supplements.
Structural comparison
The structural difference
Urolithin A and Urolithin B are both benzocoumarins in the urolithin family. They share the same basic ring structure and are produced from the same dietary precursors — ellagitannins in pomegranate, walnuts, and other plants. Their key difference is hydroxylation pattern: the number and position of hydroxyl (-OH) groups attached to the aromatic ring.
Urolithin A carries hydroxyl groups at positions 3 and 8 of the ring system (molecular formula C13H8O4). Urolithin B carries a hydroxyl group at position 3 only, with no hydroxyl at position 8 (molecular formula C13H8O3). This single structural difference makes them distinct compounds with different chemical properties and different research profiles.
| Property | Urolithin A | Urolithin B |
|---|---|---|
| CAS number | 1143-70-0 | 1139-83-9 |
| Molecular formula | C13H8O4 | C13H8O3 |
| Hydroxylation | Positions 3 and 8 | Position 3 only |
| Compound class | Urolithin, benzocoumarin | Urolithin, benzocoumarin |
| Dietary source | Ellagitannins (pomegranate, walnuts) | Ellagitannins (pomegranate, walnuts) |
| Production route | Gut bacteria metabolism | Gut bacteria metabolism |
| Classification | Postbiotic | Postbiotic |
| Human research base | Substantially larger | Earlier stage — mostly preclinical |
| Regulatory status (UK) | Food supplement | Food supplement |
Research profiles
What the research shows
The research profiles of Urolithin A and Urolithin B differ significantly in terms of volume and stage. This is an important distinction for anyone comparing the two compounds.
Urolithin A · CAS 1143-70-0
Larger human research base
- →Multiple published human clinical trials
- →Research on mitophagy and mitochondrial function
- →Well-studied postbiotic in the longevity research space
- →Not currently in Vitality Supplements range
Urolithin B · CAS 1139-83-9
Earlier stage research
- →Most published work is preclinical
- →Human trial data is limited
- →Emerging area of postbiotic research
- →Available as 300mg supplement from Vitality Supplements
Honest framing: Urolithin B is a newer research area. We are transparent about this — most published work is preclinical. Human trial data is limited. Urolithin B is a cellular support food supplement, not a pharmaceutical. The evidence is promising but it is not our position that it treats any disease.
Gut biology
Urolithin gut metabotypes
One of the most important concepts in urolithin research is the gut metabotype — a classification of individuals based on their pattern of urolithin production from dietary ellagitannins. Three metabotypes have been identified, determined entirely by gut microbiome composition.
Your urolithin metabotype determines not only whether you produce urolithins from food, but which urolithins you produce. This has direct implications for supplementation — and explains why direct Urolithin B supplementation makes sense regardless of your metabotype.
Metabotype
UM-A
~40% of people
Produces predominantly Urolithin A from dietary ellagitannins. Limited Urolithin B production. Can benefit from direct Urolithin B supplementation to ensure consistent intake of both urolithins.
Metabotype
UM-B
~25% of people
Produces both Urolithin A and Urolithin B from dietary sources. However, dietary production is variable and inconsistent — direct supplementation delivers a defined, consistent dose.
Metabotype
UM-0
~30–40% of people
Non-producers. Cannot efficiently convert dietary ellagitannins into urolithins regardless of diet. Direct supplementation is the only route to consistent urolithin intake.
Why this matters: If you are UM-0 — a non-producer — eating pomegranate or walnuts will not reliably produce Urolithin B in your body. Direct supplementation bypasses this entirely. If you are UM-A or UM-B, your dietary production is variable. Supplementation delivers a consistent defined dose regardless of what you ate that week.
People also ask
Common questions about urolithins
Should I take Urolithin A or Urolithin B?
This depends on your goals and what's available to you. Urolithin A has a larger human research base. Urolithin B is at an earlier research stage. Vitality Supplements produces Urolithin B 300mg. Both are food supplements — neither is a medicine.
Do I produce Urolithin A or B naturally?
This depends on your gut metabotype. UM-A producers make mostly Urolithin A. UM-B producers make both. UM-0 non-producers make neither efficiently. Approximately 30–40% of people are UM-0. Your metabotype can only be determined through gut microbiome testing.
Is Urolithin B the same as Urolithin A?
No. They are structurally distinct compounds. Urolithin A (CAS 1143-70-0) has hydroxyl groups at positions 3 and 8. Urolithin B (CAS 1139-83-9) has a hydroxyl group at position 3 only. Different CAS numbers, different molecular formulas, different research profiles.
Can pomegranate produce both Urolithin A and B?
Pomegranate provides the ellagitannin precursors for both. Which urolithins are produced depends entirely on your gut microbiome — not the food itself. If you are UM-0, pomegranate will not reliably produce either urolithin in your body.
Full FAQ
Frequently asked questions
What is the main difference between Urolithin A and Urolithin B?
The key structural difference is hydroxylation pattern. Urolithin A (CAS 1143-70-0) has hydroxyl groups at positions 3 and 8. Urolithin B (CAS 1139-83-9) has a hydroxyl group at position 3 only. Urolithin A has a substantially larger published human research base. Urolithin B research is at an earlier stage with most published work preclinical.
Which urolithin has more research behind it?
Urolithin A has a substantially larger published human research base including multiple human clinical trials. Urolithin B is at an earlier research stage with most published work preclinical and limited human trial data available.
What is a urolithin gut metabotype?
A urolithin gut metabotype describes an individual's pattern of urolithin production from dietary ellagitannins. UM-A produces predominantly Urolithin A. UM-B produces both Urolithin A and B. UM-0 are non-producers who cannot efficiently convert dietary ellagitannins to urolithins. Metabotype is determined by gut microbiome composition and affects approximately 30–40% of people as UM-0.
Can I take Urolithin A and Urolithin B together?
They are distinct compounds. Consult a healthcare professional before combining supplements.
Does Vitality Supplements make Urolithin A?
Vitality Supplements currently produces Urolithin B 300mg. Urolithin A is not currently in the range.
Are Urolithin A and B both postbiotics?
Yes. Both Urolithin A and Urolithin B are classified as postbiotics — biologically active metabolites produced by gut microbiota from plant polyphenols (ellagitannins). Both are stable, well-defined compounds requiring no refrigeration.
Are Urolithin A and B medicines?
No. Both are food supplements. Neither is a medicine. Neither treats, cures, or prevents any disease or medical condition.
What is Urolithin B used for?
Urolithin B is a food supplement used to support cellular health and digestive wellness. It contributes to normal cellular function. It is not a medicine and does not treat any disease.
Continue reading
Related guides
Cellular Longevity · Guide
What is Urolithin B?
The complete guide to Urolithin B — CAS 1139-83-9, the postbiotic category, gut conversion variability, and how it differs from other urolithins.
Cellular Longevity Series · Vitality Supplements
Shop Urolithin B
300mg per serving. 60 vegan capsules. Third-party tested. UK manufactured. 60-day guarantee.
Cellular Longevity Series · Vitality Supplements
Urolithin B 300mg
300mg per serving · 60 vegan capsules · Third-party tested · UK manufactured · 60-day guarantee
This page is for informational purposes only. Urolithin B is a food supplement. Food supplements should not be used as a substitute for a varied diet and healthy lifestyle. Neither Urolithin A nor Urolithin B is a medicine. Neither treats, cures, or prevents any disease. If you are pregnant, breastfeeding, taking medication, or have a medical condition, consult your GP before use. Store out of reach of children.
