Urolithin A vs SS-31

Both aim to improve mitochondrial function but at different stages: urolithin A promotes mitophagy, SS-31 stabilises cardiolipin and respiratory function in existing mitochondria.

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Urolithin A

A gut-microbiome metabolite of ellagitannins (pomegranate, berries, nuts) that stimulates mitophagy — the recycling of damaged mitochondria.

BEST STUDIED FOR

Mitochondrial & longevity

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SS-31

A mitochondria-targeted tetrapeptide that binds cardiolipin in the inner mitochondrial membrane — approved in the US in 2025 for Barth syndrome.

BEST STUDIED FOR

Mitochondrial & longevity

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SIDE BY SIDE

	Urolithin A	SS-31
The key difference	Promotes removal of damaged mitochondria	Protects mitochondrial membranes
Class	Mitochondrial & longevity	Mitochondrial & longevity
Mechanism	Only some people’s gut bacteria convert dietary ellagitannins to urolithin A.	SS-31 concentrates in the inner mitochondrial membrane and binds cardiolipin, the lipid that holds the electron-transport chain together.
Status	Several randomised human trials in middle-aged and older adults and athletes; marketed as a supplement.	Accelerated US approval (September 2025) to improve muscle strength in Barth syndrome; further trials in other mitochondrial disorders.
Reported safety signals	Trials report it as well tolerated over the study periods.	Clinical programmes report injection-site reactions as the most common effect.
A key study	A randomised placebo-controlled trial measured muscle strength and mitochondrial biomarkers with urolithin A in middle-aged adults. (Cell Rep Med 2022, PMID 35584623)	Summarises the September 2025 US accelerated approval of elamipretide for muscle strength in Barth syndrome. (Drugs 2026, PMID 41335372)

WHEN TO RESEARCH WHICH

Urolithin A has supplement-style human trials; SS-31 has drug-development trials. Both are discussed here strictly as research compounds; nothing on this page is medical advice or a dosing guide.

REFERENCES (PUBMED)

[Urolithin A] Urolithin A improves muscle strength, exercise performance, and biomarkers of mitochondrial health in a randomized trial in middle-aged adults — Cell Rep Med 2022. PMID 35584623
[Urolithin A] Effect of Urolithin A Supplementation on Muscle Endurance and Mitochondrial Health in Older Adults: A Randomized Clinical Trial — JAMA Netw Open 2022. PMID 35050355
[Urolithin A] Effect of the mitophagy inducer urolithin A on age-related immune decline: a randomized, placebo-controlled trial — Nat Aging 2025. PMID 41174221
[SS-31] Elamipretide: First Approval — Drugs 2026. PMID 41335372
[SS-31] Elamipretide: A Review of Its Structure, Mechanism of Action, and Therapeutic Potential — Int J Mol Sci 2025. PMID 39940712
[SS-31] The mitochondrial-targeted compound SS-31 re-energizes ischemic mitochondria by interacting with cardiolipin — J Am Soc Nephrol 2013. PMID 23813215

FREQUENTLY ASKED

What is the difference between Urolithin A and SS-31?

Both aim to improve mitochondrial function but at different stages: urolithin A promotes mitophagy, SS-31 stabilises cardiolipin and respiratory function in existing mitochondria.

What is the regulatory status of Urolithin A and SS-31?

Urolithin A: Several randomised human trials in middle-aged and older adults and athletes; marketed as a supplement. SS-31: Accelerated US approval (September 2025) to improve muscle strength in Barth syndrome; further trials in other mitochondrial disorders.

What safety signals have been reported?

Urolithin A: Trials report it as well tolerated over the study periods. SS-31: Clinical programmes report injection-site reactions as the most common effect.

Which studies is this comparison based on?

For Urolithin A: “Urolithin A improves muscle strength, exercise performance, and biomarkers of mitochondrial health in a randomized trial in middle-aged adults” (PMID 35584623); “Effect of Urolithin A Supplementation on Muscle Endurance and Mitochondrial Health in Older Adults: A Randomized Clinical Trial” (PMID 35050355); “Effect of the mitophagy inducer urolithin A on age-related immune decline: a randomized, placebo-controlled trial” (PMID 41174221). For SS-31: “Elamipretide: First Approval” (PMID 41335372); “Elamipretide: A Review of Its Structure, Mechanism of Action, and Therapeutic Potential” (PMID 39940712); “The mitochondrial-targeted compound SS-31 re-energizes ischemic mitochondria by interacting with cardiolipin” (PMID 23813215).