Ursodeoxycholic acid
Ursodeoxycholic acid (ursodiol), bile acid and mitochondrial stabiliser
Written by Aaron CuhaReviewed Sep 2026
Also known as: UDCA, Ursodiol, Actigall, Urso
An approved bile acid with a genuine mechanism in mitochondrial protection. It failed mouse lifespan testing, and its randomised trial in Parkinson's disease is the more informative result.
Overview
Ursodeoxycholic acid is a naturally occurring bile acid, approved for primary biliary cholangitis and gallstone dissolution, that turned out to have effects beyond the liver. It stabilises mitochondria, reduces endoplasmic reticulum stress and inhibits apoptosis, which made it a candidate for neurodegeneration and for ageing.
In the Interventions Testing Program it produced no significant lifespan effect in either sex.
The more interesting test is in humans. A double-blind randomised placebo-controlled trial in Parkinson's disease was run and published, which puts this compound in a small minority: a repurposed candidate that actually got a proper human trial in a neurodegenerative disease rather than remaining a promising mechanism forever.
Mechanism of action
A hydrophilic secondary bile acid. In cholestatic liver disease it displaces more toxic hydrophobic bile acids from the bile acid pool and stimulates biliary secretion, which is the basis of its approval. Its wider effects come from stabilising mitochondrial membranes and raising the threshold for mitochondrial permeability transition, reducing cytochrome c release and apoptosis, and from reducing endoplasmic reticulum stress. Its taurine conjugate, tauroursodeoxycholic acid, is the form usually studied for neuroprotection and is not identical to the parent compound.
Human evidence
Decades of approved use in cholestatic liver disease, plus a randomised placebo-controlled trial in Parkinson's disease, which is more than most repurposed longevity candidates ever get.
- Established and approved for primary biliary cholangitis, where it improves liver biochemistry and delays progression.
- Approved for gallstone dissolution in selected patients.
- A double-blind randomised placebo-controlled trial was conducted in Parkinson's disease and published in 2023.
- Generally well tolerated, with diarrhoea the most common effect.
- No human study has examined lifespan, healthspan or any ageing endpoint.
What this does not tell you: The liver approvals concern a specific cholestatic disease and do not transfer to healthy ageing. The neuroprotection literature largely concerns the taurine-conjugated form, which is a different molecule from the parent compound, and that distinction is routinely blurred in supplement marketing. The only lifespan test found nothing.
Reading the research record
This compound illustrates a pattern worth naming, because it recurs across this site. A drug is approved for one thing, a plausible second mechanism is discovered, the mechanism attracts attention, and then the question is whether anybody runs the trial. Most candidates never reach that point and circulate indefinitely as mechanisms. This one was actually tested in a randomised placebo-controlled trial in Parkinson's disease, which is the right way for the question to be settled.
For ageing specifically the record is simpler: one rigorous mouse lifespan test, no effect. Anyone taking this or its taurine conjugate as a longevity compound is acting on the mechanism rather than on a result.
The Interventions Testing Program is run by the National Institute on Aging at three independent sites, The Jackson Laboratory, the University of Michigan and the University of Texas Health Science Center at San Antonio. It uses UM-HET3 mice, a genetically heterogeneous four-way cross, so a result cannot be an artefact of one inbred strain. Compounds are fed in the diet, both sexes are tested, cohorts are large enough to detect roughly a 10 percent lifespan change, and results are analysed by log-rank for median survival and by the Wang-Allison test for maximum lifespan. Its nulls are published alongside its positives. That combination of features does not exist anywhere else in ageing research, which is why a null here means considerably more than a null from a single laboratory.
The evidence, charted
Fig. 1 · evidence composition
1of 1 citation (100%) is in people
Every citation cited here is Human work; no other study type is cited on this page. This count is of our own citation list and understates any literature larger than the sources we cite.
Fig. 2 · evidence over time
Every citation here was published in 2023.
Too few distinct publication years on this page to plot as a timeline.
Fig. 3 · legal status at a glance
US
Approved
UK
Approved
AU
Approved
CA
Approved
Approved in all four jurisdictions shown. A jurisdiction's classification is a regulatory fact, not a verdict on the science; see Legal status below for the full text and any notes.
Fig. 4 · dose response
No human dose response curve exists
We draw this figure where the data supports it. For this compound in humans it does not, so the panel stays empty rather than borrowing an animal curve and implying it transfers.
Key studies & citations
- Human2023
A double-blind, randomized, placebo-controlled trial of ursodeoxycholic acid (UDCA) in Parkinson's disease
A randomised double-blind placebo-controlled trial in Parkinson's disease. This is the compound's most rigorous human test outside its approved liver indications, and it is the result that should be read before any mechanistic claim about neuroprotection.
Movement Disorders
Frequently asked questions
Does ursodeoxycholic acid slow ageing?
No evidence supports that. It produced no significant lifespan effect in either sex in multi-site mouse testing, and no human ageing endpoint has been studied. Its approved uses are in cholestatic liver disease.
Is TUDCA the same thing?
Not quite, and the difference matters. Tauroursodeoxycholic acid is the taurine conjugate, it is the form most of the neuroprotection research uses, and it is sold separately as a supplement. Evidence for one does not automatically transfer to the other, and supplement marketing frequently treats them as interchangeable.
What happened in the Parkinson's trial?
A double-blind randomised placebo-controlled trial was completed and published in 2023. It is the compound's most rigorous test outside its liver indications and it is the result to read before accepting any neuroprotection claim, rather than reading the mechanism alone.