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Head-to-head

Milk thistle vs TUDCA

The two great liver supplements, and the same lesson twice: the evidence people quote for each belongs to something you are not actually buying.

By Julian RothResearch & dataUpdated October 2026

Short answer

Milk thistle and TUDCA are both over-the-counter supplements with human trial data, so the choice comes down to your goal. Milk thistle suits someone focused on liver support, hangover protection and blood sugar, while TUDCA is aimed at liver health, ER-stress reduction and neuroprotection.

Milk thistle

Silymarin, silibinin, silybin, Silybum marianum

Clinical data

The pooled liver-related mortality benefit (RR 0.50) is not significant once only the high-quality trials are counted (RR 0.57, 95% CI 0.28–1.19), and the best-designed randomized trial found nothing at above-label doses. The respected mushroom-antidote use is intravenous silibinin, not the capsule.

Full Milk thistle evidence review

TUDCA

Tauroursodeoxycholic acid

Clinical data

Real bile-acid chaperone biology with genuine human trial engagement — it was the active component of AMX0035/Relyvrio, which showed a positive phase 2 signal in ALS before its confirmatory phase 3 failed and the drug was withdrawn. The liver/ER-stress mechanism is solid; the clinical outcome record is now a cautionary tale, not a green light.

Full TUDCA evidence review

Milk thistle vs TUDCA: head to head

FDA status / approved use

Milk thistle

Sold as a liver supplement; the intravenous antidote form is not FDA-approved in the US

TUDCA

Sold as a dietary supplement, not an approved drug; its relative UDCA is an approved medicine
Marketed for

Milk thistle

Liver support and 'detox', hangover protection, blood sugar

TUDCA

Liver health, ER-stress reduction, neuroprotection
Outcome areas

Milk thistle

Liver / detox; Blood sugar / insulin sensitivity

TUDCA

Liver / detox; Cognitive function / memory
Evidence grade

Milk thistle

Clinical data

TUDCA

Clinical data
How it works

Milk thistle

mTOR & other

TUDCA

Chemical chaperone that eases endoplasmic-reticulum stress in cells
Route and dosing

Milk thistle

Oral silymarin extract capsule

TUDCA

Oral capsule
Headline human result

Milk thistle

No significant effect on ALT, viral load or quality of life in an RCT of 154 hepatitis C patients

TUDCA

About 30% higher liver and muscle insulin sensitivity after four weeks at 1,750 mg/day in a 2010 study of 20 obese adults
Strongest evidence

Milk thistle

Cochrane review, 18 RCTs / 1,088 patients, 2007Milk thistle evidence reviewPubMed 17943794

TUDCA

AMX0035 phase 2/3 ALS trial, NEJM 2020TUDCA evidence reviewPubMed 32877582
Key safety signal

Milk thistle

Considered safe; adverse events matched placebo in the largest trial

TUDCA

Small studies suggest it is at least as well tolerated as UDCA; no long-term data
How it is obtained

Milk thistle

Over the counter as a dietary supplement

TUDCA

Over the counter as a dietary supplement

marks a row where the two differ. “Not established” marks a cell the available evidence does not answer. Evidence grades come from our evidence matrix, which grades each molecule on the human data for the use it is marketed for.

Clinical data:
Tested in humans — but investigational, discontinued, or proven only on a surrogate marker (not the marketed outcome).

Our verdict

Neither supports the liver-support claim it is sold on, and both fail in the same instructive way — by borrowing credibility from a relative. Milk thistle's pooled liver-related mortality benefit (RR 0.50) stops being significant once only the high-quality trials are counted, its best-designed randomized trial found nothing at above-label doses, and the mushroom-poisoning use everyone cites is intravenous silibinin given in hospital, not a capsule. TUDCA's borrowed credibility is its parent compound: it is UDCA, not TUDCA, that became an approved drug with randomized-trial support in primary biliary cholangitis, and TUDCA's own most ambitious human program — the ALS combination Relyvrio — failed phase 3 and was withdrawn in 2024. Milk thistle has the larger trial base and the clearer null; TUDCA has the better mechanism and the more serious drug behind it.

Milk thistle fits if

You want the cheaper, older option with the larger randomized literature behind it — as long as you read that literature as the null it mostly is, and not as the intravenous antidote.

TUDCA fits if

The ER-stress mechanism is what interests you, and you understand the strong liver evidence belongs to UDCA, the approved parent drug, rather than to the supplement in the bottle.

Milk thistle vs TUDCA: common questions

Is either milk thistle or TUDCA FDA-approved?
No. Milk thistle is sold as a liver supplement; the intravenous antidote form is not FDA-approved in the US. TUDCA is sold as a dietary supplement, not an approved drug; its relative UDCA is an approved medicine.
Which has stronger human evidence, milk thistle or TUDCA?
Neither clearly. Both have human clinical data. The key source for milk thistle is Cochrane review, 18 RCTs / 1,088 patients, 2007; for TUDCA, it is AMX0035 phase 2/3 ALS trial, NEJM 2020.
What are the main safety concerns with milk thistle and TUDCA?
Milk thistle is considered safe; adverse events matched placebo in the largest trial. With TUDCA, small studies suggest it is at least as well tolerated as UDCA; no long-term data.

Key studies behind each

Milk thistle

  1. Fried MW, Navarro VJ, Afdhal N, et al.; Silymarin in NASH and C Hepatitis (SyNCH) Study Group. (2012). Effect of silymarin (milk thistle) on liver disease in patients with chronic hepatitis C unsuccessfully treated with interferon therapy: a randomized controlled trial. JAMA. PubMed 22797645
  2. Rambaldi A, Jacobs BP, Gluud C. (2007). Milk thistle for alcoholic and/or hepatitis B or C virus liver diseases. Cochrane Database Syst Rev. PubMed 17943794
  3. Wah Kheong C, Nik Mustapha NR, Mahadeva S. (2017). A Randomized Trial of Silymarin for the Treatment of Nonalcoholic Steatohepatitis. Clin Gastroenterol Hepatol. PubMed 28419855
  4. Voroneanu L, Nistor I, Dumea R, Apetrii M, Covic A. (2016). Silymarin in Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. J Diabetes Res. PubMed 27340676

TUDCA

  1. Poupon RE, Balkau B, Eschwège E, Poupon R; UDCA-PBC Study Group. (1991). A multicenter, controlled trial of ursodiol for the treatment of primary biliary cirrhosis. N Engl J Med. PubMed 1674105
  2. Ozcan U, Yilmaz E, Ozcan L, et al. (2006). Chemical chaperones reduce ER stress and restore glucose homeostasis in a mouse model of type 2 diabetes. Science. PubMed 16931765
  3. Kars M, Yang L, Gregor MF, et al. (2010). Tauroursodeoxycholic acid may improve liver and muscle but not adipose tissue insulin sensitivity in obese men and women. Diabetes. PubMed 20522594
  4. Paganoni S, Macklin EA, Hendrix S, et al. (2020). Trial of Sodium Phenylbutyrate-Taurursodiol for Amyotrophic Lateral Sclerosis. N Engl J Med. PubMed 32877582

The full evidence reviews

  • Milk thistle: the effect fades as the trials improve

    Milk thistle's pooled liver-mortality benefit disappears in the high-quality trials, and its best-designed randomized trial found nothing at above-label doses — while the famous mushroom-poisoning antidote is an intravenous hospital drug, not the capsule on the shelf.

    Updated August 2026

  • TUDCA: real bile-acid biology, an approved parent drug, and a failed flagship trial

    TUDCA is a genuine ER-stress-calming chemical chaperone whose parent compound (UDCA/ursodiol) is an approved liver drug — but the longevity and broad supplement claims rest on mechanism and small or animal studies, and its highest-profile human program (ALS / Relyvrio) failed phase 3 and was withdrawn in 2024.

    Updated August 2026

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