Milk thistle

Also called: silymarin, Silybum marianum.

Last reviewed 2026-09-16. How this works.

Protecting the liver during treatment Grade C

Human evidence exists and does not settle it.

A small trial in children found a possible liver benefit weeks later, but nothing at the first check.

One small randomised trial, with a borderline result at delayed follow-up.

The claim

The claim is that milk thistle protects the liver from the damage some chemotherapy causes. It is one of the few supplement claims in this book aimed at a side effect rather than at the cancer.

What it does

Silymarin has been used for liver conditions for a long time and there is a reasonable pharmacological basis for the claim.

The evidence

A randomised, double-blind pilot trial enrolled 50 children with acute lymphoblastic leukaemia and chemotherapy-related liver toxicity. Twenty-four were allocated to milk thistle and 26 to placebo, and one child declined, leaving 23 and 26 analysed.1

There was no difference at the first follow-up point. At the later one, the milk thistle group had a lower level of one liver enzyme, reported as P=0.05 in the abstract and marked P=0.04 on the figure, with a trend in a second enzyme. Chemotherapy reductions were less frequent in the milk thistle group, but not significantly so.1

The most useful part of this study is the part that is not about efficacy. Its authors also tested in the laboratory whether milk thistle antagonised the chemotherapy the children were receiving, and found it did not. Somebody checked the interaction worry in the specific setting rather than assuming it either way.1

The studies this rests on

  • Milk thistle for chemotherapy-related liver toxicity in childhood leukaemia1

    A randomised trial, double blind, phase 2, measured a laboratory marker, not an outcome, 50 participants.

    no difference at the first follow-up; a lower liver enzyme level at the later one, borderline significance.

What is absent

This is a single pilot trial in children with one cancer. It has not been repeated, and it was not designed to settle the question.

Scope: any age group, any tumour type.

Established by trial scope, checked 2026-09-16. Result: the only trial in this record describes itself as a pilot study.1

What to ask

Is my liver something you are watching during this treatment, and would you want to know what I take for it?

The dish-to-person gap

The register holds no human pharmacokinetic measurement for silymarin against any laboratory concentration.

When to call your team — no warning signs are recorded

Whatever you are taking or thinking of taking, the people treating you can only weigh it if they know about it. That is true when nothing has been written down here, and it is most true then.

The register records no warning signs for milk thistle. That is not a statement that nothing can go wrong.

Interactions

This is one of the few entries where somebody actually checked. In laboratory work within the same trial, no antagonism was found between milk thistle and vincristine or L-asparaginase, with a modest synergy for vincristine. That is a narrow finding in one setting, and it is more than most entries here can say.1

The whole interaction list, and how to turn it into a pharmacy review request.

Find a trial instead

The existing trial was a pilot, and a larger one is the obvious next step.

Search ClinicalTrials.gov for recruiting studies of silymarin OR milk thistle

A trial is the same decision with monitoring, a known preparation and a doctor who knows what else you are taking.

References

  1. Ladas EJ, Kroll DJ, Oberlies NH, Cheng B, Ndao DH, Rheingold SR, Kelly KM. A randomized controlled, double-blind pilot study of milk thistle for the treatment of hepatotoxicity in childhood acute lymphoblastic leukemia. Cancer 2010 Jan 15;116(2):506-513.

    doi:10.1002/cncr.24723 · PubMed 20014183 · PMC3542639

    How this was reached: transcribed from chapter note, via docs/CHAPTER-NOTES.json, chapter 18 note 7.

    Held against this source and not confirmed:

    • the day 56 aspartate aminotransferase P value

      Reported as P=0.05 in the abstract and marked P=0.04 on the figure in the same paper. Both are recorded; neither is presented as definitive.