Milk thistle and cancer

Milk thistle is a plant that comes from the same group of flowers as the daisy. It is not a treatment for cancer.


  • The medicinal compound in milk thistle is silymarin, an extract of milk thistle seeds.
  • Milk thistle might help to treat some liver diseases such as hepatitis and cirrhosis.
  • More research is needed before we will know if milk thistle can help prevent or treat cancer. 

What is milk thistle?

People have been using the fruit and seeds of the milk thistle plant for hundreds of years. They use them as a herbal remedy for some liver problems. 

The scientific name for milk thistle is Silybum marianum. It has many other names. This includes lady’s thistle, St Mary’s thistle, holy thistle and variegated artichoke.

The medicinal compound in milk thistle is silymarin, an extract of milk thistle seeds. It is an antioxidant that protects against cell damage.

Silymarin contains at least 4 major compounds, including silybin (the most active), isosilybin, silychristin, and silydianin. Most research has studied silymarin or its major compound silybin.

How you have it

Milk thistle supplements are available as capsules, tablets, powder and liquid extract.

Powdered milk thistle can be made into a tea. 

Side effects

Milk thistle is generally considered safe. But check with you doctor first before taking it.

Women who are pregnant or breast feeding should not take this herb. If you are diabetic you should consult your doctor first. 

Rarely, milk thistle can cause diarrhoea, feeling sick and heartburn.

If you have liver problems you should consult your doctor first. High doses of the herb can cause elevated levels of bilirubin and liver enzymes. 

We need more research looking at how milk thistle might affect cancer treatments. 

Generally antioxidant supplements are not recommended during chemotherapy or radiotherapy treatment. This is because they may block some of the cancer killing effects of these treatments.

Research into milk thistle and cancer

Research in the laboratory has shown that milk thistle might help to treat some liver diseases, such as hepatitis and cirrhosis. 

A few trials have looked at milk thistle for people with cancer.

A number of companies on the internet claim that milk thistle can help to detoxify and protect your liver. They also claim that it can help to protect other organs of the body such as the gallbladder and spleen.

Some claim that it slows the growth of some types of cancer, including breast and prostate cancer.

It is possible that milk thistle may play a part in treating liver disease and some types of cancer. But we need a lot more research with larger numbers of people first. Reliable clinical trials can find out how useful milk thistle might be in preventing or treating cancer.

A word of caution

Make sure you check with your cancer specialist before you start taking milk thistle. They know about your individual situation, so can give you advice. 

  • National Cancer Institute (NCI).

  • Topical silymarin administration for prevention of acute radiodermatitis in breast cancer patients: A randomized, double‐blind, placebo‐controlled clinical trial
    H. Karbasforooshan and others
    Phytotherapy Research, February 2019, Vol 33, Issue 2, Pages 379-386

  • Dietary Supplement Use During Chemotherapy and Survival Outcomes of Patients With Breast Cancer Enrolled in a Cooperative Group Clinical Trial (SWOG S0221)
    C Ambrosone and others 
    Journal of Clinical Oncology, 2020. Volume 38, Issue 8

  • Protective Role of Silymarin on Hepatic and Renal Toxicity Induced by MTX Based Chemotherapy in Children with Acute Lymphoblastic Leukemia
    A Hagag and others
    Mediterranean Journal of Hematology and Infectious Diseases, 2016. Volume 8, Issue 1

  • Milk thistle for alcoholic and/or hepatitis B or C virus liver diseases
    A. Rambaldi
    The Cochrane database of systematic reviews, Oct 2007

  • Effect of silymarin in the prevention of Cisplatin nephrotoxicity, a clinical trial study
    A Momeni and others 
    Journal of Clinical and Diagnostic Research, 2015. Volume 9, Issue 4

  • The information on this page is based on literature searches and specialist checking. We used many references and there are too many to list here. If you need additional references for this information please contact with details of the particular issue you are interested in.

Last reviewed: 
18 Aug 2022
Next review due: 
18 Aug 2025

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