Natural Medical SolutionsMilk thistle is a plant. People have used its fruit and seeds for more than 2,000 years, mostly for the liver. The active part is called silymarin.
Is milk thistle approved to treat anything?
No. The FDA has not approved milk thistle as a treatment for cancer, or for any other medical condition.
It is sold as a dietary supplement. The FDA does not approve supplements as safe or as effective. That job falls to the company making the product. They must make sure it is safe and that the label is true.
The FDA does not check how supplements are made either. So one brand may not match another. One batch may not match the last.
What is milk thistle?
Milk thistle grows in Europe, and also in the United States and South America. The fruit and seeds are the parts used.
The seeds contain silymarin. Silymarin is not one substance. It is a mixture, and silybin is its main part. Most research has studied silymarin or silybin, not the whole plant.
It is usually taken by mouth, as a capsule or tablet.
It goes by a lot of names: holy thistle, Marian thistle, Mary thistle, St. Mary thistle and wild artichoke are all the same plant.
What does the research say?
There is an important distinction to make here, so read this part slowly.
The cancer studies did not test milk thistle as a cancer treatment. They tested whether it could reduce the side effects of cancer treatment. Those are very different questions.
What those small studies found:
- In children having chemotherapy for one type of leukemia, silymarin was easier on the liver. It did not get in the way of the chemotherapy.
- In men who had prostate surgery, silymarin with selenium improved quality of life and lowered cholesterol.
- In 30 people having radiation for head and neck cancer, those who took silymarin for six weeks had less mouth soreness.
- In women having radiation for breast cancer, a silymarin cream helped prevent skin rashes.
Away from cancer care, trials have looked at hepatitis, cirrhosis, mushroom poisoning and bile duct problems. Those trials used a wide range of doses. The results were mixed.
In one trial in people with long-term hepatitis, those taking silymarin had fewer symptoms. They also reported a better quality of life.
Silymarin has also helped with iron chelation therapy. That is treatment to remove extra iron from the blood after many transfusions.
What are the side effects of milk thistle?
Very few side effects have been reported. This is one of the better tolerated herbs in this encyclopedia.
Several large studies in people with liver problems found that silymarin may rarely:
- Act as a laxative
- Cause nausea
- Cause heartburn or an upset stomach
At high doses, mild allergic reactions have been seen.
How current is this information?
It is worth knowing that the National Cancer Institute summary this page is based on is no longer being updated. NCI provides it for reference only.
That does not make it wrong. It does mean newer research may exist. If milk thistle matters to a choice you are making, ask your doctor what the evidence looks like now.
Who should talk to a doctor first?
Speak to your doctor before taking milk thistle if any of these apply:
- You are having cancer treatment of any kind
- You have a liver condition
- You are pregnant or breastfeeding
- You take any prescription medicine
If you are in cancer care, do not skip this. Your cancer team needs to know everything you take, supplements included.
Common questions about milk thistle
Does milk thistle treat cancer?
Is milk thistle good for your liver?
What is silymarin?
Does milk thistle have side effects?
Related on this site
Where this information comes from
Written from National Cancer Institute (PDQ patient summary), a public-domain resource from the U.S. National Institutes of Health. Information retrieved 2026-08-21.
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