Milk Thistle (PDQ®)–Patient Version

NOTE: There is either no new research on this topic or the recent published research is weak and not appropriate for inclusion in the summary. Therefore, the information in this summary is no longer being updated and is provided for reference purposes only.

1. What is milk thistle?

   Milk thistle is a plant whose fruit and seeds have been used for more than 2,000 years as a treatment for liver and bile duct disorders. Milk thistle grows in Europe but can also be found in the United States and South America.

   Silymarin, found in milk thistle seeds, is a mixture that contains compounds, such as silybin, isosilybin, silychristin and isosilychristin, silydianin, and taxifolin. Most studies have been done in silymarin or silybin, instead of the whole plant.

   The botanical name for milk thistle is Silybum marianum. Milk thistle is also called holy thistle, Marian thistle, Mary thistle, St. Mary thistle, Our Lady's thistle, wild artichoke, Mariendistel (German), and Chardon-Marie (French).

2. How is milk thistle taken or given?

   Milk thistle is usually taken by mouth in capsules or tablets. In Europe silybin is given by intravenous infusion as the only treatment for Amanita phalloides, a mushroom toxin that causes death.

3. Have any laboratory or animal studies been done using milk thistle?

   In laboratory studies, tumor cells are used to test a substance to find out if it is likely to have any anticancer effects. In animal studies, tests are done to see if a drug, procedure, or treatment is safe and effective in animals. Laboratory and animal studies are done before a substance is tested in people.

   Laboratory and animal studies have tested the effects of milk thistle in laboratory experiments. Silymarin, the active substance found in milk thistle seeds, and silybin A and B, the major components of silymarin, have been studied in laboratory research. See the Laboratory/Animal/Preclinical Studies section of the health professional version of Milk Thistle for information on laboratory and animal studies done using milk thistle.

4. Have any studies of milk thistle been done in people?

   Several small studies have looked at whether milk thistle can be used to decrease side effects of cancer treatment.

   • A randomized clinical trial in children with acute lymphoblastic leukemia found that silymarin decreased the side effects of chemotherapy on the liver without harming the cancer treatment.
   • A randomized clinical trial in men with prostate cancer who had surgery to remove their prostate found that taking silymarin and selenium improved quality of life, lowered cholesterol, and increased the amount of selenium in the blood.
   • A randomized clinical trial of 30 patients with head and neck cancer who had radiation therapy found that those who took silymarin for 6 weeks had lower rates of radiation-related mucositis compared to those who did not.
   • A nonrandomized observational study in women with breast cancer who had surgery and radiation therapy found that a silymarin-based cream helped prevent patients from having skin rashes from radiation therapy.

   A number of clinical trials have studied milk thistle in the treatment of patients with hepatitis, cirrhosis, mushroom poisoning, or bile duct disorders. These trials have used a wide range of doses with mixed results. In a trial of biologic therapy for patients with chronic hepatitis, patients taking silymarin had less symptoms and a better quality of life compared to patients not taking silymarin.

   Silymarin has been found to help with iron chelation therapy, which removes extra iron in the blood of patients who have had many blood transfusions.

5. Have any side effects or risks been reported from milk thistle?

   Very few side effects from the use of milk thistle or silymarin have been reported. Several large studies in patients with liver disorders have found that taking silymarin may rarely have a laxative effect or cause nausea, heartburn, or stomach upset. At high doses, mild allergic reactions have been seen.

6. Is milk thistle approved by the U.S. Food and Drug Administration (FDA) for use as a cancer treatment in the United States?

   The U.S. Food and Drug Administration (FDA) has not approved the use of milk thistle as a treatment for cancer or any other medical condition.

   The FDA does not approve dietary supplements as safe or effective. The company that makes the dietary supplements is responsible for making sure they are safe and that the claims on the label are true and do not mislead the consumer. The way that supplements are made is not regulated by the FDA, so all batches and brands of milk thistle supplements may not be the same.

Use our clinical trial search to find NCI-supported cancer clinical trials that are accepting patients. You can search for trials based on the type of cancer, the age of the patient, and where the trials are being done. General information about clinical trials is also available.

Complementary and alternative medicine (CAM)—also called integrative medicine—includes a broad range of healing philosophies, approaches, and therapies. A therapy is generally called complementary when it is used in addition to conventional treatments; it is often called alternative when it is used instead of conventional treatment. (Conventional treatments are those that are widely accepted and practiced by the mainstream medical community.) Depending on how they are used, some therapies can be considered either complementary or alternative. Complementary and alternative therapies are used in an effort to prevent illness, reduce stress, prevent or reduce side effects and symptoms, or control or cure disease.

Unlike conventional treatments for cancer, complementary and alternative therapies are often not covered by insurance companies. Patients should check with their insurance provider to find out about coverage for complementary and alternative therapies.

Cancer patients considering complementary and alternative therapies should discuss this decision with their doctor, nurse, or pharmacist as they would any type of treatment. Some complementary and alternative therapies may affect their standard treatment or may be harmful when used with conventional treatment.

It is important that the same scientific methods used to test conventional therapies are used to test CAM therapies. The National Cancer Institute and the National Center for Complementary and Integrative Health (NCCIH) are sponsoring a number of clinical trials (research studies) at medical centers to test CAM therapies for use in cancer.

Conventional approaches to cancer treatment have generally been studied for safety and effectiveness through a scientific process that includes clinical trials with large numbers of patients. Less is known about the safety and effectiveness of complementary and alternative methods. Few CAM therapies have been tested using demanding scientific methods. A small number of CAM therapies that were thought to be purely alternative approaches are now being used in cancer treatment—not as cures, but as complementary therapies that may help patients feel better and recover faster. One example is acupuncture. According to a panel of experts at a National Institutes of Health (NIH) meeting in November 1997, acupuncture has been found to help control nausea and vomiting caused by chemotherapy and pain related to surgery. However, some approaches, such as the use of laetrile, have been studied and found not to work and to possibly cause harm.

The NCI Best Case Series Program which was started in 1991, is one way CAM approaches that are being used in practice are being studied. The program is overseen by the NCI’s Office of Cancer Complementary and Alternative Medicine (OCCAM). Health care professionals who offer alternative cancer therapies submit their patients’ medical records and related materials to OCCAM. OCCAM carefully reviews these materials to see if any seem worth further research.

When considering complementary and alternative therapies, patients should ask their health care provider the following questions:

National Center for Complementary and Integrative Health (NCCIH)

The National Center for Complementary and Integrative Health (NCCIH) at the National Institutes of Health (NIH) facilitates research and evaluation of complementary and alternative practices, and provides information about a variety of approaches to health professionals and the public.

CAM on PubMed

NCCIH and the NIH National Library of Medicine (NLM) jointly developed CAM on PubMed, a free and easy-to-use search tool for finding CAM-related journal citations. As a subset of the NLM's PubMed bibliographic database, CAM on PubMed features more than 230,000 references and abstracts for CAM-related articles from scientific journals. This database also provides links to the websites of over 1,800 journals, allowing users to view full-text articles. (A subscription or other fee may be required to access full-text articles.)

Office of Cancer Complementary and Alternative Medicine

The NCI Office of Cancer Complementary and Alternative Medicine (OCCAM) coordinates the activities of the NCI in the area of complementary and alternative medicine (CAM). OCCAM supports CAM cancer research and provides information about cancer-related CAM to health providers and the general public via the NCI website.

National Cancer Institute (NCI) Cancer Information Service

U.S. residents may call the Cancer Information Service (CIS), NCI's contact center, toll free at 1-800-4-CANCER (1-800-422-6237) Monday through Friday from 9:00 am to 9:00 pm. A trained Cancer Information Specialist is available to answer your questions.

Food and Drug Administration

The Food and Drug Administration (FDA) regulates drugs and medical devices to ensure that they are safe and effective.

Federal Trade Commission

The Federal Trade Commission (FTC) enforces consumer protection laws. Publications available from the FTC include: