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).
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.
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.
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.
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.
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.