• Milk thistle is a plant whose fruit and seeds are used to make remedies for liver and bile duct ailments (see Question 1 ¹).



• The active ingredient found in milk thistle is silymarin, an antioxidant that protects against cell damage (see Question 1 ¹).



• Milk thistle has been studied in laboratory cell lines and animal tumors for its potential to make chemotherapy less toxic and more effective, and to slow the growth of cancer cells (see Question 3 ² and Question 5 ³).



• Milk thistle is usually taken in capsules or tablets (see Question 4 ⁴).



• No clinical trials using milk thistle or its active compounds in patients with cancer have been published (see Question 6 ⁵).



• Very few bad side effects from the use of milk thistle or silymarin have been reported (see Question 7 ⁶).



• It is not known if milk thistle may make anticancer medications or other drugs more or less effective when taken with them (see Question 7 ⁶).



• The U.S. Food and Drug Administration has not approved the use of milk thistle as a treatment for cancer or any other medical condition (see Question 8 ⁷).



• Milk thistle is available in the United States as an herbal dietary supplement (see Question 8 ⁷).

Glossary Terms

A substance that protects cells from the damage caused by free radicals (unstable molecules made by the process of oxidation during normal metabolism). Free radicals may play a part in cancer, heart disease, stroke, and other diseases of aging. Antioxidants include beta-carotene, lycopene, vitamins A, C, and E, and other natural and manufactured substances.

A tube through which bile passes in and out of the liver.

A term for diseases in which abnormal cells divide without control. Cancer cells can invade nearby tissues and can spread to other parts of the body through the blood and lymph systems. There are several main types of cancer. Carcinoma is cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and multiple myeloma are cancers that begin in the cells of the immune system. Central nervous system cancers are cancers that begin in the tissues of the brain and spinal cord.

In medicine, a sac of tissue and blood vessels that surrounds an organ, joint, or tumor. A capsule is also a form for medicine that is taken by mouth. It usually has a shell made of gelatin with the medicine inside.

The individual unit that makes up the tissues of the body. All living things are made up of one or more cells.

Treatment with drugs that kill cancer cells.

A type of research study that tests how well new medical approaches work in people. These studies test new methods of screening, prevention, diagnosis, or treatment of a disease. Also called a clinical study.

In science, a substance that is made up of more than one ingredient.

Cells of a single type (human, animal, or plant) that have been adapted to grow continuously in the laboratory and are used in research.

A product that is added to the diet. A dietary supplement is taken by mouth, and usually contains one or more dietary ingredient (such as vitamin, mineral, herb, amino acid, and enzyme). Also called nutritional supplement.

Any substance, other than food, that is used to prevent, diagnose, treat or relieve symptoms of a disease or abnormal condition. Also refers to a substance that alters mood or body function, or that can be habit-forming or addictive, especially a narcotic.

FDA. An agency in the U.S. federal government whose mission is to protect public health by making sure that food, cosmetics, and nutritional supplements are safe to use and truthfully labeled. The Food and Drug Administration also makes sure that drugs, medical devices, and equipment are safe and effective, and that blood for transfusions and transplant tissue are safe. Also called FDA.

Having to do with plants.

A large organ located in the upper abdomen. The liver cleanses the blood and aids in digestion by secreting bile.

A plant that has been used in some cultures to treat certain medical problems, including stomach, liver, and gallbladder disorders. The active extract of milk thistle seeds is called silymarin. It is being studied in the prevention of liver damage caused by some cancer treatments. Also called Silybum marianum.

A problem that occurs when treatment affects healthy tissues or organs. Some common side effects of cancer treatment are fatigue, pain, nausea, vomiting, decreased blood cell counts, hair loss, and mouth sores.

A substance obtained from milk thistle seeds that is being studied in the prevention of liver damage caused by certain cancer treatments.

Having to do with poison or something harmful to the body. Toxic substances usually cause unwanted side effects.

An abnormal mass of tissue that results when cells divide more than they should or do not die when they should. Tumors may be benign (not cancerous), or malignant (cancerous). Also called neoplasm.