Overview
Questions and Answers About Milk Thistle
Changes to This Summary (06/07/2007)
General CAM Information
Evaluation of CAM Approaches
Questions to Ask Your Health Care Provider About CAM
To Learn More About CAM

Overview

• 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).

Questions and Answers About Milk Thistle

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 disorders of the liver, bile ducts, and gallbladder. Milk thistle is native to Europe but can also be found in the United States and South America.

   The medicinal ingredient found in milk thistle is silymarin, an extract of milk thistle seeds. It is an antioxidant that protects against cell damage. Silymarin contains 4 compounds: silybin (the most active), isosilybin, silychristin, and silydianin. Most research has studied silymarin or its major compound silybin, instead of the plant in its whole form.

   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. What is the history of the discovery and use of milk thistle as a complementary and alternative treatment for cancer?

   The ancient Greeks and Romans used milk thistle as a treatment for liver ailments and snake bites. During the Middle Ages, milk thistle was recommended to treat liver toxins. Modern homeopathic practitioners have used compounds from milk thistle seeds to treat a range of disorders including jaundice, gallstones, and peritonitis. The German Commission E, which studies the safety and efficacy of herbs for the German government, recommends milk thistle for liver damage due to toxins, cirrhosis of the liver, and as a supportive therapy for chronic inflammation of the liver.

   Despite milk thistle's long history of use for liver complaints, it was not until 1968 that researchers extracted silymarin from milk thistle seeds and suggested that it might be the plant's active ingredient. Silymarin was later discovered to be a mixture of flavonolignans, a family of plant-based substances with antioxidant effects.

3. What is the theory behind the claim that milk thistle is useful in treating cancer?

   To research the claim that milk thistle is useful in treating cancer, its active substance silymarin and its major compound silybin have been the most widely studied ingredients.

   Silymarin and silybin may protect the liver against damage from toxic chemicals by blocking toxins from entering the cell or by moving toxins out of the cell before damage begins.

   Silymarin and silybin have been studied in the laboratory in cancer cells as well as in animal tumors of the tongue, skin, bladder, colon, and small intestine. They have been tested for their potential to:

   • Make chemotherapy less toxic.
   • Make chemotherapy more effective.
   • Stop or slow the growth of cancer cells and block tumors from starting or continuing to grow.
   • Help to repair liver tissue.

   Although the findings of many of these laboratory studies have been promising, none of the results have been shown in human clinical trials.

4. How is milk thistle administered?

   Milk thistle is usually taken by mouth in capsules or tablets. Since it does not dissolve well in water, it is not commonly taken as an herbal tea. In Europe, the active compound silybin is given by intravenous infusion as the only effective antidote for Amanita phalloides, a rare mushroom toxin that causes deadly liver failure.

   Most milk thistle supplements are measured by how much silybin they contain. Special forms of silybin made to be easily absorbed and used by the body are sold under the names Legalon, silipide, and Siliphos.

5. Have any preclinical (laboratory or animal) studies been conducted using milk thistle?

   Research in a laboratory or using animals is done to find out if a drug, procedure, or treatment is likely to be useful in humans. Preclinical studies are done before clinical trials (in humans) are begun.

   Silymarin, the active substance found in milk thistle seeds, has been studied in laboratory research. These studies have shown that it acts as an antioxidant by:

   • Strengthening cell walls to prevent toxins from crossing into the cell.
   • Stimulating enzymes that make toxins less harmful to the body.
   • Blocking damaging substances called free radicals from attacking cells.

   Silybin, the major compound found in silymarin, has been studied in laboratory experiments using cancer cell lines (cells adapted to grow in the laboratory). These studies show that silybin:

   • May help cisplatin and doxorubicin (chemotherapy drugs) work better against ovarian and breast cancer cells.
   • May have direct anticancer effects against prostate, breast, and cervical cancer cells.
   • May slow down cell growth, as shown in prostate cancer cell lines.
6. Have any clinical trials (research studies with people) of milk thistle been conducted?

   No clinical trials using milk thistle or its active compounds in patients with cancer have been published. To do clinical drug research in the United States, researchers must file a confidential Investigational New Drug (IND) application with the Food and Drug Administration (FDA). To date, only 1 researcher has made public an IND to study milk thistle as an adjunct cancer treatment.

   There is 1 case report describing the use of silymarin in a patient with promyelocytic leukemia who required breaks in chemotherapy due to abnormal liver enzyme levels. During 4 months of treatment with silymarin, the patient had normal liver enzyme levels and was able to undergo chemotherapy without breaks. A second case report describes a patient with hepatocellular carcinoma whose symptoms improved when he took 450 milligrams of silymarin per day, without anticancer therapy. These case report findings have not been shown in a clinical trial.

   A number of clinical trials have, however, studied milk thistle or silymarin in the treatment of patients with hepatitis, cirrhosis, or disorders of the bile ducts. These trials have used a wide range of doses with mixed results. The beneficial effects of silymarin shown in some studies suggest it might play a role in preventing hepatitis and/or liver cancer, but no clinical trials have studied the use of silymarin for prevention.

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

   Very few bad side effects from the use of milk thistle or silymarin have been reported when taken as recommended. Several large, carefully designed 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 (more than 1,500 milligrams a day).

   Silymarin has been used in pregnant women who have a bile blockage in the liver, with no toxic effects to the patient or fetus. Silymarin have also been given to children intravenously for mushroom poisoning.

   It is not known if milk thistle may make anticancer medications or other drugs more effective, less effective, or have no effect when taken with them.

8. 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 has not approved the use of milk thistle as a treatment for cancer or any other medical condition.

   Milk thistle is available in the United States as a dietary supplement. Because dietary supplements are regulated as foods, not as drugs, FDA approval is not required unless specific claims about disease prevention or treatment are made.

   Given the limited research done with milk thistle in patients with cancer, using it as a cancer treatment cannot be recommended except in carefully designed clinical trials.

Changes to This Summary (06/07/2007)

The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.

Editorial changes were made to this summary.

General CAM Information

Complementary and alternative medicine (CAM)—also referred to as 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 therapeutic approach, because some complementary and alternative therapies may interfere with their standard treatment or may be harmful when used with conventional treatment.

Evaluation of CAM Approaches

It is important that the same rigorous scientific evaluation used to assess conventional approaches be used to evaluate CAM therapies. The National Cancer Institute (NCI) and the National Center for Complementary and Alternative Medicine (NCCAM) are sponsoring a number of clinical trials (research studies) at medical centers to evaluate CAM therapies for cancer.

Conventional approaches to cancer treatment have generally been studied for safety and effectiveness through a rigorous 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 undergone rigorous evaluation. A small number of CAM therapies originally considered to be purely alternative approaches are finding a place 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) Consensus Conference in November 1997, acupuncture has been found to be effective in the management of chemotherapy-associated nausea and vomiting and in controlling pain associated with surgery. In contrast, some approaches, such as the use of laetrile, have been studied and found ineffective or potentially harmful.

The NCI Best Case Series Program ⁸, which was started in 1991, is one way CAM approaches that are being used in practice are being investigated. 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 conducts a critical review of the materials and develops follow-up research strategies for approaches deemed to warrant NCI-initiated research.

Questions to Ask Your Health Care Provider About CAM

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

• What side effects can be expected?
• What are the risks associated with this therapy?
• Do the known benefits outweigh the risks?
• What benefits can be expected from this therapy?
• Will the therapy interfere with conventional treatment?
• Is this therapy part of a clinical trial?
• If so, who is sponsoring the trial?
• Will the therapy be covered by health insurance?

To Learn More About CAM

National Center for Complementary and Alternative Medicine (NCCAM)

The National Center for Complementary and Alternative Medicine (NCCAM) 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.

NCCAM Clearinghouse

Post Office Box 7923 Gaithersburg, MD 20898–7923

Telephone: 1–888–644–6226 (toll free) 301–519–3153 (for International callers)

TTY (for deaf and hard of hearing callers): 1–866–464–3615

Fax: 1–866–464–3616

E-mail: info@nccam.nih.gov

Web site: http://nccam.nih.gov

CAM on PubMed

NCCAM 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 Web sites 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.) CAM on PubMed is available through the NCCAM Web site ⁹. It can also be accessed through NLM PubMed ¹⁰ bibliographic database by selecting the "Limits" tab and choosing "Complementary Medicine" as a subset.

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 Web site ¹¹.

National Cancer Institute (NCI) Cancer Information Service

U.S. residents may call the NCI Cancer Information Service toll free at 1-800-4-CANCER (1-800-422-6237) Monday through Friday from 9:00 am to 4:30 pm. Deaf and hearing impaired callers with TTY equipment may call 1-800-332-8615. 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.

Food and Drug Administration

5600 Fishers Lane

Rockville, MD 20857

Telephone: 1–888–463–6332 (toll free)

Web site: http://www.fda.gov/

Federal Trade Commission

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

• Who Cares: Sources of Information About Health Care Products and Services
• Fraudulent Health Claims: Don’t Be Fooled

Consumer Response Center

Federal Trade Commission

CRC-240

Washington, DC 20580

Telephone: 1-877-FTC-HELP (1-877-382-4357) (toll free)

TTY (for deaf and hearing impaired callers): 202-326-2502

Web site: http://www.ftc.gov/

Glossary Terms

Not normal. An abnormal lesion or growth may be cancerous, premalignant (likely to become cancer), or benign.

Another treatment used together with the primary treatment. Its purpose is to assist the primary treatment. Also called adjunctive therapy.

A hypersensitive immune reaction to a substance that normally is harmless or would not cause an immune response in most people. An allergic response may cause harmful symptoms such as itching or inflammation or tissue injury.

A type of poisonous mushroom that has harmful effects on the kidneys and liver. It is responsible for most fatal cases of mushroom poisoning. Also called death cap.

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.

The organ that stores urine.

Having to do with, or derived from, plants.

Cancer that forms in tissues of the breast, usually the ducts (tubes that carry milk to the nipple) and lobules (glands that make milk). It occurs in both men and women, although male breast cancer is rare.

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.

A detailed report of the diagnosis, treatment, and follow-up of an individual patient. Case reports also contain some demographic information about the patient (for example, age, gender, ethnic origin).

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

Cancer that forms in tissues of the cervix (the organ connecting the uterus and vagina). It is usually a slow-growing cancer that may not have symptoms but can be found with regular Pap tests (a procedure in which cells are scraped from the cervix and looked at under a microscope).

Treatment with drugs that kill cancer cells.

A disease or condition that persists or progresses over a long period of time.

A type of chronic, progressive liver disease in which liver cells are replaced by scar tissue.

A drug used to treat many types of cancer. Cisplatin contains the metal platinum. It kills cancer cells by damaging their DNA and stopping them from dividing. Cisplatin is a type of alkylating agent.

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 clinical study.

The longest part of the large intestine, which is a tube-like organ connected to the small intestine at one end and the anus at the other. The colon removes water and some nutrients and electrolytes from partially digested food. The remaining material, solid waste called stool, moves through the colon to the rectum and leaves the body through the anus.

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.

In medicine, a disturbance of normal functioning of the mind or body. Disorders may be caused by genetic factors, disease, or trauma.

The amount of medicine taken, or radiation given, at one time.

A drug that is used to treat many types of cancer and is being studied in the treatment of other types of cancer. Doxorubicin comes from the bacterium Streptomyces peucetius. It damages DNA (the molecules inside cells that carry genetic information) and stops cells from growing. Rapidly growing tumor cells that take up doxorubicin may die. It is a type of anthracycline antitumor antibiotic. Also called Adriamycin PFS, Adriamycin RDF, doxorubicin hydrochloride, and Rubex.

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.

Effectiveness. In medicine, the ability of an intervention (for example, a drug or surgery) to produce the desired beneficial effect.

A protein that speeds up chemical reactions in the body.

In medicine, a preparation of a substance obtained from plants, animals, or bacteria and used as a drug or in drugs.

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 FDA 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 Food and Drug Administration.

The developing offspring from 7 to 8 weeks after conception until birth.

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.

A highly reactive chemical that often contains oxygen and is produced when molecules are split to give products that have unpaired electrons (a process called oxidation). Free radicals can damage important cellular molecules such as DNA or lipids or other parts of the cell.

The pear-shaped organ found below the liver. Bile is concentrated and stored in the gallbladder.

Solid material that forms in the gallbladder or common bile duct. Gallstones are made of cholesterol or other substances found in the gallbladder. They may occur as one large stone or as many small ones, and vary from the size of a golf ball to a grain of sand. Also called cholelith.

The German Federal Institute for Drugs and Medical Devices Commission E. A committee made up of scientists, toxicologists, doctors, and pharmacists formed by the German government in 1978 to find out if herbs sold in Germany are safe and effective. The Commission has published information on the uses, side effects, and drug interactions of more than 300 herbs.

Disease of the liver causing inflammation. Symptoms include an enlarged liver, fever, nausea, vomiting, abdominal pain, and dark urine.

A type of adenocarcinoma, the most common type of liver tumor.

Having to do with plants.

A plant whose leaves, stems, and flowers have been used in some cultures to treat certain medical problems. Holy thistle may have anti-inflammatory and anticancer effects. The scientific name is Cnicus benedictus. Also called blessed thistle, cardin, spotted thistle, and St. Benedict's thistle.

An alternative approach to medicine based on the belief that natural substances, prepared in a special way and used most often in very small amounts, restore health. According to these beliefs, in order for a remedy to be effective, it must cause in a healthy person the same symptoms being treated in the patient. Also called homeopathy.

Redness, swelling, pain, and/or a feeling of heat in an area of the body. This is a protective reaction to injury, disease, or irritation of the tissues.

Into or within a vein. Intravenous usually refers to a way of giving a drug or other substance through a needle or tube inserted into a vein. Also called I.V..

A method of putting fluids, including drugs, into the bloodstream. Also called infusion.

A condition in which the skin and the whites of the eyes become yellow, urine darkens, and the color of stool becomes lighter than normal. Jaundice occurs when the liver is not working properly or when a bile duct is blocked.

Research done in a laboratory. These studies may use test tubes or animals to find out if a drug, procedure, or treatment is likely to be useful. Laboratory studies take place before any testing is done in humans.

A substance that promotes bowel movements.

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

Primary liver cancer is cancer that forms in the tissues of the liver. Secondary liver cancer is cancer that spreads to the liver from another part of the body.

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 measure of weight. A milligram is approximately 450,000 times smaller than a pound and 28,000 times smaller than an ounce.

A feeling of sickness or discomfort in the stomach that may come with an urge to vomit. Nausea is a side effect of some types of cancer therapy.

Cancer that forms in tissues of the ovary (one of a pair of female reproductive glands in which the ova, or eggs, are formed). Most ovarian cancers are either ovarian epithelial carcinomas (cancer that begins in the cells on the surface of the ovary) or malignant germ cell tumors (cancer that begins in egg cells).

PDQ is an online database developed and maintained by the National Cancer Institute. Designed to make the most current, credible, and accurate cancer information available to health professionals and the public, PDQ contains peer-reviewed summaries on cancer treatment, screening, prevention, genetics, complementary and alternative medicine, and supportive care; a registry of cancer clinical trials from around the world; and directories of physicians, professionals who provide genetics services, and organizations that provide cancer care. Most of this information, and more specific information about PDQ, can be found on the NCI's Web site at http://www.cancer.gov/cancertopics/pdq. Also called Physician Data Query.

Inflammation of the peritoneum (tissue that lines the abdominal wall and covers most of the organs in the abdomen). Peritonitis can result from infection, injury, or certain diseases. Symptoms may include swelling of the abdomen, severe pain, and weight loss.

A person who works in a specific profession. For example, a doctor or nurse is a healthcare practitioner.

Research using animals to find out if a drug, procedure, or treatment is likely to be useful. Preclinical studies take place before any testing in humans is done.

In medicine, action taken to decrease the chance of getting a disease or condition. For example, cancer prevention includes avoiding risk factors (such as smoking, obesity, lack of exercise, and radiation exposure) and increasing protective factors (such as getting regular physical activity, staying at a healthy weight, and having a healthy diet).

An aggressive (fast-growing) type of acute myeloid leukemia in which there are too many immature blood-forming cells in the blood and bone marrow. It is usually marked by an exchange of parts of chromosomes 15 and 17. Also called acute promyelocytic leukemia and APL.

Cancer that forms in tissues of the prostate (a gland in the male reproductive system found below the bladder and in front of the rectum). Prostate cancer usually occurs in older men.

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

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

The part of the digestive tract that is located between the stomach and the large intestine.

An organ that is part of the digestive system. The stomach helps digest food by mixing it with digestive juices and churning it into a thin liquid.

Adding nutrients to the diet.

An indication that a person has a condition or disease. Some examples of symptoms are headache, fever, fatigue, nausea, vomiting, and pain.

Treatment.

A group or layer of cells that work together to perform a specific function.

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

A poison produced by certain animals, plants, or bacteria.

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.