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Other common
name(s): Mary thistle, Marian thistle, holy thistle, lady
thistle, silymarin
Scientific/medical
name(s): Silybum
marianum
Description
Milk thistle, a plant belonging to the same family as daisies,
is native to the Mediterranean regions and grows in Europe, North
America, South America, and Australia. The ripe seeds are used to make
herbal remedies. They contain the antioxidant silymarin, which is
thought to be responsible for milk thistle's helpful effects. Silymarin
is a combination of 3 different compounds: silybinin (also called
silybin or silibinin), silidyanin (also spelled silidianin), and
silychristin (also spelled silichristin).
Overview
A few studies have suggested that silymarin, an antioxidant,
may be useful for treating certain types of liver diseases in humans
such as cirrhosis or chronic hepatitis. Most of the studies did not
show improved survival, although laboratory tests showed an improvement
in liver function in some. Larger randomized clinical trials are needed
to determine whether these effects are reliable. Early studies in test
tubes and laboratory animals have suggested that silymarin may help
with cancer prevention and treatment. Human studies are needed to find
out what role silymarin may play in preventing or treating cancer in
people.
How is it promoted for use?
Proponents claim that milk thistle detoxifies and protects the
liver and is an effective treatment for hepatitis C, jaundice, and
cirrhosis. They also claim it strengthens the spleen and gallbladder,
benefits people with diabetes, and slows the growth of certain types of
cancer, including skin cancer, breast cancer, and prostate cancer. Some
believe that milk thistle is an antidote for certain varieties of
poisonous mushrooms.
Proponents also state that silymarin is a potent antioxidant.
Antioxidants are compounds that block the action of activated oxygen
molecules called free radicals, which can damage cells.
What does it involve?
Milk thistle supplements are made from the ripe seed, which is
actually the fruit of the plant. The supplement is available as a
capsule, tablet, powder, and liquid extract. Powdered milk thistle can
be made into a tea. A typical daily dose ranges from 140 to 400
milligrams of silymarin, usually divided into 2 or 3 doses. The leaves,
flower, roots, and stalk of the milk thistle plant contain very little
silymarin and are usually not used in supplements.
What is the history behind it?
Milk thistle has been used for thousands of years in Europe as
a liver restorative. It was recommended to treat malaria, melancholy,
plague, and many other illnesses. It was also thought to reduce the
effects of toxins such as poisonous mushrooms and alcohol on the liver.
All parts of the milk thistle plant have been eaten as food in European
countries, and its seeds have been made into a drink similar to coffee.
Only recently have scientists begun to test its effectiveness in
treating illness.
What is the evidence?
Silymarin has been studied extensively in the laboratory for
the treatment of short-term and chronic liver diseases, and to a lesser
extent for some types of cancer. Some research indicates that silymarin
may be useful for treating certain liver diseases, particularly those
caused by exposure to toxins. Commission E (Germany's regulatory agency
for herbs) approved the use of milk thistle fruit (the part of the
plant that contains silymarin) as a treatment for toxic liver disease
and a supportive treatment for chronic inflammatory liver disease and
cirrhosis of the liver.
One review of both clinical and laboratory research found that
silymarin may be effective for patients with hepatitis, alcoholic liver
disease, and cirrhosis. However, the researchers noted that all of the
clinical trials were conducted outside of the United States, were
difficult to interpret, involved small numbers of patients, and were
not consistent in following scientific methods.
More recently, a group reviewed studies of the use of milk
thistle for alcoholic or viral hepatitis and observed problems with
study methods in most of them. For example, fewer than half of the
studies were properly double-blinded, meaning participants or
researchers might have been aware of which substance was being tested.
In the clinical trials that were properly conducted, milk thistle did
not show any effect.
Studies in laboratory mice have concluded that silymarin
provided some protection against skin cancer caused by chemical
carcinogens or ultraviolet radiation, possibly because of its
antioxidant properties. Studies using cancer cells grown in a
laboratory and mouse studies found that silymarin reduced growth of
breast, prostate, and cervical cancer cells. These test tube studies
also suggested that silymarin may be able to enhance the effectiveness
of some chemotherapy drugs. Further studies are required to find out
whether the results apply to humans. Preliminary clinical studies in
cancer patients indicate that silymarin does not cause serious side
effects. However, studies of anti-cancer activity in human patients
have not been published as of 2008.
A study of rats given a type of chemotherapy that often harms
the kidneys showed less kidney damage in rats that were also given
simylarin. Again, human studies are needed to learn whether this effect
might also happen in people.
Are there any possible problems or
complications?
This product is sold as a
dietary supplement in the United States. Unlike companies that produce
drugs (which must provide the FDA with results of detailed testing
showing their product is safe and effective before the drug is approved
for sale), the companies that make supplements do not have to show
evidence of safety or health benefits to the FDA before selling their
products. Supplement products without any reliable scientific evidence
of health benefits may still be sold as long as the companies selling
them do not claim the supplements can prevent, treat, or cure any
specific disease. Some such products may not contain the amount of the
herb or substance that is written on the label, and some may include
other substances (contaminants). Though the FDA has written new rules
to improve the quality of manufacturing processes for dietary
supplements and the accurate listing of supplement ingredients, these
rules do not take full effect until 2010. And, the new rules do not
address the safety of supplement ingredients or their effects on health
when proper manufacturing techniques are used.
Most such
supplements have not been tested to find out if they interact with
medicines, foods, or other herbs and supplements. Even though some
reports of interactions and harmful effects may be published, full
studies of interactions and effects are not often available. Because of
these limitations, any information on ill effects and interactions
below should be considered incomplete.
Silymarin is generally considered safe. A few people have
reported stomach upset such as nausea, abdominal pain, diarrhea, and
vomiting, although this is thought to have been due to contamination of
the supplement with outside substances, not the silymarin itself. Large
doses of silymarin may have a laxative effect. Allergic reactions are
rare, but may be more common among people who are allergic to plants in
the same family, such as ragweed, chrysanthemums, marigolds, and
daisies. Anyone who has hives, shortness of breath, dizziness, or
swelling in the mouth or throat after taking silymarin should call
emergency services right away. Studies have not been done to test
silymarin's safety in children or in pregnant or breast-feeding women.
In general, antioxidant supplements are not recommended during
chemotherapy or radiation therapy for cancer, since they can block some
of the cancer-killing effects of these treatments.
In addition, the potential interactions between silymarin and
other drugs and herbs should be considered. Some of these combinations
may be dangerous. Always tell your doctor and pharmacist about any
herbs you are taking. Relying on this type of treatment alone and
avoiding or delaying conventional medical care for cancer may have
serious health consequences.
Additional Resources
More information from your American Cancer
Society
The following information on complementary and alternative
therapies may also be helpful to you. These materials may be found on
our Web site (www.cancer.org)
or ordered from our toll-free number (1-800-ACS-2345).
References
Agency for Healthcare Research and Quality. Milk thistle:
effects on liver disease and cirrhosis and clinical adverse effects.
AHRQ Evidence Reports, Numbers 1-60 National Center for
Biotechnology Information Web site.
http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=hstat1.section.29172.
Accessed June 6, 2008.
Blumenthal M, ed. The Complete German Commission E Monographs:
Therapeutic Guide to Herbal Medicines. Austin, TX: American Botanical
Council; 1998.
Crops: milk thistle. Manitoba Agriculture, Food and Rural
Initiatives Web site.
http://www.gov.mb.ca/agriculture/crops/medicinal/bkq00s15.html. Updated
March 2006. Accessed June 6, 2008.
Fetrow CW, Avila JR. Professional's
Handbook of Complementary & Alternative Medicines.
Springhouse, PA: Springhouse Corp; 1999.
Flora K, Hahn M, Rosen H, Benner K. Milk thistle (Silybum
marianum) for the therapy of liver disease. Am J Gastroenterol.
1998;93:139-143.
Gruenwald J. PDR
for Herbal Medicines. 3rd ed. Montvale, NJ: Thomson PDR;
2004.
Langenfeld J. Milk thistle. Creighton University School of
Medicine Complementary and Alternative Medicine Web site.
http://altmed.creighton.edu/MilkThistle/. Accessed June 6, 2008.
Lawenda BD, Kelly KM, Ladas EJ, Sagar SM, Vickers A, Blumberg
JB. Should supplemental antioxidant administration be avoided during
chemotherapy and radiation therapy? J Natl Cancer Inst.
2008;100:773-783.
Milk thistle. Memorial Sloan-Kettering Cancer Center Web site.
http://www.mskcc.org/mskcc/html/69303.cfm. Updated August 7, 2007.
Accessed June 6, 2008.
Milk thistle. National Cancer Institute Web site.
http://www.cancer.gov/cancertopics/pdq/cam/milkthistle/HealthProfessional/page1.
Updated March 20, 2008. Accessed July 31, 2008.
National Center for Complementary and Alternative Medicine,
National Institutes of Health. Milk thistle. National Center for
Complementary and Alternative Medicine Web site.
http://nccam.nih.gov/health/milkthistle/milkthistle.pdf. Created
September 2005. Accessed June 6, 2008.
Rambaldi A, Jacobs BP, Iaquinto G, Gluud C. Milk thistle for
alcoholic and/or hepatitis B or C virus liver diseases. Cochrane Database Syst Rev.
2005;(2):CD003620.
Singh RP, Agarwal R. Mechanisms and preclinical efficacy of
silibinin in preventing skin cancer. Eur J Cancer.
2005;41:1969-1979.
Singh RP, Deep G, Chittezhath M, Kaur M, Dwyer-Nield LD,
Malkinson AM, Agarwal R. Effect of silibinin on the growth and
progression of primary lung tumors in mice. J Natl Cancer Inst.
2006;98:846-855.
Singh RP, Mallikarjuna GU, Sharma G, Dhanalakshmi S, Tyagi AK,
Chan DC, Agarwal C, Agarwal R. Oral silibinin inhibits lung tumor
growth in athymic nude mice and forms a novel chemocombination with
doxorubicin targeting nuclear factor kappaB-mediated inducible
chemoresistance. Clin
Cancer Res. 2004;10:8641-8647.
Tyagi AK, Agarwal C, Chan DC, Agarwal R. Synergistic
anti-cancer effects of silibinin with conventional cytotoxic agents
doxorubicin, cisplatin and carboplatin against human breast carcinoma
MCF-7 and MDA-MB468 cells. Oncol
Rep. 2004;11:493-499.
van Erp NP, Baker SD, Zhao M, Rudek MA, Guchelaar HJ, Nortier
JW, Sparreboom A, Gelderblom H. Effect of milk thistle (Silybum
marianum) on the pharmacokinetics of irinotecan. Clin Cancer Res.
2005;11:7800-7806.
Zi X, Grasso AW, Kung HJ, Agarwal R.. A flavonoid antioxidant,
silymarin, inhibits activation of erbB1 signaling and induces
cyclin-dependent kinase inhibitors, G1 arrest, and anticarciniogenic
effects in human prostate carcinoma DU145 cells. Cancer Res.
1999;59:622-632.
Note: This information may not cover
all possible claims, uses, actions, precautions, side effects or
interactions. It is not intended as medical advice, and should not be
relied upon as a substitute for consultation with your doctor, who is
familiar with your medical situation.
Last Medical Review: 11/01/2008
Last Revised: 11/01/2008
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