Milk Thistle

October 2, 2008

SCIENTIFIC NAMES: Silybum marianum, Carduus marianum

ABSTRACT: Integrative Oncology is the synthesis of mainstream care and nonpharmacologic, evidence-based complementary therapies for the control of cancer-related physical and emotional symptoms. Herb-drug interactions and other cautions are also encompassed. This month, we review the plant milk thistle, which has been used medicinally for thousands of years, primarily for diseases of the liver.

SCIENTIFIC NAMES: Silybum marianum, Carduus marianum

ALSO KNOWN AS: Holy thistle, lady’s thistle, Mary thistle, Marian thistle, St. Mary’s thistle

USES: Milk thistle is used to treat alcoholism, hepatitis, drug-induced hepatotoxicity, liver disease, cirrhosis, and food poisoning, as well as to prevent cancer. Milk thistle can be ingested as a tea, or as capsules, extracts, or tinctures.

BACKGROUND: Milk thistle is an annual plant native to the Mediterranean regions of Europe, North Africa, and Middle East.

RESEARCH: Silymarin, a flavolignan derived from the seed, pod, or fruit of the plant milk thistle, has proved effective against liver cirrhosis in placebo-controlled studies.[1] Clarification of its benefit against alcoholic liver disease and hepatitis B or C viral liver disease awaits additional research.[2] Supplementation with milk thistle has also improved glycemic profiles in type II diabetic patients.[3] In addition, Silymarin has exhibited chemopreventive properties both in vivo and in vitro, which may be produced via anti-inflammatory, apoptosis-inducing, cell cycle–modulating, antiangiogenic, or antimetastatic mechanisms.[4,5] Investigations in humans have not yet been conducted.

ADVERSE EFFECTS: Common: Diarrhea caused by mild laxative effect; uterine and menstrual stimulation. Case report: Intermittent episodes of sweating, nausea, vomiting, diarrhea, abdominal pain, weakness, and collapse were reported in one patient, but these symptoms resolved after discontinuation of milk thistle.[6]

DR. CASSILETH: Cancer patients must understand that herbal supplements are not viable substitutes for mainstream cancer care. Moreover, the potential for herb-drug interactions that may reduce efficacy of chemotherapeutic agents is a serious concern. Used primarily for liver diseases, milk thistle demonstrated anticancer potential in both in vitro and in vivo studies. However, human studies have not been conducted. Despite the lack of human data, many websites promote milk thistle to cancer patients. Caution is needed as there is no evidence of safety or effi cacy. Because reliable information about herbs and other dietary supplements was not readily available to oncologists who need it to counsel their patients, the MSKCC Integrative Medicine Service developed and maintains a free website called “AboutHerbs” (http://www.mskcc. org/AboutHerbs). This site contains two portals, one for oncology professionals and another for the public. Anyone may enter either portal at no cost. This continually updated site provides objective information about herbs and other botanicals, vitamins, other dietary supplements and unproved cancer therapies. Each of 230 (and growing) entries includes a clinical summary and details about constituents, interactions, benefi ts, and adverse effects.

-Barrie Cassileth



1. Saller R, Brignoli R, Melzer J, et al: An updated systematic review with meta-analysis for the clinical evidence of silymarin. Forsch Komplementmed 15:9-20, 2008.

2. Rambaldi A, Jacobs BP, Gluud C: Milk thistle for alcoholic and/or hepatitis B or C virus liver diseases. Cochrane Database Syst Rev (4):CD003620, 2007.

3. Huseini HF, Larijani B, Heshmat R, et al: The efficacy of Silybum marianum (L.) Gaertn. (silymarin) in the treatment of type II diabetes: A randomized, double-blind, placebo-controlled, clinical trial. Phytother Res 20:1036-1039, 2006.

4. Ramasamy K, Agarwal R: Multitargeted therapy of cancer by silymarin. Cancer Lett May 8, 2008 (epub ahead of print).

5. Kohno H, Tanaka T, Kawabata K, et al: Silymarin, a naturally occurring polyphenolic antioxidant flavonoid, inhibits azoxymethane-induced colon carcinogenesis in male F344 rats. Int J Cancer 101:461-468, 2002.

6. Adverse Drug Reactions Advisory Committee: An adverse reaction to the herbal medication milk thistle (Silybum marianum). Med J Aust 170:218-219, 1999.

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