Milk thistle (Silybum marianum) has been used for 2,000 years as an herbal remedy for a variety of ailments, particularly liver, kidney, and gall bladder problems. Several scientific studies suggest that substances in milk thistle (especially a flavonoid called silymarin) protect the liver from toxins, including certain drugs such as acetaminophen (Tylenol), which can cause liver damage in high doses. Silymarin has antioxidant and anti-inflammatory properties, and it may help the liver repair itself by growing new cells.
Although a number of animal studies demonstrate that milk thistle can be helpful in protecting the liver, results in human studies are mixed.
Liver disease from alcohol
Milk thistle is often suggested as a treatment for alcoholic hepatitis and alcoholic cirrhosis. But scientific studies show mixed results. Most studies show milk thistle improves liver function and increases survival in people with cirrhosis or chronic hepatitis. But problems in the design of the studies (such as small numbers of participants and differences in dosing and duration of milk thistle therapy) make it hard to draw any real conclusions.
Milk thistle is widely used in the treatment of viral hepatitis (particularly hepatitis C). However, studies show mixed results. Some found improvements in liver function, while others did not. In one study of 16 patients who didn't respond to interferon and ribavirin therapy, milk thistle significantly reduced the viral load of hepatitis C. In 7 of the subjects the virus decreased to undetectable levels after 14 days of therapy.
Based on traditional use, milk thistle has been used as an emergency antidote to poisoning by deathcap mushroom (Amanita phalloides). Animal studies have found that milk thistle extract completely counteracts the toxic effects of the mushroom when given within 10 minutes of ingestion. If given within 24 hours, it significantly reduces the risk of liver damage and death.
Early laboratory studies also suggest that silymarin and other active substances in milk thistle may have anticancer effects. These substances appear to stop cancer cells from dividing and reproducing, shorten their lifespan, and reduce blood supply to tumors. Some studies suggest silymarin may favorably supplement sunscreen protection and may help reduce the risk of skin cancer. More studies are needed, however, to show whether milk thistle has any effects in the body (not just in test tubes).
The use of herbs is a time honored approach to strengthening the body and treating disease. Herbs, however, can trigger side effects and can interact with other herbs, supplements, or medications. For these reasons, you should take herbs with care, under the supervision of a health care practitioner.
Milk thistle is generally regarded as safe. Side effects are usually mild and may involve stomach upset and diarrhea. Some people may get a rash from touching milk thistle plants.
Milk thistle should not be used by pregnant or breastfeeding women.
People with a history of hormone related cancers, including breast, uterine, and prostate cancer, should not take milk thistle.
Do not take milk thistle if you are allergic to ragweed, chrysanthemums, marigolds, chamomile, yarrow, or daisies.
Agarwal R, Agarwal C, Ichikawa H, Singh RP, Aggarwal BB. Anticancer potential of silymarin: from bench to bed side. Anticancer Res. 2006 Nov-Dec;26(6B):4457-98. Review.
Agency for Healthcare Research and Quality. Milk thistle: effects on liver disease and cirrhosis and clinical adverse effects. Summary, evidence report/technology assessment: number 21, September 2000.
Asghar Z, Masood Z. Evaluation of antioxidant properties of silymarin and its potential to inhibit peroxyl radicals in vitro. Pak J Pharm Sci. 2008 Jul;21(3):249-54.
Barve A, Khan R, Marsano L, Ravindra KV, McClain C. Treatment of alcoholic liver disease. Ann Hepatol. 2008 Jan-Mar;7(1):5-15. Review.
Blumenthal M, Goldberg A, Brinckmann J. Herbal Medicine: Expanded Commission E Monographs. Newton, MA: Integrative Medicine Communications; 2000:257-263.
Brantley SJ, Oberlies NH, Kroll DJ, Paine MF. Two flavonolignans from milk thistle (silybum marianum) inhibit CYP2C9-mediated warfarin metabolism at clinically achievable concentrations. J Pharmacol Exp Ther. 2010;332(3):1081-7.
Ferenci P, Scherzer TM, Kerschner H, Rutter K, Beinhardt S, Hofer H, et al. Silibinin is a potent antiviral agent in patients with chronic hepatitis C not responding to pegylated interferon/ribavirin therapy. Gastroenterology. 2008 Nov;135(5):1561-7.
Gazak R, Walterova D, Kren V. Silybin and silymarin -- new and emerging applications in medicine. Curr Med Chem. 2007;14(3):315-38. Review.
Giese LA. A study of alternative health care use for gastrointestinal disorders. Gastroenterol Nurs. 2000;23(1):19-27.
Gordon A, Hobbs DA, Bowden DS, Bailey MJ, Mitchell J, Francis AJ, Roberts SK. Effects of Silybum marianum on serum hepatitis C virus RNA, alanine aminotransferase levels and well-being in patients with chronic hepatitis C. J Gastroenterol Hepatol. 2006 Jan;21(1 Pt 2):275-80.
Hoh C, Boocock D, Marczylo T, Singh R, Berry DP, Dennison AR, et al. Pilot study of oral silibinin, a putative chemopreventive agent, in colorectal cancer patients: silibinin levels in plasma, colorectum, and liver and their pharmacodynamic consequences. Clin Cancer Res. 2006 May 1;12(9):2944-50.
Jiang C, Agarwal R, Lu J. Anti-angiogenic potential of a cancer chemopreventive flavonoid antioxidant, Silymairn: inhibition of key attributes of vascular endothelial cells and angiogenic cytokine secretion by cancer epithelial cells. Biochem Biophys Res Commun. 2000;276:371-378.
Köksal E, Gülçin I, Beyza S, Sarikaya O, Bursal E. In vitro antioxidant activity of silymarin. J Enzyme Inhib Med Chem. 2009 Apr;24(2):395-405.
Low Dog T. Traditional and alternative therapies for breast cancer. Altern Ther Health Med. 2001;7(3):36-47.
Mandell: Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, 7th ed. Philadelphia, PA. Churchill Livingstone, 2009.
Mayer KE, Myers RP, Lee SS. Silymarin treatment of viral hepatitis: a systematic review. J Viral Hepat. 2005 Nov;12(6):559-67. Review.
Michelfelder A, Lee K, Bading E. Integrative Medicine and Gastrointestinal Disease. 2009.
Najm W, Lie D. Dietary supplements commonly used for prevention. Prim Care. 2008 Dec;35(4):749-67.
Rainone F. Milk thistle. Am Fam Physician. 2005 Oct 1;72(7):1285-8. Review.
Ramasamy K, Agarwal R. Multitargeted therapy of cancer by silymarin. Cancer Lett. 2008 Oct 8;269(2):352-62. Review.
Rambaldi A, Jacobs BP, Iaquinto G, Gluud C. Milk thistle for alcoholic and/or hepatitis B or C liver diseases -- a systematic cochrane hepato-biliary group review with meta-analyses of randomized clinical trials. Am J Gastroenterol. 2005 Nov;100(11):2583-91. Review.
Rotblatt M, Ziment I. Evidence-Based Herbal Medicine. Philadelphia, PA: Hanley & Belfus, Inc; 2002:266-271.
Saller R, Brignoli R, Melzer J, Meier R. An updated systematic review with meta-analysis for the clinical evidence of silymarin. Forsch Komplementmed. 2008 Feb;15(1):9-20. Review.
Vaid M, Katiyar SK. Molecular mechanisms of inhibition of photocarcinogenesis by silymarin, a phytochemical from milk thistle (Silybum marianum L. Gaertn.) (Review). Int J Oncol. 2010;36(5):1053-60.
Wu JW, Lin LC, Tsai TH. Drug-drug interactions of silymarin on the perspective of pharmacokinetics. J Ehtnopharmacol. 2009;121(2):185-93.
Zielinska-Przyjemska M, Wiktorowicz K. An in vitro study of the protective effect of the flavonoid silydianin against reactive oxygen species. Phytother Res. 2006 Feb;20(2):115-9