Milk thistle – Know What Herbs Do What

Latin Name – Silybum marianum

Milk thistle - Know What Herbs Do What

Botanical Illustration of Silybum marianum from Flora von Deutschland Österreich und der Schweiz 1885

Milk thistle is a flowering herb that is native to the Mediterranean region. It has been used for thousands of years as an herbal remedy for a variety of ailments, especially liver problems.  Silymarin, which can be extracted from the seeds (fruit) of the milk thistle plant, is believed to be the biologically active part of the herb. The seeds are used to prepare capsules, extracts, and infusions (strong teas).


A traditional view of milk thistle is as an herbal remedy to help protect the liver and improve its function.


Milk thistle has been used as a nutritional supplement in the hope of improving  liver cirrhosis, chronic hepatitis (liver inflammation), and gallbladder disorders.


There have been some research studies of milk thistle on liver disease in humans, but these have been small. Some promising data have been reported, but study results at this time are mixed.


Although some studies conducted outside the United States support claims of oral milk thistle to improve liver function, there have been flaws in study design and reporting. To date, there is no conclusive evidence to prove its claimed uses.


Recent NCCAM-funded research includes a phase II study to better understand the use of milk thistle for chronic hepatitis C. Additional research, cofunded by NCCAM and the National Institute of Diabetes and Digestive and Kidney Diseases, includes studies of milk thistle for chronic hepatitis C and nonalcoholic steatohepatitis, or NASH, a fatty, inflamed liver disease that occurs in people who drink little or no alcohol.


Side Effects and Cautions Summary

Milk thistle - Know What Herbs Do What


  • Milk thistle side effects include a laxative effect, upset stomach, diarrhea, and bloating.
  • Milk thistle can produce allergic reactions, which tend to be more common among people who are allergic to plants in the same family (for example, ragweed, chrysanthemum, marigold, and daisy).
  • Tell your health care providers about any complementary and alternative practices you use. Give them a full picture of what you do to manage your health to help ensure coordinated and safe care.  Complementary or alternative therapy should not be used in place of conventional medical care or to delay seeking that care.




  • Agency for Healthcare Research and Quality. Milk Thistle: Effects on Liver Disease and Cirrhosis and Clinical Adverse Effects. Evidence Report/Technology Assessment no. 21. Rockville, MD: Agency for Healthcare Research and Quality; 2000. 01-E024.
  • Milk thistle (Silybum marianum). In: Coates P, Blackman M, Cragg G, et al., eds. Encyclopedia of Dietary Supplements. New York, NY: Marcel Dekker; 2005:467–482.
  • Milk thistle. Natural Medicines Comprehensive Database. Accessed on July 3, 2007.
  • Milk thistle (Silybum marianum), silymarin. Natural Standard Database Web site. Accessed on June 28, 2007.
  • Milk thistle fruit. In: Blumenthal M, Goldberg A, Brinckman J, eds. Herbal Medicine: Expanded Commission E Monographs. Newton, MA: Lippincott Williams & Wilkins; 2000:257–263.
  • National Center for Complementary and Alternative Medicine. Hepatitis C and Complementary and Alternative Medicine: 2003 Update. National Center for Complementary and Alternative Medicine Web site. Accessed on July 5, 2007.


For More Information


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


The NCCAM Clearinghouse provides information on CAM and NCCAM, including publications and searches of Federal databases of scientific and medical literature. The Clearinghouse does not provide medical advice, treatment recommendations, or referrals to practitioners.

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Source: National Center for Complementary and Alternative Medicine, Milk thistle fact sheet Created September 2005, Updated March 2008


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