Milk Thistle Monograph

A milk thistle monograph for the home

This milk thistle monograph provides basic information about milk thistle—common names, usefulness and safety, and resources for more information.

Milk thistle is native to southern Europe, southern Russia, Asia Minor, and northern Africa. It also grows in North and South America and South Australia.
Silymarin is considered to be the main component of milk thistle seeds, but the terms “milk thistle” and “silymarin” often are used interchangeably.
Historically, people have used milk thistle for liver disorders, such as hepatitis and cirrhosis, and gallbladder problems.
Silymarin is the most commonly used herbal supplement in the United States for liver problems.
Milk thistle products are available as capsules, powders, and extracts.

We know little about whether milk thistle is effective in people, as only a few well-designed clinical studies have been conducted.

Results from clinical trials of milk thistle for liver diseases have been mixed, and two rigorously designed studies found no benefit.
The 2008 Hepatitis C Antiviral Long-Term Treatment Against Cirrhosis (HALT-C) study, sponsored by the National Institutes of Health (NIH), found that hepatitis C patients who used silymarin had fewer and milder symptoms of liver disease and somewhat better quality of life but no change in virus activity or liver inflammation.
A 2012 clinical trial, cofunded by the National Center for Complementary and Integrative Health (NCCIH) and the National Institute of Diabetes and Digestive and Kidney Diseases, showed that two higher-than-usual doses of silymarin were no better than placebo for chronic hepatitis C in people who had not responded to standard antiviral treatment.
Results from a 2013 clinical study suggest that milk thistle may enhance standard treatment in young people with a particular form of anemia (Cooley’s anemia).

In clinical trials, milk thistle appears to be well tolerated in recommended doses. Occasionally, people report various gastrointestinal side effects.
Milk thistle may 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).
Compounds in milk thistle may lower blood sugar levels in people with type 2 diabetes. People with diabetes should use caution.

Abenavoli L, Capasso R, Milic N, et al. Milk thistle in liver diseases: past, present, future. Phytotherapy Research. 2010;24(10):1423-1432.
Fried MW, Navarro VJ, Afdhal N, et al. Effect of silymarin (milk thistle) on liver disease in patients with chronic hepatitis C unsuccessfully treated with interferon therapy: a randomized, controlled trial. JAMA. 2012;308(3):274-282.
Loguercio C, Festi D. Silybin and the liver: from basic research to clinical practice.World Journal of Gastroenterology. 2011;17(18):2288-2301.
Milk Thistle. Natural Medicines Web site. Accessed at naturalmedicines.therapeuticresearch.com on April 8, 2015. [Database subscription].
Moayedi B, Gharagozloo M, Esmaeil N, et al. A randomized double-blind, placebo-controlled study of therapeutic effects of silymarin in ß-thalassemia major patients receiving desferrioxamine.European Journal of Haematology. 2013;90(3):202-209.
Polyak SJ, Oberlies NH, Pécheur E-I, et al. Silymarin for HCV infection. Antiviral Therapy. 2013;18(2):141-147.
Seeff LB, Curto TM, Szabo G, et al. Herbal product use by persons enrolled in the Hepatitis C Antiviral Long-Term Treatment Against Cirrhosis (HALT-C) trial.Hepatology. 2008;47(2):605-612.