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Milk Thistle (silybum marianum)

What is milk thistle? What is it used for?

Originally from the Mediterranean, milk thistle is now found throughout the world, especially the eastern United States and California. The plant can grow as tall as 10 feet, with broad, wavy leaves; red-purple flowers; and brown, shiny fruit.

Milk thistle products are made from the seeds inside the fruit. These seeds contain a bioflavonoid complex known as silymarin, which provide most of the plant's medical benefits. Silymarin is made up of three parts: silibinin, silidianin, and silicristin. Silibinin is the most active part and is largely responsible for the benefits attributed to silymarin. The use of milk thistle can be traced back more than 2,000 years, where it was used by early physicians as a remedy for snakebites and jaundice. It was also used by nursing mothers to promote the production of milk.

Placebo-controlled, double blind studies have shown milk thistle extracts to be effective in patients with cirrhosis of the liver, chronic hepatitis and some types of diabetes. Milk thistle also alters bile makeup, which can potentially reduce the risk of gallstones. Other conditions that can be helped by milk thistle include psoriasis, eczema, skin burns, wounds and sores.

How much milk thistle should I take?

Although a recommended daily allowance has yet to be determined, many health experts recommended a dosage of 1-4 grams of dried fruit (seeds) per day; patients can also take a protective dose of 120 mg of silymarin daily. For liver disease and impaired liver function, some doctors of natural medicine suggest 420 mg of silymarin per day from an herbal extract of milk thistle standardized to 70-80% silymarin content. Improvement should be noted between 8-12 weeks; once that occurs, intake may be reduced to 280 mg of silymarin per day for preventive measures.

What forms of milk thistle are available?

Dried milk thistle is readily available in capsule form. Extracts and tinctures of milk thistle can also be found at most health stores. In addition, milk thistle seeds can be ground and eaten or made into a tea.

What can happen if I take too much milk thistle? Are there any interactions I should be aware of? What precautions should I take?

No toxicity has been reported with milk thistle. However, because it can cause increased bile flow and secretion, milk thistle may have a mild laxative effect. In those instances, dietary fiber (in the form of guar gum, psyllium, oat bran or pectin) can be taken to stop loose stools or stomach discomfort.

Certain medications may react with milk thistle, including acetaminophen, lovastatin, general anesthetics, and some chemotherapy medications. Patients taking these types of drugs should consult with their doctor before taking milk thistle or milk thistle products. As always, make sure to consult with a licensed health care provider before taking milk thistle or any other herbal remedy or dietary supplement.


  • Allain H, SchuNck S, Lebreton S, et al. Aminotransferase levels and silymarin in de novo tacrine-treated patients with Alzheimer's disease. Dementia Geriatr Cogn Disorders 1999;10:181|5.
  • Brown DJ. Herbal Prescriptions for Better Health. Rocklin, CA: Prima Publishing, 1996, 151-58.
  • Katiyar SK. Silymarin and skin cancer prevention: anti-inflammatory, antioxidant and immunomodulatory effects. Int J Oncol Jan 2005;26(1):169-76.
  • Pares A, Plancs R, Torres M, et al. Effects of silymarin in alcoholic patients with cirrhosis of the liver: results of a controlled, double-blind, randomized and multicenter trial. J Hepatol 1998;28:615-21.
  • Velussi M, Cernogoi AM, De Monte A, et al. Long-term (12 months) treatment with an antioxidant drug (silymarin) is effective on hyperinsulinemia, exogenous insulin need and malondialdehyde levels in cirrhotic diabetic patients. J Hepatology 1997;26:871|9.
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