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Milk Thistle

Botanical name(s):

Silybum marianum

Other name(s):

milk thistle, marian thistle, Mary thistle, silibinin, silicristin, silidianin, silmar, silybin, silybum, silymarin,

General description

Milk thistle is an annual or biennial plant with reddish-purple flowers that grows up to three feet tall. Sometimes considered a weed, it is native to Europe and grows in dry, rocky soils. Milk thistle seeds (now known as Silybum marianum) have been used for hundreds of years to treat liver and gallbladder disease.

Photo of milk thistle

Milk thistle contains a group of bioflavonoids, collectively referred to as silymarin, produced from the seeds of the thistle. The most active of the group has been identified as silybin. Silymarin is claimed to protect the liver from damage by preventing toxins from attaching to the liver cells and by neutralizing free radicals. It has been used in the treatment of toxic-mushroom poisoning, cirrhosis, and hepatitis.

Medically valid uses

Within the last 30 years, silybin, the extract of milk thistle seeds, has been used by the medical community as a hepatoprotectant (protecting the liver) to treat various liver conditions, including mushroom poisoning, viral hepatitis, cirrhosis, alcoholic liver disease, and carbon tetrachloride poisoning.

Milk thistle has been studied in the laboratory for its ability to protect liver cells from inflammation, with mixed results.

A large study investigating the use of milk thistle for hepatitis C found that patients had fewer symptoms and better quality of life, although there was no change in the level of virus activity or liver inflammation. 

A few preliminary studies have suggested that taking the milk thistle constituent silymarin 200 mg three times daily for four months, in combination with conventional treatment, appears to significantly decrease fasting blood glucose, hemoglobin A1C (HbA1C), total cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides compared to placebo in patients with type 2 diabetes.   

Unsubstantiated claims

Please note that this section reports on claims that have NOT yet been substantiated through scientific studies.

Research is evaluating the effectiveness of milk thistle in protecting the kidneys and pancreas against the effects of chemotherapy and in protecting against breast cancer.

Dosing format

For standardized preparations of milk thistle, follow the packaging instructions for the correct dose.

Side effects, toxicity, and interactions

Milk thistle can produce allergic reactions, especially in people who are allergic to ragweed and other plants in the same family.

Milk thistle may lower blood sugar levels, so should be used with caution by people with diabetes or hypoglycemia, and people taking drugs or supplements that affect blood sugar levels. 

Women who are pregnant or breastfeeding should consult a physician before taking any herbal supplements.

Additional information

Click here for a list of reputable websites with general information on nutrition.

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