Health Library

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. It has reddish-purple flowers. It grows to three feet tall. It’s often considered a weed. It comes from Europe. It grows in dry, rocky soils. Milk thistle seeds (Silybum marianum) have been used for hundreds of years to treat liver and gallbladder disease.

Milk thistle contains a group of bioflavonoids. These are called silymarin. They’re made from the seeds of the thistle. The most active of the group is silybin. These may protect the liver from damage. It works by stopping toxins from attaching to the liver cells. It also neutralizes free radicals. It’s been used to treat toxic-mushroom poisoning, cirrhosis, and hepatitis.

Medically valid uses

Within the last 30 years, silybin has been used to protect the liver. It treats liver issues. These include including mushroom poisoning, viral hepatitis, and cirrhosis. They also include alcoholic liver disease and carbon tetrachloride poisoning.

Milk thistle has been studied to check if it protects liver cells from inflammation. However, results are mixed.

A large study looked at the use of milk thistle for hepatitis C. It found that people had fewer symptoms and better quality of life. But there was no change in the level of virus activity or liver inflammation. 

A few early studies suggest that taking 200 mg of silymarin three times per day for four months with conventional treatment may have health benefits in people with type 2 diabetes. These include decreasing fasting blood glucose, hemoglobin A1C (HbA1C), total cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides.

Unsubstantiated claims

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

Milk thistle may protect the kidneys and pancreas against the effects of chemotherapy. It may also protect against breast cancer. Studies are ongoing.

Dosing format

Follow the instructions on the package for the correct dose.

Side effects, toxicity, and interactions

Milk thistle can cause allergic reactions. Your risk may be higher if you’re allergic to ragweed and other plants in the same family.

Milk thistle may lower blood sugar levels. If you have diabetes or low blood sugar (hypoglycemia), talk to your healthcare provider before using it. You should also talk to your healthcare provider if you take medicines or supplements that affect blood sugar levels.

Women who are pregnant or breastfeeding should talk to their healthcare providers before taking any supplements.

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