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Milk Thistle

Health benefits, Uses, Side Effects & More


Updated May 23, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Milk thistle
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Milk thistle is a plant native to Europe. It has a long history of use as a folk remedy for liver and gallbladder disorders. The active constituent of milk thistle is thought to be silymarin, a flavonoid found in the seeds.

Other names for it include silymarin, Marian Thistle, Mediterranean Thistle, Mary Thistle, Holy Thistle, and Silybum Marianum.

Health Benefits of Milk Thistle:

1) Hepatitis

Milk thistle supplements have been explored for chronic hepatitis, however, larger, well-designed studies are needed before it can be recommended for this condition.

Related: Natural Remedies for Hepatitis C

2) Cirrhosis

Preliminary studies suggest milk thistle supplements may be beneficial for people with cirrhosis. It may improve liver function. More research is needed, however, because many of the studies conducted so far on milk thistle and cirrhosis have been poorly designed.

Related: Herbs for the Liver

3) Protection From Liver Damage

Milk thistle may protect the liver against toxicity from acetaminophen (Tylenol), alcohol and other drugs. In Europe, milk thistle is reportedly administered to patients when they are given medications known to cause liver problems.

4) Other Conditions

Milk thistle has also been explored for cancer prevention and high cholesterol.

Side Effects and Safety Concerns:

Side effects may include indigestion, headache and itching. Rarely, milk thistle may result in heartburn, gas, diarrhea, joint pain and sexual dysfunction.

People with allergies to daisies, artichokes, kiwi, common thistle or plants in the aster family may also be allergic to milk thistle. There have been several reports of anaphylactic shock in people who have used milk thistle products.

The safety of milk thistle in pregnant or nursing women is unknown.

Theoretically, milk thistle may lower blood sugar levels, so it should be used with caution by people with diabetes, hypoglycemia and those taking medications or supplements that affect blood sugar levels.

There is a theoretical risk that milk thistle could have an estrogen-like effect, so people with hormone-sensitive conditions such as endometriosis, uterine fibroids or cancers of the breast, uterus and ovaries should avoid milk thistle, particularly the above ground parts of the plant.

Milk thistle may reduce the effectiveness of oral contraceptives. One constituent of milk thistle can inhibit an enzyme called beta-glucuronidase, which is involved in the activity of oral contraceptives.

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