Milk thistle (Silybum marianum) has been used for 2,000 years as an herbal remedy for a variety of ailments, particularly liver problems. Several scientific studies suggest that substances in milk thistle (especially a flavonoid called silymarin) protects the liver from toxins, including certain drugs such as acetaminophen (Tylenol), which can cause liver damage in high doses. Silymarin has antioxidant and anti-inflammatory properties, and it may help the liver repair itself by growing new cells.

Although a number of animal studies demonstrate that milk thistle can be helpful in protecting the liver, results in human studies are mixed.

Mushroom Poisoning

Milk thistle has been used as an emergency antidote to poisoning by deathcap mushroom (Amanita phalloides). Animal studies have found that milk thistle extract completely counteracts the toxic effects of the mushroom when given within 10 minutes of ingestion. If given within 24 hours of ingestion, it significantly reduces the risk of liver damage and death.

Liver disease from alcohol

Although milk thistle is often suggested as a treatment for alcoholic hepatitis and alcoholic cirrhosis, scientific studies show mixed results. Some studies show improvements in liver function and survival rate. But problems in the design of the studies (such as small numbers of participants and differences in dosing and duration of milk thistle therapy) make it difficult to draw any real conclusions.

Viral hepatitis

Although milk thistle is widely used in the treatment of viral hepatitis (particularly hepatitis C), results from four studies were contradictory. Some found improvements in liver function, while others did not. None of the studies compared milk thistle with interferon or other medications for viral hepatitis.

Cancer

Early laboratory studies also suggest that silymarin and other active substances in milk thistle may have anti-cancer effects. These substances appear to stop cancer cells from dividing and proliferating, shorten their life span, and reduce blood supple to tumors. More studies are needed, however, to show whether milk thistle has any effects in the body (not just test tubes).

Milk thistle is native to the Mediterranean region, and is now found throughout the world. This stout thistle usually grows in dry, sunny areas. The spiny stems branch at the top, and reach a height of 4 to 10 feet. The leaves are wide, with white blotches or veins. Milk thistle gets its name from the milky white fluid that comes from the leaves when they are crushed. The flowers are red-purple. The small, hard-skinned fruit is brown, spotted, and shiny. Milk thistle spreads quickly (it is considered a weed in some parts of the world), and it matures quickly, in less than a year.

The active ingredient, or liver-protecting compound, in milk thistle is known as silymarin. Silymarin is actually a group of flavonoids (silibinin, silidianin, and silicristin), which are thought to help repair liver cells damaged by alcohol and other toxic substances. Silymarin also keeps new liver cells from being destroyed by these same substances, reduces inflammation (which is why it is often suggested for people with liver inflammation or hepatitis), and is a potent antioxidant.

Most milk thistle products are standardized preparations made from the seeds of the plant. Most preparations are standardized to contain 70 - 80% of silymarin.

• Capsules of standardized dried herb (each capsule contains about 120 - 140 mg silymarin)
• Liquid extract
• Tincture
• Silymarin phosphatidylcholine complex

A few studies show that a silymarin-phosphatidylcholine complex may be absorbed more easily than regular standardized milk thistle. A key element in cell membranes, phosphatidylcholine helps silymarin attach easily to cell membranes. This may keep toxins from getting inside liver cells. Alcohol extracts should be avoided by anyone with alcohol-related liver disease.

Pediatric

There are no studies showing whether it is safe to give milk thistle to a child. Liver problems can be serious and should be diagnosed by a physician. Talk to your doctor before giving milk thistle to a child.

Adult

If you think you have a liver problem, you should see a doctor, as liver disease can be life-threatening.

• Recommended dose: 200 - 400 mg one to three times per day or silymarin-phosphatidylcholine complex 100 - 200 mg two times per day.

The use of herbs is a time-honored approach to strengthening the body and treating disease. Herbs, however, can trigger side effects and can interact with other herbs, supplements, or medications. For these reasons, herbs should be taken with care, under the supervision of a health care practitioner.

Side effects are usually mild and may involve stomach upset and diarrhea. Some people may get a rash from touching milk thistle plants.

Milk thistle should not be used by pregnant or breastfeeding women.

People with a history of hormone-related cancers, including breast and uterine cancer and prostate cancer, should not take milk thistle.

If you are currently being treated with any of the following medications, you should not use milk thistle without first talking to your healthcare provider.

• Antipsychotics -- includes butyrophenones (such as haloperidol) and phenothiazines (such as chlorpromazine, fluphenazine, and promethazine)
• Phenytoin -- a medication used for seizures
• Halothane -- a medication used during general anesthesia

Milk thistle may interfere with the following medications, because both milk thistle and these medications are broken down by the same liver enzymes:

• Allergy drugs -- such as fexofenadine (Allegra)
• Drugs for high cholesterol -- such as lovastatin (Mevacor, Altocor)
• Anti-anxiety drugs -- including alprazolam (Xanax), diazepam (Valium), and lorazepam (Ativan)
• Antiplatelet and anticoagulant drugs (blood thinners) -- including clopidogrel (Plavix) and warfarin (Coumadin)
• Some cancer drugs

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