Milk thistle (Silybum marianum) has been used since Greco-Roman times as an herbal remedy for a variety of ailments, particularly liver problems. In the late 19th and early 20th centuries physicians in the United States used milk thistle seeds to relieve congestion of the liver, spleen, and kidneys. Today, several scientific studies suggest that active substances in milk thistle (particularly silymarin) protect the liver from damage caused by viruses, toxins, alcohol, and certain drugs such as acetaminophen (a common over the counter medication used for headaches and pain; acetaminophen, also called paracetamol, can cause liver damage if taken in large quantities or by people who drink alcohol regularly.)

Many professional herbalists recommend milk thistle extract for the prevention and/or treatment of various liver disorders including viral hepatitis, fatty liver associated with long term alcohol use, and liver damage from drugs and industrial toxins such as carbon tetrachloride.

Mushroom Poisoning
Milk thistle has also been used as a preventive and/or 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, the herb significantly reduces the risk of liver damage and death.

Liver disease from alcohol
A comprehensive review by the U.S. Agency for Healthcare Research and Quality (AHRQ) recently identified 16 scientific studies on the use of milk thistle for the treatment of various forms of liver disease. A European standardized extract of milk thistle was used in most of the trials.

Problems in study design (such as small numbers of participants, variations in the causes of liver disease, and differences in dosing and duration of milk thistle therapy) made it difficult to draw any definitive conclusions. However, five of seven studies evaluating milk thistle for alcoholic liver disease found significant improvements in liver function. Those with the mildest form of the disease appeared to improve the most. Milk thistle was less effective for those with severe liver disease such as cirrhosis. Cirrhosis is characterized by scarring and permanent, non-reversible damage to the liver. It is often referred to as end-stage liver disease.

Viral hepatitis
Despite the fact that milk thistle is widely used in the treatment of hepatitis (particularly hepatitis C), results from four viral hepatitis studies were contradictory. Some found improvements in liver enzyme activity while others failed to detect these benefits. None of the studies compared milk thistle with interferon or other medications for viral hepatitis.

Cancer
Preliminary laboratory studies also suggest that active substances in milk thistle may have anti-cancer effects. One active substance known as silymarin has strong antioxidant properties and has been shown to inhibit the growth of human prostate, breast, and cervical cancer cells in test tubes. Further studies are needed to determine whether milk thistle is safe or effective for people with these forms of cancer.

High cholesterol
One animal study found that silymarin (an active compound in milk thistle) worked as effectively as the cholesterol-lowering drug probucol, with the additional benefit of substantially increasing HDL ("good") cholesterol. Further studies in people are needed.

Milk thistle is native to the Mediterranean, but is now widespread throughout the world. This stout thistle usually grows in dry, sunny areas. The stem branches at the top, and reaches a height of 4 to 10 feet. The leaves are wide, with white blotches or veins. The flowers are red-purple. The small, hard-skinned fruit is brown, spotted, and shiny. Milk thistle is easy to grow, and it matures quickly, in less than a year.

The active ingredient, or liver-protecting compound in milk thistle is known as silymarin. This substance, which actually consists of a group of compounds called flavonolignands, helps 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 (important for people with liver inflammation or hepatitis), and has potent antioxidant effects.

Most milk thistle products are standardized preparations extracted from the fruits (seeds) of the plant. Most preparations are standardized to contain 70% to 80% of flavonolignans (silibinin, silychristin, and silydianin), collectively known as silymarin.

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

The silymarin in milk thistle seeds is difficult to absorb. The more concentrated the solution of silymarin, the more easily it is absorbed and the more readily it enters the bloodstream. Standardized capsules are the most concentrated form and, therefore, should be used whenever possible. Silymarin-phosphatidylcholine complex may be absorbed even more easily than regular standardized milk thistle. In clinical trials, the silymarin-phosphatidylcholine complex has worked better than silymarin by itself for treating liver disorders. A key element in cell membranes, phosphatidylcholine helps the silymarin attach easily to the cell membranes. This may keep toxins from getting inside liver cells. Alcohol extracts may be less effective and, therefore, should likely be avoided.

Pediatric

Adjust the recommended adult dose to account for the child's weight. Most herbal dosages for adults are calculated on the basis of a 150 lb (70 kg) adult. Therefore, if the child weighs 50 lb (20 to 25 kg), the appropriate dose of milk thistle for this child would be 1/3 of the adult dosage.

Adult

• Recommended dose: Generally 12 to 15 g dried herb (200 to 400 mg silymarin) per day or silymarin-phosphatidylcholine complex 100 to 200 mg two times per day.
• For liver protection: 120 mg silymarin (about 2 capsules), two times daily
• To treat liver damage (from alcohol, drugs, or chemicals): 120 mg (about 3 capsules), three times per day

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

Side effects from milk thistle happen only rarely, but may include stomach pain, nausea, vomiting, diarrhea, headache, rash or other skin reactions, joint pain, impotence, and anaphylaxis (a life-threatening allergic reaction that causes throat tightness, shortness of breath, and, possibly, loss of consciousness.) The last two reactions listed are extremely rare.

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

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.

Similar to its ability to protect against damage to the liver from alcohol and acetominophen, as discussed in the Overview, milk thistle may also protect against liver damage from the following medications:

• Antipsychotics: This group of medications used for schizophrenia 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

Other medications that may interact with milk thistle include:

Aspirin
One animal study found that milk thistle may enhance the effectiveness of aspirin in rats with liver cirrhosis. Whether this herb-drug combination has the same effect in people is not known at this time.

Chemotherapy medications
Preliminary research suggests that silybin may enhance the tumor fighting effects of cisplatin and doxorubicin when tested against breast and ovarian cancer cells.

In addition, milk thistle may protect the kidneys against toxic side effects associated with cisplatin and cyclosporine, two medications that are commonly used to treat cancer.

On the other hand, a different laboratory study revealed that the anticancer effect of cisplatin and ifosfamide was diminished in the presence of milk thistle. More research needs to be done to assess how milk thistle and cancer-fighting agents interact.

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