Milk thistle (Silybum marianum) has been used for 2,000 years as an herbal remedy for a variety of ailments, particularly liver, kidney, and gall bladder problems. Several scientific studies suggest that substances in milk thistle (especially a flavonoid called silymarin) protect 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.
Liver disease from alcohol
Milk thistle is often suggested as a treatment for alcoholic hepatitis and alcoholic cirrhosis. But scientific studies show mixed results. Most studies show milk thistle improves liver function and increases survival in people with cirrhosis or chronic hepatitis. 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 hard to draw any firm conclusions.
Milk thistle is widely used in the treatment of viral hepatitis (particularly hepatitis C). However, studies show mixed results. Some studies found improvements in liver function, while others did not. In one study of 16 patients who didn't respond to interferon and ribavirin therapy, milk thistle significantly reduced the viral load of hepatitis C. In 7 of the subjects the virus decreased to undetectable levels after 14 days of therapy.
Based on traditional use, milk thistle has been used as an emergency antidote for poisoning by death cap 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, it significantly reduces the risk of liver damage and death.
Early laboratory studies 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 reproducing
- Shorten the lifespan of cancer cells
- Reduce blood supply to tumors
Some studies suggest silymarin may favorably supplement sunscreen protection and may help reduce the risk of skin cancer. Other studies suggest milk thistle acts synergistically with chemotherapy. More studies are needed to show whether milk thistle has any effects in the body (not just in test tubes).
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