Milk Thistle Overview

The milk thistle plant commonly grows from 2 to 7 feet in height, with spiny leaves and reddish-purple, thistle-shaped flowers. It has also been called wild artichoke, holy thistle, and Mary thistle. Native to Europe, milk thistle has a long history of use as both a food and a medicine. At the turn of the twentieth century, English gardeners grew milk thistle to use its leaves like lettuce (after cutting off the spines), the stalks like asparagus, the roasted seeds like coffee, and the roots (soaked overnight) like oyster plant. The seeds and leaves of milk thistle were used for medicinal purposes as well, such as treating jaundice and increasing breast milk production.

German researchers in the 1960s were sufficiently impressed with the history and clinical effectiveness of milk thistle to begin examining it for active constituents. In 1986, Germany's Commission E approved an oral extract of milk thistle as a treatment for liver disease. However, the evidence that it really works remains incomplete and inconsistent.

As noted above, there is considerable evidence from studies in animals that milk thistle can protect the liver from numerous toxins. However, human studies of people suffering from various liver diseases have often yielded mixed results. A 2007 review of published and unpublished studies on milk thistle as a treatment for liver disease caused by alcohol or viral hepatitis concluded that benefits were seen only in low-quality trials, and, even in those, milk thistle did not show more than a slight benefit. ¹

Acute Viral Hepatitis

A 21-day, double-blind, placebo-controlled study of 57 people with acute viral hepatitis found significant improvements in the group receiving milk thistle. ² A 35-day study of 151 individuals thought to have acute hepatitis found no benefit with milk thistle, but this study has been criticized for failing to document that the participants actually had acute hepatitis. ³

Chronic Viral Hepatitis

Inconsistent evidence exists regarding whether milk thistle is helpful for chronic viral hepatitis B or C. ⁴ The herb does not appear to affect levels of virus in the body, but might help protect the liver from damage and improve some symptoms.

Alcoholic Hepatitis

A double-blind, placebo-controlled study performed in 1981 followed 106 Finnish soldiers with alcoholic liver disease over a period of 4 weeks. ⁵ The treated group showed a significant decrease in elevated liver enzymes and improvement in liver histology (the microscopic structure of liver tissue), as evaluated by biopsy in 29 subjects.

Two similar studies provided essentially equivalent results. ⁶ However, a 3-month, randomized, double-blind study of 116 people showed little to no additional benefit, perhaps because most participants reduced their alcohol consumption and almost half stopped drinking entirely. ⁷ Another study found no benefit in 72 patients followed for 15 months. ⁸ It is undoubtedly more effective for people with alcoholism to quit drinking than to continue drinking and take milk thistle!

Liver Cirrhosis

A double-blind, placebo-controlled study of 170 people with alcoholic or non-alcoholic cirrhosis found that in the group treated with milk thistle the 4-year survival rate was 58% as compared to only 38% in the placebo group. ⁹ This difference was statistically significant.

A double-blind, placebo-controlled trial that enrolled 172 people with cirrhosis for 4 years also found reductions in mortality, but they just missed the conventional cutoff for statistical significance. ¹⁰ A 2-year, double-blind, placebo-controlled study of 200 individuals with alcoholic cirrhosis found no reduction in mortality attributable to the use of milk thistle. ¹¹ However, in a analysis of 19 randomized trials, researchers concluded that milk thistle was significantly more effective at reducing mortality from liver cirrhosis (mostly alcohol-related) compared to placebo, but no more effective at reducing mortality from any cause. ¹² Other double-blind studies of people with various forms of cirrhosis have looked at changes in tests of liver function rather than mortality. Some found benefit ¹³ , while others did not. ¹⁴

Protection from Medications That Damage the Liver

Numerous medications can injure or inflame the liver. Preliminary evidence suggests that milk thistle might protect against liver toxicity caused by drugs such as acetaminophen , alcohol, phenothiazines , and phenytoin ( Dilantin ). ¹⁵ However, according to a 12-week, double-blind study of 222 people, milk thistle does not seem to prevent the liver inflammation caused by the Alzheimer's drug tacrine (Cognex). ¹⁶

The standard dosage of milk thistle is 200 mg 2 to 3 times a day of an extract standardized to contain 70% silymarin.

There is some evidence that silymarin bound to phosphatidylcholine may be better absorbed. ¹⁷ This form should be taken at a dosage of 100 mg to 200 mg twice a day.

Warning: Considering the severe nature of liver disease, a doctor's supervision is essential. Also, do not inject milk thistle preparations that are designed for oral use!

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