If milk thistle curbs liver disease, science hasn’t adequately proven it yet, according to a report in The American Journal of Gastroenterology.

Doctors from California and Europe reached that conclusion after reviewing 13 studies of milk thistle. No significant liver benefits were seen in patients with liver disease who took milk thistle.

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But the doctors aren’t totally shutting the door on milk thistle. Better studies are needed, write Andrea Rambaldi, MD, and colleagues.

Rambaldi works in Denmark at Copenhagen University Hospital. Other doctors who worked on the report are on staff at the University of California, San Francisco and San Giuseppe Moscati Hospital in Avellino, Italy.

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About Milk Thistle

Milk thistle is a flowering herb. It is touted for protecting the liver and boosting liver function.

A compound in milk thistle seeds is believed to be the biologically active part of the herb. The seeds are used to prepare capsules containing powdered herb or seed, extracts, and infusions (strong teas), states the National Center for Complementary and Alternative Medicine (NCCAM).

The NCCAM is part of the National Institutes of Health (NIH). It is funding research on milk thistle. “To date, there is no conclusive evidence to prove its claimed uses,” states the NCCAM’s web site.

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Quality Questions

The 13 trials had a combined total of 915 patients. All of the patients had liver disease caused by alcoholism and/or hepatitis B or C.

The trials, which were completed by December 2003, compared milk thistle to a fake drug (placebo). Treatments lasted an average of six months. The general quality of the trials was described as “low” by the researchers.

Patients taking milk thistle didn’t show any liver benefits.

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Significantly fewer patients taking milk thistle died from liver problems. But that pattern didn’t hold in high-quality trials, write Rambaldi and colleagues.

If milk thistle wasn’t helpful, it also wasn’t harmful. Milk thistle didn’t appear to worsen anyone’s liver disease. It wasn’t linked to any increased risk of side effects studied by Rambaldi’s team.

Many studies were poorly designed, so better trials should be done, they write.

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Meanwhile, the NCCAM reminds patients to talk to their doctors about their use of any herbal or dietary supplements, including milk thistle.

By Miranda Hitti, WebMD Medical News. Reviewed by Louise Chang, MD.

SOURCES: Rambaldi, A. The American Journal of Gastroenterology, November 2005; vol 100: p 2583. National Center for Complementary and Alternative Medicine, “Herbs at a Glance: Milk Thistle.”