Many patients with chronic hepatitis C infections turn to botanical supplements when traditional medicine fails them. But one of those alternative medicines, a product called silymarin derived from the milk thistle plant, is no better than a placebo, according to a new study published Tuesday in the Journal of the American Medical Association.

Silymarin is the most common botanical treatment for liver disorders used in the U.S., and has been used in traditional medicine for centuries. A previous study of 1145 people in the journal Hepatology found that 33% of patients with chronic hepatitis C and cirrhosis were using or had used silymarin at some point.

A team led by University of North Carolina liver researcher Michael Fried conducted a clinical trial with 154 chronic hepatitis C patients, all of whom had been previously unsuccessfully treated with the current standard therapy, based on the protein interferon. Patients were assigned to one of three groups: a group that received 420 mg of silymarin 3 times daily, another that took 700mg of silymarin 3 times a day, and a group that took placebo pills three times a day.

The scientists were looking to see if any of the medicines helped the patients reach normal levels of a serum called alanine aminotransferase involved in liver function. After 24 weeks, the researchers found that only 2 patients in each group had a normal threshold of serum ALT, and there were no significant changes in physical or mental health amongst any of the groups.

In summary, oral silymarin, used at higher than customary doses, did not significantly alter biochemical or virological markers of disease activity in patients with chronic HCV infection who had prior treatment with interferon-based regimens, the authors wrote.

In a phone interview, Fried noted that their study used doses of silymarin that are higher than customarily taken, so it's unlikely that they weren't seeing any effect because the patients weren't getting enough of the extract.

This study really gives patients and health care providers the kind of information they need to make an informed decision, Fried said.

SOURCE: Fried et al. Effect of Silymarin (Milk Thistle) on Liver Disease In Patients With Chronic Hepatitis C Unsuccessfully Treated With Interferon Therapy: A Randomized Controlled Trial. JAMA 308: 274-282.