Silymarin is an extract of milk thistle. Millions of people use this herbal remedy to treat chronic liver disease but it doesn't do much for patients, according to a new study.

Milk thistle fruit extracts have been widely used by patients in treating liver disease based on previous evidence showing that it has anti-inflammatory, anti-oxidant, and potentially anti-viral properties so the new study set out to assess true efficacy in a group of hepatitis C patients who were previously unsuccessfully treated with interferon-based therapy – the standard anti-viral method used to treat the disease. 

The Centers for Disease Control and Prevention (CDC) estimates that 3.2 million persons in the United States have chronic hepatitis C virus (HCV) infection - 33 percent of those people have reported current or past use of silymarin to treat the disease. The new study was designed to measure the potential benefit of increasing doses of silymarin in patients with chronic HCV. To determine efficacy, researchers monitored levels of serum alaninie aminotransferase (ALT) – the enzyme found in the blood stream that is most often tested to identify liver disease. Low levels of ALT are normally found in the blood, but are elevated when the liver is damaged or diseased. Secondary outcomes included quality-of-life measures. 

The trial, which included 154 adult participants with chronic HCV, was conducted over the course of two years at four medical centers in the United States. Participants were randomly assigned to receive 420mg silymarin, 700mg silymarin or a matching placebo administered three times/week for 24 weeks, a standard duration of treatment. After 24 weeks, researchers found only two participants in each treatment group achieved lowered ALT levels. Neither the average decline in ALT activity nor quality-of-life measures at the end of treatment differed significantly across the treatment groups.

"By all indications, silymarin is no more effective at treating hepatitis C related chronic liver disease, in those who failed standard therapy with interferon, than a placebo," said K. Rajender Reddy, MD, professor of Medicine and medical director of Liver Transplantation at Penn Medicine, and senior author of the study. "This is a landmark study as millions of people around the world are looking for supplements and other forms of alternative medicines to help reduce ALT levels every year. "These data show that even higher-than-normal doses of silymarin don't significantly reduce ALT levels for patients with HCV."

The doses used in the trial were three and five times higher than the customary dose. "At the end of the trial we saw no significant changes in physical or mental health assessments between the patients who received treatment, and those who did not. Quality-of-life measures were also largely unchanged."

Published in The Journal of the American Medical Association