Cancer Health Center

This complementary and alternative medicine (CAM) information summary provides an overview of the use of milk thistle as a treatment and adjunct agent for people with cancer.

The summary includes a brief history of milk thistle, a review of the laboratory studies and clinical trials, and a description of adverse effects associated with milk thistle use.

This summary contains the following key information:

• Milk thistle is a plant whose fruit and seeds have been used for more than 2,000 years as a treatment for liver and biliary disorders.
• The active substance in milk thistle, silymarin, is a mixture of flavonolignans, primarily consisting of four isomers: silybin, isosilybin, silychristin (also known as silichristin), and silydianin (also known as silidianin). In the biological literature, silybin is referred to as silibinin.
• Laboratory studies demonstrate that silymarin functions as an antioxidant, stabilizes cellularmembranes, stimulates detoxification pathways, stimulates regeneration of liver tissue, inhibits the growth of certain cancer cell lines, exerts direct cytotoxic activity toward certain cancer cell lines, and may increase the efficacy of certain chemotherapy agents.
• Human clinical trials have investigated milk thistle or silymarin primarily in individuals with hepatitis or cirrhosis.
• Few adverse side effects have been reported for milk thistle, but little information about interactions with anticancer medications or other drugs is available.
• Milk thistle is available in the United States as a dietary supplement.

Many of the medical and scientific terms used in the summary are hypertext linked (at first use in each section) to the NCI Dictionary of Cancer Terms, which is oriented toward nonexperts. When a linked term is clicked, a definition will appear in a separate window. All linked terms and their corresponding definitions will appear in a glossary in the printable version of the summary.

Reference citations in some PDQ CAM information summaries may include links to external Web sites that are operated by individuals or organizations for the purpose of marketing or advocating the use of specific treatments or products. These reference citations are included for informational purposes only. Their inclusion should not be viewed as an endorsement of the content of the Web sites, or of any treatment or product, by the PDQ Cancer CAM Editorial Board or the National Cancer Institute.