Silybin (also spelled silibinin) is the major active constituent of silymarin, an extract from the seeds of the milk thistle plant (Silybum marianum). Its use to support the hepatic (liver) system has both traditional and scientific backing, but significant scientific validation exists, particularly in animal models and limited human studies. Silybin is known for its antioxidant, anti-inflammatory, and antifibrotic effects on liver cells. It is believed to protect hepatocytes (liver cells) from toxins, reduce oxidative stress, and support regeneration of damaged liver tissue.

Clinical trials and meta-analyses have shown that silymarin (containing silybin as a major component) may improve liver enzyme levels in patients with liver diseases such as nonalcoholic fatty liver disease (NAFLD), hepatitis, and cirrhosis. Some studies indicate a reduction in markers of liver damage and improvement in symptoms, although evidence regarding effects on long-term clinical outcomes (e.g., mortality or progression to liver failure) is mixed and often limited by small sample sizes or study quality. Silybin’s mechanisms include inhibition of lipid peroxidation, enhancement of protein synthesis, and stabilization of hepatocyte membranes.

Major guidelines acknowledge the relative safety of silymarin/silybin, though they note the need for more robust clinical trials to confirm efficacy. Overall, the scientific evidence is supportive but not definitive, justifying a moderately high evidence rating.