Milk Thistle
Silybum marianum
Also known as: Holy Thistle, Mary Thistle, Marian Thistle
Overview
One of the most extensively researched liver botanicals, though the evidence is narrower than the marketing. Silymarin, the seed extract, is a complex of flavonolignans rather than a single compound. Some fatty-liver and viral-hepatitis trials show modest liver-enzyme (ALT/AST) improvements, but NIH reviewers call the overall evidence conflicting, and Cochrane reviews found no proven effect on survival or liver damage in hepatitis and alcohol-related liver disease, with a 2025 review grading the fatty-liver enzyme benefit very low certainty. Pooled trials show no significant benefit for drug-induced or alcohol-related liver injury; one short-term signal alongside tuberculosis drugs was gone by week 8. There is no human evidence it removes heavy metals — it is not a chelator. An intravenous hospital form of silibinin is an established antidote for death-cap mushroom poisoning, an emergency use that does not transfer to oral capsules. Best understood as a well-tolerated botanical that supports the liver's own antioxidant defenses, not a proven treatment for liver damage.
Proposed mechanism
Silymarin, a mixture of flavonolignans (silybin, silychristin, silydianin), acts primarily as an antioxidant. In animal and cell-culture studies it inhibits lipid peroxidation in liver cell membranes, increases liver glutathione, and stimulates ribosomal RNA polymerase I activity and hepatocyte regeneration following liver injury. These mechanisms come from rat and in-vitro models and have not been confirmed in humans. In people, randomized trials in fatty liver disease show silymarin modestly lowers ALT and AST, though those trials are mostly small and of low-to-moderate quality. Where human trials have taken before-and-after liver biopsies, silymarin has not improved liver tissue: two placebo-controlled trials in nonalcoholic steatohepatitis missed their primary histologic endpoints, and a Cochrane review of 18 trials in alcoholic and viral liver disease found no significant effect on mortality, complications of liver disease, or liver histology.
Mechanisms describe how researchers think a compound may act, often from laboratory work — a proposed mechanism is not proof of a clinical effect in people.
Traditional & studied uses
Related pathways
Pathway tags are a research aid for browsing the glossary — they are not a claim that this ingredient treats any condition.