Milk Thistle

Silybum marianum has the strongest traditional and mechanistic credentials of any liver herb, and a clinical record that is respectable rather than spectacular — a gap worth understanding rather than papering over.

The active fraction, silymarin, is a mixture of flavonolignans dominated by silibinin. Its mechanisms are well characterised: it stabilises hepatocyte membranes and competitively blocks toxin uptake transporters, raises intracellular glutathione, scavenges reactive oxygen species, inhibits NF-kB-driven inflammatory signalling, and suppresses hepatic stellate cell activation, the step that drives fibrosis. In animal models of toxin-induced liver injury the protection is substantial.

The strongest human evidence is also the most specific. Intravenous silibinin, given as Legalon SIL, is standard care in Amanita phalloides poisoning across much of Europe, where it blocks OATP-mediated hepatic uptake of amatoxin and reduces mortality. That is a genuine pharmaceutical use, not a supplement claim, and it is worth separating from what oral capsules do.

Orally, results are mixed. Cochrane reviews of alcoholic and hepatitis B or C liver disease found no significant effect on mortality or liver histology. The SyNCH trial of high-dose oral silymarin in hepatitis C non-responders found no reduction in viral load or ALT beyond placebo. Non-alcoholic fatty liver disease is the more promising indication, with several trials showing reduced ALT and AST and some ultrasound improvement. There is also reasonable evidence for reduced hepatotoxicity during isoniazid or chemotherapy treatment, and for modest glycaemic improvements in type 2 diabetes.

Oral bioavailability is the limiting factor — silibinin is poorly water-soluble with extensive first-pass conjugation, which silybin-phosphatidylcholine complexes substantially improve.