Silymarin (milk thistle)

Silymarin is a mixture of six flavonolignans from the fruit of the milk thistle. The most important component is called silibinin. In cell assays it acts as a radical scavenger and is said to stabilise the membrane of the liver cell, so that less toxin gets in.

It is by far the best known liver preparation and at the same time one of the most poorly supported. This page says so openly, because the alternative would be selling you a benefit the studies do not deliver.

This information is for research and educational purposes only. No medical advice.

Part of the problem is absorption. Silymarin is poorly water-soluble and oral bioavailability is correspondingly low. Preparations with a phosphatidylcholine complex or as a silibinin phytosome improve this considerably. Anyone taking plain silymarin should combine it with a meal containing fat, otherwise even less arrives.

That is also a possible explanation for the negative trials: it may be that in several investigations simply too little drug reached the place it was meant to act. That cannot be proven, and a hypothesis does not replace a result.

One use is cleanly documented: intravenous silibinin in death cap mushroom poisoning. That is an established emergency application and has little to do with the capsule.

The two methodologically strongest investigations came out negative. SyNCH (JAMA 2012) gave 154 hepatitis C patients high-dose silymarin or placebo over 24 weeks. Two participants in each group reached the primary endpoint. No effect on ALT, viral load or quality of life.

In alcoholic liver cirrhosis (J Hepatol 1998) survival under silymarin and placebo was identical across 200 patients. The Cochrane review (2007) reaches the same conclusion across 18 trials with 1,088 patients: no significant effect on mortality or histology. The apparent effect disappears once only the high-quality trials are considered.

In non-alcoholic steatohepatitis (Clin Gastroenterol Hepatol 2017) the primary endpoint was missed in 99 patients over 48 weeks. A secondary fibrosis finding was positive, but secondary endpoints are signals, not proof.

There is a widely cited positive trial from 1989 showing a survival advantage. It had 170 participants, the p-value sat just under the significance threshold, and the effect never reappeared in any of the later, larger and better trials. That is the classic pattern of a chance finding.

• Very good tolerability: across all trials the side effect profile sat at placebo level. That is the strongest point of this substance.
• Mild digestive complaints: occasional, usually temporary.
• Allergic reactions: rare, possible with an allergy to the daisy family.
• The real risk: lulling yourself into false security. Silymarin does not replace cycle limits or bloodwork.

Store dry, at room temperature and protected from light. Keep out of reach of children.