Milk Thistle: How Much Do You Actually Need for Liver Protection?

Milk thistle is the most widely used liver supplement ingredient in the world. It is also one of the most frequently underdosed. Here is what the clinical evidence says about how much you actually need — and why the form matters as much as the dose.

What Is Milk Thistle?

Milk thistle (Silybum marianum) is a flowering herb native to the Mediterranean region. Its seeds contain a group of flavonolignans collectively known as silymarin — the active compounds responsible for its hepatoprotective effects. When supplement labels list "milk thistle extract," they are typically referring to a standardised extract containing 70–80% silymarin.

How Does Silymarin Protect the Liver?

Silymarin exerts its hepatoprotective effects through three primary mechanisms:

The Dose Question

The most commonly studied dose of silymarin for liver health is 200–400mg per day, typically divided into two or three doses. A 2005 Cochrane review of 13 randomised controlled trials found that silymarin at this dose range consistently reduced ALT and AST levels in patients with alcoholic and non-alcoholic liver disease.

However, many commercial milk thistle supplements provide only 50–150mg of silymarin per day — well below the studied range. When evaluating a supplement, look at the silymarin content (not just the total milk thistle extract weight) and verify it falls within the 200–400mg range.

The Bioavailability Problem

Standard milk thistle extract has notoriously poor bioavailability. Silymarin is poorly water-soluble, and studies suggest that only 20–50% of an oral dose is absorbed. This is why patented delivery systems have been developed to improve absorption.

The most clinically validated of these is Siliphos® (silybin-phosphatidylcholine complex), which achieves up to 10x greater bioavailability than standard silymarin extract. A 2006 study in the European Journal of Drug Metabolism and Pharmacokinetics demonstrated that Siliphos® produced significantly higher plasma silybin concentrations than equivalent doses of standard extract.

Our Recommendation

For liver protection, look for a supplement that provides at least 200mg of standardised silymarin (70–80% extract) per day. If bioavailability is a priority, Siliphos® is the gold standard — but it comes at a premium. For comprehensive liver support that goes beyond milk thistle alone, Cloud9 Daily Restore combines 250mg of milk thistle with NAC, DHM, and Benfotiamine for a more complete approach.