Milk Thistle
The traditional liver herb. The extract number on the label does most of the work.
Milk thistle is a flowering plant whose seeds contain silymarin, a group of flavonolignans of which silybin is the most active, with long traditional use for liver support. Modern trials show modest hepatoprotective and antioxidant effects, though the plant's on-its-own effect is limited by poor absorption of silymarin from a standard capsule. Standardised extracts list 80% silymarin content as the reference benchmark; Siliphos and other phytosome versions bind silybin to phospholipids for meaningfully better blood levels at a lower dose. Raw milk thistle seed powder is the cheapest option but delivers unpredictable amounts of active compound.
Forms and bioavailability
Not all forms are absorbed equally. The form on your supplement label affects how much your body can actually use.
| Form | Absorption | With food | Timing | Evidence |
|---|---|---|---|---|
| milk thistle seed powder | Lower | With food | Either | Possible |
| silymarin extract (80% standardised) | Typical | With food | Either | Likely |
| silybin phytosome (Siliphos) | Higher | With food | Either | Likely |
Stack Almanac tracks which milk thistle form you're taking, since a phytosome and a plain 80% extract at the same milligram dose are not delivering the same amount of active silybin.
Track your Milk Thistle in Stack Almanac
Last reviewed: 2026-07-22. Reference values are adult-general RDAs. Individual needs may vary. This page is for informational purposes only and is not a substitute for professional medical advice.