Silymarin (Milk Thistle)
Silymarin is a flavonolignan complex extracted from milk thistle (Silybum marianum) seeds, of which silybin is the principal active constituent. It is one of the oldest and most popular herbal liver-support supplements and a near-universal inclusion in on-cycle 'liver stacks'. Despite very heavy use, controlled evidence of benefit in most liver conditions is weak and inconsistent.
01 Overview
Silymarin acts as an antioxidant and free-radical scavenger, stabilises hepatocyte membranes and may compete with certain toxins for cell uptake — the rationale behind intravenous silibinin use in Amanita (death-cap) mushroom poisoning, its one setting of reasonably supported benefit. It also has anti-inflammatory and mild anti-fibrotic activity in preclinical models.
PED users add it during cycles, especially with oral steroids, expecting hepatoprotection. However, randomised trials in hepatitis C, alcoholic and non-alcoholic liver disease have generally failed to show meaningful improvement in hard outcomes, and there is no direct evidence it protects against anabolic-steroid liver injury. Oral bioavailability is poor, which likely limits any real-world effect. It is cheap and very well tolerated.
02 Mechanism
Antioxidant flavonolignan complex (chiefly silybin) that scavenges free radicals, stabilises hepatocyte membranes, may block toxin uptake into hepatocytes and shows anti-inflammatory and anti-fibrotic activity in preclinical models.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| General liver support | 140–420 mg/day | Oral | Standardised to ~80% silymarin; usually split into 2-3 doses. |
| Higher supplemental use | 420–800 mg/day | Oral | Upper anecdotal range; bioavailability limits added benefit. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Antioxidant / membrane stabilisationReduces oxidative hepatocyte injury in laboratory models; human hard-outcome translation is weak. | in vitro / animal | Preclinical | |
| Benefit in Amanita poisoningIV silibinin is used adjunctively in death-cap mushroom poisoning, its best-supported indication — not applicable to routine cycle use. | setting-specific | Observational |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Mild GI upsetOccasional bloating, nausea or a laxative effect. | Mild | Uncommon | Observational | |
| Overreliance / unproven protectionRandomised trials do not show reliable liver protection, yet users may treat it as adequate cover for hepatotoxic orals. | Moderate | Situational | Anecdotal |