Milk Thistle (Silymarin)
Silybum marianum
A traditional liver herb with antioxidant flavonolignans — helps liver enzymes in fatty liver, but unproven for serious liver disease.
Mixed evidence
🛡️Gut & Immune
Evidence tier
Mixed
Research weight
Citations
21 verified / 21
Classification
Gut & Immune
❝
What the evidence says. Conflicting results across studies; benefit uncertain.
What is Milk Thistle (Silymarin)?
Milk Thistle (Silymarin) (Silybum marianum) is a gut and immune supplement used for may modestly lower elevated liver enzymes (alt/ast) in non-alcoholic/metabolic fatty liver disease, though changes are surrogate markers, not proven clinical outcomes. NutriDex grades the human evidence as Mixed. Milk thistle (Silybum marianum) is one of the most widely used herbal liver remedies, and its standardized extract, silymarin, is a mixture of antioxidant flavonolignans (chiefly silibinin). Recent meta-analyses in non-alcoholic/metabolic fatty liver disease report statistically significant but modest reductions in liver enzymes (roughly 12–17 IU/L lower ALT and AST), but these are biochemical surrogates rather than proven improvements in liver structure, symptoms, or survival. In contrast, a Cochrane review of alcoholic and hepatitis B/C liver disease found no significant effect on mortality once low-quality trials were excluded, and a rigorous JAMA-published RCT in chronic hepatitis C found that even high doses did not lower ALT or viral load more than placebo. The overall evidence is therefore mixed: promising for liver-enzyme surrogates in fatty liver but inconclusive for clinically meaningful outcomes in viral and alcoholic liver disease. Silymarin is consistently well tolerated, with mostly mild gastrointestinal effects, which has made it a popular but unproven liver "support" supplement.
Purported Benefits
✓May modestly lower elevated liver enzymes (ALT/AST) in non-alcoholic/metabolic fatty liver disease, though changes are surrogate markers, not proven clinical outcomes
✓Provides antioxidant and anti-inflammatory activity in liver tissue (mechanistic and preclinical data)
✓Generally well tolerated, making it a low-risk adjunct for those seeking liver support
✓Possible small improvements in triglycerides and HDL in fatty-liver populations (preliminary)
✓Does NOT reliably improve survival or disease course in alcoholic or hepatitis B/C liver disease — benefits for these are unproven
Evidence by outcome
The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.
| Outcome | Evidence | Effect | Studies |
|---|---|---|---|
| Lower liver enzymes (ALT/AST) in NAFLD/MASLDMultiple MASLD meta-analyses show significant ALT/AST reductions (~12-17 IU/L), but these are surrogate markers, not clinical outcomes. | Moderate | ↑ benefit · small | 5 |
| No survival benefit in alcoholic / viral (HBV/HCV) liver diseaseCochrane found no mortality effect once low-quality trials excluded; a JAMA hepatitis-C RCT showed no ALT or viral-load benefit. | Moderate | — no effect · negligible | 2 |
| Improved triglycerides / HDL (fatty liver)Modest lipid improvements reported in MASLD meta-analyses, but lipid benefit appears mainly as add-on therapy, not monotherapy. | Preliminary | ↑ benefit · small | 2 |
| Lower fasting glucose / HbA1c (type 2 diabetes)5-RCT meta-analysis shows sizeable glucose/HbA1c drops, but authors graded the evidence low to very low quality with high heterogeneity. | Preliminary | ↑ benefit · moderate | 1 |
| Reduced anti-tuberculosis drug-induced liver injury5-RCT meta-analysis found ~67% relative risk reduction at week 4; single prophylaxis context, needs confirmation. | Preliminary | ↑ benefit · moderate | 1 |
| IV silibinin for Amanita mushroom poisoningCase-series review reports ~93% survival vs >20% historical mortality; observational, not a controlled trial, and IV-specific. | Preliminary | ↑ benefit · large | 1 |
Dosing & Compounds
Typical Dose
Typically 140 mg silymarin 2–3 times daily (about 280–420 mg/day) of standardized extract (~70–80% silymarin); trials have used up to 700 mg three times daily safely.
Active Compounds
Safety & Cautions
Generally well tolerated; the most common adverse effects are mild gastrointestinal symptoms (bloating, nausea, gas, occasional diarrhea). Allergic reactions can occur in people sensitive to the Asteraceae/Compositae family (ragweed, daisies, marigolds, chrysanthemums). Silymarin has limited but real potential for drug interactions: in vitro it can inhibit CYP2C9, so caution is advised with narrow-therapeutic-index drugs metabolized by this enzyme (e.g., warfarin — possible increased bleeding risk). Use during pregnancy and breastfeeding is not recommended due to insufficient human safety data. People with diabetes should monitor blood glucose, as silymarin may have mild glucose-lowering effects. Importantly, milk thistle should not be used as a substitute for evidence-based treatment of hepatitis, cirrhosis, or alcoholic liver disease; anyone with diagnosed liver disease should consult a clinician before use. Standardize products and avoid unverified high-dose preparations. Educational only — always check with your doctor or pharmacist before combining Milk Thistle (Silymarin) with any medicine.
Milk Thistle (Silymarin) drug interactions
Known or theoretical interactions between Milk Thistle (Silymarin) and common medications — educational, not exhaustive. Always check with your doctor or pharmacist before combining Milk Thistle (Silymarin) with any medicine.
Monitor
Narrow-margin drugs (e.g. warfarin)
Usually benign, but silymarin may modestly affect drug metabolism; monitor narrow-index drugs like warfarin.
Silymarin can weakly inhibit CYP2C9 and glucuronidation, potentially raising some drug levels. NCCIH — Milk Thistle
Key Studies ★ 21 studies
Systematic review
29 RCTs, 3,846 participants
✓ PubMed
In this 2023 systematic review of trials across diverse liver conditions, 65.5% of studies reported reduced liver enzymes with silymarin, 20.7% showed no change, and 13.8% showed increases — indicating inconsistent, condition-dependent effects.
Meta-analysis
9 trials, 820 patients
✓ Full text
This 2024 meta-analysis in MASLD/NAFLD found silymarin significantly reduced ALT by ~17 IU/L and AST by ~13 IU/L versus control, with larger reductions after 6 months, plus modest triglyceride and HDL improvements.
meta-analysis
33 RCTs, 1,943 participants
✓ PubMed
This 2024 systematic review and dose-response meta-analysis in Antioxidants found silymarin supplementation significantly reduced total cholesterol, LDL, triglycerides, fasting glucose, HbA1c, and systolic blood pressure, supporting modest beneficial effects on multiple cardiometabolic risk factors.
Meta-analysis
Zhong 2024 (Can Liver J)
✓ PubMed
Systematic review and meta-analysis of 9 trials in MASLD found silymarin significantly reduced ALT (MD -17.12 U/L, 95% CI -28.81 to -4.43, p<0.004) and AST (MD -12.56 U/L, 95% CI -19.02 to -6.10, p<0.0001).
Meta-analysis
BMC Complement Med Ther 2025
✓ Full text
Meta-analysis of 55 RCTs (3,545 patients) found silymarin significantly reduced ALT (SMD -0.912, 95% CI -1.177 to -0.646) and AST (SMD -0.670, 95% CI -0.931 to -0.408), with greatest effect at doses <400 mg/day for <=2 months, no effect on ALP.
Meta-analysis
Food Sci Nutr 2024
✓ Full text
Systematic review and meta-analysis (7 silymarin trials, ~566 participants) found silymarin lowered ALT (MD -6.44 U/L, 95% CI -10.03 to -2.85, p=0.0004) and AST (MD -6.99 U/L, 95% CI -8.56 to -5.42, p<0.00001) in MASLD.
meta-analysis
8 studies, 477 patients
✓ PubMed
This 2021 systematic review and meta-analysis in Expert Review of Clinical Pharmacology found that adding silymarin to standard iron chelators significantly reduced serum ferritin in transfusion-dependent beta-thalassemia patients versus chelators alone, indicating improved iron-overload control.
Meta-analysis
Kalopitas et al. 2021 (Nutrition)
✓ PubMed
Systematic review/meta-analysis of 8 RCTs in NAFLD: silymarin produced a statistically significant greater reduction in transaminases (ALT and AST) versus placebo, independent of weight loss; authors caution on the modest quality of included trials.
meta-analysis
5 RCTs, 270 patients
✓ Full text
This 2016 systematic review and meta-analysis in Journal of Diabetes Research found that silymarin in type 2 diabetes significantly lowered fasting blood glucose by 26.86 mg/dL (95% CI -35.42 to -18.30) and HbA1c by 1.07% (95% CI -1.73 to -0.40), though the authors graded the evidence as low to very low quality.
meta-analysis
5 RCTs, 1,198 patients
✓ Full text
This 2019 meta-analysis in Canadian Journal of Gastroenterology & Hepatology found prophylactic silymarin significantly reduced antituberculosis drug-induced liver injury at week 4 (RR 0.33, 95% CI 0.15-0.75), a roughly 67% relative risk reduction versus placebo.
meta-analysis
10 trials
✓ PubMed
This 2019 systematic review and meta-analysis of clinical trials found silymarin reduced total cholesterol, LDL, and triglycerides primarily when combined with other lipid-lowering treatments rather than as monotherapy, with no significant effect on HDL.
Meta-analysis
Voroneanu et al. 2016 (J Diabetes Res)
✓ PubMed
Systematic review/meta-analysis of 5 RCTs (270 patients) in type 2 diabetes: silymarin significantly reduced fasting blood glucose (-26.86 mg/dL; 95% CI -35.42 to -18.30) and HbA1c (-1.07%; 95% CI -1.73 to -0.40), with no effect on lipid profile; evidence quality low with high heterogeneity, so no formal recommendation.
Guideline
Gillessen et al. 2022 (International Consensus)
✓ PubMed
International expert-panel consensus recommendations: based on preclinical/clinical evidence of antioxidant, anti-inflammatory, and antifibrotic effects, endorses silymarin as a hepatoprotective antioxidant agent for toxic liver disease (alcoholic liver disease, NAFLD/MAFLD, drug-induced liver injury, cirrhosis), with lifestyle modification remaining the cornerstone of fatty liver disease management.
Cochrane systematic review
13 RCTs, 915 participants
✓ Full text
This Cochrane review found no significant effect of milk thistle versus placebo on all-cause mortality (RR 0.78, 95% CI 0.53–1.15) in alcoholic and/or hepatitis B/C liver disease, with apparent benefits disappearing in high-quality trials.
rct
Randomized placebo-controlled trial in breast cancer patients
✓ Full text
This 2024 randomized, placebo-controlled trial in BMC Complementary Medicine and Therapies found silymarin 140 mg/day during chemotherapy produced hepatoprotective effects on certain liver parameters (notably alkaline phosphatase and bilirubin), suggesting improved liver function versus placebo.
RCT
Wah Kheong et al. 2017 (NASH RCT)
✓ PubMed
Double-blind RCT, 99 biopsy-proven NASH patients, silymarin 700 mg TID x 48 wk. Did NOT meet primary endpoint (>=30% NAS reduction: 32.7% vs 26.0% placebo, P=.467), but significantly more silymarin patients had >=1-point fibrosis reduction on histology (22.4% vs 6.0%, P=.023) and >=30% liver-stiffness reduction (24.2% vs 2.3%, P=.002); safe and well tolerated.
Randomized controlled trial
154 patients
✓ PubMed
In this multicenter double-blind RCT in chronic hepatitis C unresponsive to interferon, oral silymarin (420 or 700 mg three times daily for 24 weeks) did not reduce serum ALT or HCV RNA more than placebo.
rct
82 patients (crossover RCT)
✓ PubMed
In this crossover randomized controlled trial in beta-thalassemia major, silymarin 420 mg/day for 12 weeks significantly decreased the inflammatory markers CRP and IL-6 and raised anti-inflammatory IL-10 compared with placebo.
Safety review
Narrative/safety review
✓ PubMed
This updated safety review concluded silymarin is well tolerated even at high doses (700 mg three times daily for 24 weeks), with mostly mild gastrointestinal effects and limited cytochrome P450-mediated drug interactions.
review
1,491 documented cases
✓ Full text
This 2012 review in Current Pharmaceutical Biotechnology reported that intravenous silibinin (Legalon SIL) as antidote for Amanita amatoxin poisoning was associated with under 10% mortality (about 93% survival) versus historical mortality above 20%, by blocking hepatic re-uptake of the toxin.
authoritative-database
NIH LiverTox safety assessment
✓ Full text
The NIH LiverTox database assigns milk thistle/silymarin a likelihood score of E (unlikely cause of clinically apparent liver injury), concluding that despite widespread use it has not been implicated in causing serum enzyme elevations or acute liver injury.