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02Research · Supplement

Milk Thistle

Measured against the 58-marker panel. Human studies found an effect on 25, no change in 4 and conflicting results on 0; 29 have no result yet.

Most studied for

Hepatoprotection - general (NAFLD, elevated liver enzymes, toxic hepatitis, alcoholic liver disease)

  • Supported 25
  • No effect 4
  • Conflicting 0
  • No result yet 29
BOverall evidence grade
457Studies tracked
34Meta-analyses
151Randomized trials

01Read first

Who should be careful

From the dossier's safety review: 14 cautions and 18 interactions, 13 rated serious. They summarize research and labels; they are not advice for you.

Cautions14

  • SeriousAsteraceae/Compositae family allergyGrade B

    Cross-reactivity with milk thistle (Silybum marianum) in patients allergic to ragweed, chrysanthemums, marigolds, daisies. Anaphylaxis cases documented in FAERS.

  • SeriousConcurrent narrow-TI immunosuppressants (cyclosporine, tacrolimus, sirolimus, everolimus)Grade B

    CYP3A4 + P-gp inhibition significantly elevates immunosuppressant levels. Risk compounded in cirrhotic transplant recipients with disease-altered transporter expression.

  • SeriousPregnancyGrade C

    Insufficient human safety data. Silymarin crosses placenta in animal models.

  • SeriousActive biliary obstruction or acute cholangitisGrade C

    Silymarin has choleretic/cholagogue activity — stimulates bile production. In biliary obstruction, increased bile production without egress may worsen biliary pressure, pain, and infection risk.

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  • SeriousHormone-sensitive malignancies (ER+ breast cancer, uterine cancer, ovarian cancer)Grade C

    Silymarin has documented both estrogenic and anti-estrogenic activity in vitro. Net in vivo hormonal effect uncertain but may theoretically stimulate hormone-responsive tumor tissue.

  • SeriousIrinotecan therapy in UGT1A1*28 homozygotesGrade C

    UGT1A1*28/*28 already impairs SN-38 glucuronidation. Silymarin's additional UGT1A1 inhibition may compound risk of severe neutropenia and diarrhea.

  • ModerateConcurrent anticoagulation (warfarin, acenocoumarol) without INR monitoring accessGrade B

    CYP2C9 inhibition increases S-warfarin exposure. INR elevation and hemorrhagic events documented.

  • ModerateDiabetes on insulin or sulfonylureas without glucose monitoringGrade B

    Additive blood glucose lowering (AMPK activation, insulin sensitization) may precipitate symptomatic hypoglycemia.

  • ModerateHepatic decompensation — Child-Pugh C cirrhosisGrade C

    Drug interaction profile shifts in cirrhosis.

  • ModerateSevere renal impairment (eGFR <30 mL/min/1.73m²)Grade C

    Accumulation risk in CKD 4–5.

  • ModeratePre-surgical / Perioperative periodGrade C

    CYP3A4 inhibition may affect anesthetic drug metabolism (midazolam, fentanyl).

  • ModerateLactation / BreastfeedingGrade D

    Transfer into breast milk unknown; insufficient infant safety data.

  • ModeratePediatric patients (<18 years)Grade D

    No controlled safety or efficacy data in pediatric populations. CYP enzyme ontogeny and UGT maturation differences may alter drug interaction profile.

  • ModerateG6PD deficiency (high-dose or IV use)Grade D

    G6PD-deficient RBCs are more vulnerable to oxidant stress.

Interactions18

  • SeriousWarfarinGrade B

    CYP2C9 inhibition reduces S-warfarin clearance; possible CYP3A4 contribution for R-warfarin

  • SeriousCyclosporineGrade B

    Dual inhibition: CYP3A4 metabolism inhibition + P-gp efflux inhibition → reduced cyclosporine clearance

  • SeriousTacrolimusGrade C

    CYP3A4 + P-gp dual inhibition; similar mechanism to cyclosporine interaction but tacrolimus has narrower therapeutic index

  • SeriousDigoxinGrade C

    P-gp inhibition by silymarin reduces intestinal efflux and renal secretion of digoxin → elevated digoxin levels

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  • SeriousTamoxifenGrade C

    CYP2D6 inhibition reduces conversion to endoxifen (primary active metabolite); reduces efficacy in breast cancer treatment

  • SeriousSirolimus (rapamycin)Grade C

    CYP3A4 and P-gp inhibition increases sirolimus exposure

  • SeriousIrinotecanGrade C

    UGT1A1 inhibition by silymarin reduces SN-38 glucuronidation, potentially elevating active metabolite exposure and GI/hematologic toxicity

  • ModerateMidazolamGrade B

    CYP3A4 competitive inhibition by silybin and isosilybin; Ki ~5–15 µM

  • ModerateIndinavirGrade B

    CYP3A4 inhibition; P-gp inhibition reduces intestinal efflux of indinavir

  • ModerateInsulin and sulfonylureasGrade B

    Silymarin has demonstrated blood glucose-lowering effects (AMPK activation, gluconeogenesis inhibition, insulin sensitization). Additive hypoglycemic effect when combined with secretagogues or exogenous insulin.

  • ModerateSimvastatin / LovastatinGrade C

    CYP3A4 inhibition increases statin AUC → elevated myopathy/rhabdomyolysis risk

  • ModerateLosartanGrade C

    CYP2C9 inhibition impairs losartan → EXP3174 conversion; reduces antihypertensive efficacy

  • ModerateMetforminGrade C

    Silymarin may inhibit OCT1/OCT2 transporters → altered metformin hepatic and renal distribution; secondary: insulin-sensitizing synergy may cause additive hypoglycemia

  • ModerateAntidiabetic agents (sulfonylureas: glipizide, glyburide)Grade C

    CYP2C9 inhibition reduces sulfonylurea clearance; additive hypoglycemic effect from silymarin's insulin-sensitizing properties

  • ModerateBaicaleinGrade C

    Inhibits BCRP (ABCG2) and MRP2 (ABCC2) efflux transporters; reduces intestinal efflux and biliary elimination of silibinin diastereomers

  • ModerateStatins (CYP3A4-metabolized: simvastatin, lovastatin, atorvastatin)Grade C

    CYP3A4 inhibition reduces statin clearance. OATP1B1/1B3 competition may also reduce hepatic uptake of statin acids.

  • ModerateOral contraceptives (estradiol/ethinylestradiol)Grade D

    CYP3A4 inhibition may increase estrogen exposure; UGT1A1 competition may reduce glucuronide conjugation of estrogens

  • MinorOral contraceptives / exogenous estrogensGrade D

    UGT1A1 and possible SULT inhibition reduces estrogen phase II conjugation; CYP1A2 inhibition reduces estradiol metabolism.

02What it moves

29 markers studied

One row per marker on the panel that human studies measured. Open a row for the direction, who was studied, and the papers.

Read with this in mind

Disproportionate representation of Chinese, Iranian, and Eastern European study populations in the NAFLD/metabolic syndrome RCT corpus.

CONTESTED: Clinical outcome benefit in advanced cirrhosis is unproven.

CONTESTED: Bioavailability-dependent efficacy creates major comparability problem.

Blood sugar4 of 4 studied

HbA1cLowersGrade A
Fasting glucoseLowersGrade B

Milk thistle lowers fasting glucose.

Fasting insulinLowersGrade B

Milk thistle lowers fasting insulin.

HOMA-IRLowersGrade A

Milk thistle lowers HOMA-IR.

Lipids4 of 6 studied

LDL-CLowersGrade A
HDL-CRaisesGrade A
TriglyceridesLowersGrade A
Total cholesterolLowersGrade A

Inflammation3 of 5 studied

hs-CRPLowersGrade A

Milk thistle lowers hs-CRP.

IL-6LowersGrade A
TNF-αLowersGrade A

Liver6 of 6 studied

ALTLowersGrade A
ASTLowersGrade A
GGTLowersGrade A
ALPNo changeGrade A
BilirubinLowersGrade A
AlbuminRaisesGrade A

Blood and iron2 of 7 studied

HemoglobinRaisesGrade B

Milk thistle raises hemoglobin.

FerritinLowersGrade B

Milk thistle lowers ferritin.

Oxidative stress4 of 4 studied

MDALowersGrade A
F2-isoprostanesLowersGrade D

Milk thistle lowers F2-isoprostanes.

8-OHdGLowersGrade C

Milk thistle lowers 8-OHdG.

GlutathioneRaisesGrade A

Minerals1 of 5 studied

CalciumChangesGrade C

Milk thistle changes calcium.

Also measured13 outcomes

Outcomes these studies measured that are not on the shared panel, so they are not on the map.

Waist CircumferenceLowersGrade B
Fibrosis scoreLowersGrade B

Milk thistle lowers fibrosis score.

Bilirubin indirectLowersGrade B

Milk thistle lowers bilirubin indirect.

Hepatic collagenLowersGrade B

Milk thistle lowers hepatic collagen.

Hepatic steatosisLowersGrade B

Milk thistle lowers hepatic steatosis.

Serum iron absorptionLowersGrade B

Milk thistle lowers serum iron absorption.

Il2LowersGrade C

Milk thistle lowers Il2.

INRLowersGrade C

Milk thistle lowers INR.

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SOD activityRaisesGrade C

Milk thistle raises SOD activity.

Ho1 expressionRaisesGrade D

Milk thistle raises Ho1 expression.

Pparg expressionRaisesGrade D

Milk thistle raises pparg expression.

Cmyc expressionLowersGrade D

Milk thistle lowers cmyc expression.

Nf kb activityLowersGrade D

Milk thistle lowers nf kb activity.

How it might work4

Proposed mechanisms. Most rest on lab and animal work, so read them as explanations, not proof of an effect.

  • Direct ROS scavenging via flavonolignan electron donation - silybin B phenolic OH groups quench hydroxyl, superoxide, and peroxynitrite radicals at nanomolar concentrations in vitro
  • NF-kB p65 nuclear translocation inhibition → suppression of TNF-alpha, IL-1beta, IL-6, and COX-2 transcription in hepatocytes and Kupffer cells under LPS/oxidative stimulation
  • TGF-beta1/Smad2/3 signaling suppression → reduced hepatic stellate cell (HSC) activation, alpha-SMA expression, and collagen I/III synthesis → antifibrotic phenotype
  • Nrf2/ARE pathway activation → nuclear Nrf2 translocation → upregulation of HO-1, NQO1, TXNRD1, AKR1C1, catalase, SOD, and GPx gene expression → secondary endogenous GSH elevation

03No result yet

29 markers

29 markers on the panel have no result for Milk Thistle yet. A gap is not a negative result.

Not yet reviewed29

No study in this dossier reported these, and they haven't been searched for one by one yet.

Lipids
ApoBLp(a)
Inflammation
ESRFibrinogen
Hormones
SHBGDHEA-S

Open questions4

  • Does oral silymarin achieve sufficient intrahepatic concentrations to meaningfully activate the Nrf2/ARE pathway in human hepatocytes, given ~0.7-1.5% oral bioavailability of standard extract?
  • Is silymarin effective for ALT/AST reduction in obese (BMI >=30) NAFLD patients, given the null subgroup signal from Shahsavari 2025 MA?
  • What is the safety and efficacy profile of silymarin in pediatric NAFLD, which is increasing in prevalence globally?
  • What is the long-term (>2 year) safety profile of continuous silymarin supplementation at standard doses?

04The studies and genetics

Go deeper

The three acts above are free. The paper-by-paper list and the genetics findings are part of the Research plan.
Research planResearch access

Every study and gene finding

Open the strongest papers with their populations and findings, and the gene differences human studies measured.

Compare with

On the evidence map →

Each marker shows the strongest record in the dossier. Records are extracted from published studies by a model pipeline and graded A to D; records whose own notes say no usable human data exists count as no result yet. Research summaries for education, not medical advice. How this page is sourced