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Milk Thistle

Most recognized for its traditional use and studied applications in supporting liver health.

Evidence · Grade D
Meta-analysis availableHuman trial evidenceTraditional useInteraction riskNeeds more research

Silybum marianum, the most studied herb for liver health; investigated for chemoprotection during chemotherapy.

Milk thistle (Silybum marianum) is an herb native to the Mediterranean region, primarily recognized for its seeds, which contain the active complex silymarin. It has been traditionally used for liver support and is commonly consumed as an oral supplement in capsule or extract form. Users often seek it for perceived benefits related to liver health and detoxification. Modern applications often involve its use in managing various liver conditions.

Quick answer

What it is: Milk thistle (Silybum marianum) is an herb native to the Mediterranean region, primarily recognized for its seeds, which contain the active complex silymarin.

May support:Estrogen Dominance, Psoriasis, Non-Alcoholic Fatty Liver Disease (NAFLD), Non-Alcoholic Fatty Liver Disease (NAFLD), Liver Disease, Cancer (Adjunctive Support), Mold Illness / CIRS

Evidence:Evidence · Grade D

Evidence Summary

Evidence · Grade D

The D grade for milk thistle reflects a body of evidence that includes some randomized controlled trials, albeit often with methodological limitations, alongside extensive preclinical research and traditional use. This grade suggests some promising signals but indicates a need for more robust human data to confirm efficacy.

Last reviewed · Jun 2026

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Why It Works

Milk thistle, primarily through its active compound silymarin, appears to exert protective effects on the liver by stabilizing cell membranes and acting as an antioxidant. It may also support the liver's regenerative processes.

How it works in more detail

The hepatoprotective effects of silymarin are primarily attributed to its ability to stabilize hepatocyte membranes, which may prevent toxins from entering liver cells. Silymarin is also recognized for its potent antioxidant activity, scavenging free radicals and increasing the levels of endogenous antioxidants like glutathione. Furthermore, preclinical studies suggest it may stimulate protein synthesis and promote the regeneration of liver cells. Some research indicates modulation of inflammatory pathways and inhibition of fibrogenic processes.

How to use

Always consult a qualified clinician.

Editorial guidance

Suggested dosage
500–1000 mg/day standardized to 60% silymarin, with meals.
Research dosage range
200–600 mg/day of silymarin, typically in divided doses
Typical onset
Effects of milk thistle are generally not acute; reported benefits, particularly for liver support, are typically observed after weeks or months of consistent daily supplementation.
Typical forms
capsule, tablet, tincture, tea
Quality markers
A quality milk thistle product should ideally be standardized to contain a specific percentage of silymarin, often 70-80%. Third-party testing for purity and potency is a strong indicator of quality. Some products may specify the ratio of different silymarin isomers, such as silybin, which is considered highly active.
Medication interactions
  • Cytochrome P450 metabolized drugs (potential for altered metabolism)
  • Oral contraceptives (potential for altered efficacy)
  • Anticoagulants (theoretical increased bleeding risk)
  • Diabetes medications (potential for altered blood sugar levels)
Avoid if
  • Allergy to Asteraceae/Compositae family plants
  • Pregnancy (limited data)
  • Breastfeeding (limited data)
  • Hormone-sensitive conditions (e.g., breast cancer, uterine fibroids) due to potential estrogenic effects

Community tips

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Suggested dosage

500–1000 mg/day standardized to 60% silymarin, with meals.

General guidance — discuss specifics with a clinician.

Active medicinal compounds

Silymarin (silibinin, silidianin, silicristin).

Traditional use

European folk medicine for liver and gallbladder ailments for 2,000+ years.

Safety

Safety warnings

Generally safe; mild GI upset. Caution with hormone-sensitive conditions.

Avoid if

  • Allergy to Asteraceae/Compositae family plants
  • Pregnancy (limited data)
  • Breastfeeding (limited data)
  • Hormone-sensitive conditions (e.g., breast cancer, uterine fibroids) due to potential estrogenic effects

Medication interactions

  • Cytochrome P450 metabolized drugs (potential for altered metabolism)
  • Oral contraceptives (potential for altered efficacy)
  • Anticoagulants (theoretical increased bleeding risk)
  • Diabetes medications (potential for altered blood sugar levels)

Reported side effects

  • Mild gastrointestinal upset
  • Diarrhea
  • Nausea
  • Bloating
  • Headache
  • Allergic reactions (rare)

General guidance — discuss specifics with a clinician.

Evidence ecosystem

Scientific literature, clinical guidance, government sources, ongoing research, traditional use, and lived experience — grouped by source type and quality.

Overall grade (D)

The D grade for milk thistle reflects a body of evidence that includes some randomized controlled trials, albeit often with methodological limitations, alongside extensive preclinical research and traditional use. This grade suggests some promising signals but indicates a need for more robust human data to confirm efficacy.

Filter by source type

Meta-Analyses(1)

Pooled analyses across multiple human trials.

Very High Quality
  • Administration of silymarin in NAFLD/NASH: A systematic review and meta-analysis.

    Li S, Duan F, Li S, Lu B · Annals of hepatology · 2024 · n=375

    Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease with a high prevalence worldwide and poses serious harm to human health. There is growing evidence suggesting that the administration of specific supplements or nutrients may slow NAFLD progression. Silymarin is a hepatoprotective extract of milk thistle, but its efficacy in NAFLD remains unclear. Relevant studies were searched in PubMed, Embase, the Cochrane Library, Web of Science, clinicaltrails.gov, and China National Knowledge Infrastructure and were screened according to the eligibility criteria. Data were analyzed using Revman 5.3. Continuous values and dichotomous values were pooled using the standard mean difference (SMD) and odds ratio (OR). Heterogeneity was evaluated using the Cochran's Q test (I2 statistic). A P<0.05 was considered statistically significant. A total of 26 randomized controlled trials involving 2,375 patients were included in this study. Administration of silymarin significantly reduce

    Meta-AnalysisPubMedVery High Quality

Observational Studies(3)

Cohort, case-control, and cross-sectional human studies.

Moderate Quality
  • Medicinal Plants in Food Supplements for Gastrointestinal Disorders: Critical Assessment of Health Claims on Gastric Acid Regulation.

    Teterovska R, Skotele RE, Maurina B, Sile I · Nutrients · 2025

    Gastrointestinal (GI) disorders associated with increased gastric acid secretion, such as gastroesophageal reflux, dyspepsia, bloating, and abdominal pain, significantly impair quality of life and present a substantial healthcare burden. Conventional therapies may have limited efficacy or undesirable side effects, underscoring the need for safe complementary approaches. This study systematically identifies and reviews the medicinal plants used in food supplements (FSs) marketed in Latvia for digestive health, focusing on the conditions linked to excess gastric acid. A structured literature search was conducted to identify European plant species with proven protective effects on the digestive system or the ability to influence gastric acid levels. A market analysis was performed using the Latvian Food and Veterinary Service FS Register. A total of 218 FS-containing medicinal plants were identified, of which 15 species were included in at least ten products. The most frequently used pl

    Observational StudyPubMedLow Quality
  • A review on the mechanisms of the effect of silymarin in milk thistle (Silybum marianum) on some laboratory animals.

    Khazaei R, Seidavi A, Bouyeh M · Veterinary medicine and science · 2022

    One of the most valuable medicinal plants is milk thistle (Silybum marianum) or martighal. An annual or biennial plant of the Asteraceae family and English name Milk thistle, a Matte green colour and prickly plant with a standing stem that can be thick, simple, or slightly branched (ramified). Its seeds contain about 70%-80% of the flavonolignans of silymarin and about 20%-30% of polymeric and oxidized polyphenolic compounds (such as tannins). Traditionally, the plant has been used to increase milk secretion, relieve menstrual cramps, lessen depression, decrease gallstones, and jaundice as well as improve functions of the liver, spleen, and kidney. This review reviews studies on the effects of adding milk thistle to quail diet. Consumption (0.5% and 1%) of milk thistle powder in the diet of Japanese quail significantly increased feed intake, body weight, and improved carcass components. Blood constituents including total protein and albumin were improved along with decreased HDL, ALT,

    Observational StudyPubMedLow Quality
  • Phytotherapy and NAFLD--from goals and challenges to clinical practice.

    Milosević N, Milanović M, Abenavoli L, Milić N · Reviews on recent clinical trials · 2014

    Non-alcoholic fatty liver disease (NAFLD) is a global problem and one of the most common liver diseases in the world. Various pharmacological and non-pharmacological therapies seem to be non-effective and the patients are often advised not to expect a positive outcome. Hence, even in the modern Western society many patients reach for traditional herbal products. Silymarin, a lipophilic extract derived from milk thistle (Silybum marianum) has been used in liver and bile disorders for centuries. Strong antifibrotic, antioxidant, antiviral and anti-inflammatory activities of silymarin joined with its metabolic effect proven in vitro make it ideal as a drug candidate in the therapy of NAFLD. Several recent randomized clinical studies have demonstrated that silymarin versus placebo significantly contributes to amelioration of the liver condition affected by NAFLD since it reduces steatosis severity, liver ballooning and fibrosis, followed by lowered aminotransferase levels in both short and

    Observational StudyPubMedLow Quality

Government Health Sources(1)

Public-health agencies: NCCIH, NIH, CDC, NHS.

High Quality
  • Milk Thistle

    NCCIH

    This NCCIH page provides general information on milk thistle, including its uses, potential side effects, and what the science says about its effectiveness for various conditions. It does not specifically address estrogen dominance but offers a foundational overview of the herb.

    Government SourceNCCIHHigh Quality

Clinical Trial Registries(2)

Registered ongoing or completed trials (ClinicalTrials.gov).

Moderate Quality
  • N-Acetylcysteine and Milk Thistle for Treatment of Diabetic Nephropathy.

    n=114 · NCT00915200 · COMPLETED · COMPLETED

    The study is designed to test if the combination of two potent antioxidant nutritional supplements, N-acetylcysteine and the milk thistle extract silibin, is capable of correcting the shedding of urine protein, the oxidative stress, and the inflammation in patients with type 2 diabetes mellitus and diabetic kidney disease.

    Clinical TrialClinicalTrials.govModerate Quality
  • Effect of Over-the-counter Dietary Supplements on Kidney Stone Risk

    n=45 · NCT02404701 · COMPLETED · COMPLETED

    The purpose of this study is to ascertain whether certain supplements promote excessive urinary oxalate excretion and increase the risk for calcium oxalate kidney stones. Supplements that enhance urinary oxalate excretion, as a result of their oxalate concentration or from some other mechanism (e.g., providing substrate for oxalate biosynthesis) will be identified by the investigators.

    Clinical TrialClinicalTrials.govModerate Quality

Evidence Summaries(1)

Curated cross-source summaries (TRIP Database and similar).

High Quality
  • Milk Thistle (Silybum marianum)

    Natural Medicines Database

    The Natural Medicines Database provides a comprehensive professional monograph on milk thistle, covering its clinical effectiveness, adverse effects, and drug interactions. It serves as a detailed reference for healthcare professionals regarding herbal supplements, though specific guidance on estrogen dominance may require deeper exploration within the database.

    Evidence SummaryNatural Medicines DatabaseHigh Quality

Limitations: Current evidence is limited by heterogeneity in study designs, small sample sizes in many human trials, and variability in milk thistle preparations and dosages used. Many studies are older, and some have relied heavily on surrogate markers rather than clinical outcomes, making definitive conclusions challenging.

This page is educational. Statements use phrases like "may support" and "has been studied for"because no remedy here is approved to cure, treat, or reverse any condition. Discussion happens on the ailment pages — community statistics here are derived from those reports. Always consult a qualified clinician.

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