Milk Thistle (Silymarin)

We evaluated 212 human studies on Milk Thistle (Silymarin), including 56 randomised controlled trials and 42 meta-analyses or systematic reviews; the controlled studies include 3,909 participants in total. As of 7 October 2026.

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1. What Is Milk Thistle (Silymarin)? Occurrence, Origin and Forms

Milk thistle (Silybum marianum) is a thistle-like plant in the daisy family. Its ripe fruits yield the extract silymarin, a mixture of flavonolignans. Traditionally the plant is used for upper abdominal complaints and in connection with the liver.

Milk thistle grows in dry, sunny locations and is cultivated for its fruits. The ripe fruits are the part used, and the extract is made from them.

For the extract, the ripe fruits are harvested and extracted with solvents; the result is adjusted to a defined silymarin content. Studies examine, among other things, standardized silymarin extracts, the single compound silibinin, a complex of silymarin and phosphatidylcholine, and silibinin-containing infusion solutions.

Forms and Preparations Studied

• Whole or ground fruits (tea, powder)
• Standardized silymarin extract
• Silibinin (silybin) as a single compound
• Silymarin–phosphatidylcholine complex
• Silibinin infusion solution
• Other flavonolignans such as silychristin and silydianin

Not covered on this page:

• Other liver plants such as artichoke, dandelion and greater celandine
• Milk thistle seed oil pressed from the seeds, which is not obtained through silymarin extraction
• Combination products in which silymarin appears alongside other substances
• Silibinin as a laboratory reagent in cell experiments without reference to use in humans

2. What Does Milk Thistle (Silymarin) Do? Results by Area

How to read the table: counted are human studies whose results concern the area. “High” means at least one meta-analysis and two controlled studies showing improvement, or at least three controlled studies of which three quarters show improvement, with at least 300 participants in total. “Moderate” means at least two controlled studies showing improvement, as a majority, or one meta-analysis alongside controlled studies. “Low” means one controlled study showing improvement. Where an area has no controlled study, the strength of evidence is at most “low” (result “reviews only” or “observational data only”). Everything else is “unclear”. A study counts as showing improvement when at least half of its outcomes in this area improved. Reviews of combination products do not count as meta-analyses; results that only describe side effects or shares of users do not count as an effect. The same study is counted only once.

3. What the Studies Show in Detail

Milk Thistle (Silymarin) and Liver Values During Drug Treatment: Human Studies

During treatment with tuberculosis drugs, silymarin in a meta-analysis of placebo-controlled studies preventively reduced the risk of liver damage as well as ALT, AST and ALP 15. A small randomized study confirmed lower AST and ALP values after two weeks 74. For drug-induced liver injury overall, however, a larger meta-analysis found no confirmed effect 3. In children undergoing chemotherapy, a traditional fruit infusion lowered ALT more than silymarin 52. Compared with placebo, controlled studies under chemotherapy found more favorable ALP and bilirubin values 47 and less liver fat accumulation on ultrasound 95, and under fingolimod lower ALT and AST 70. In children with leukemia undergoing maintenance therapy, ALT, AST, GGT and bilirubin decreased slightly more than under placebo 45.

Further studies in this area: 38 40 41 45 47 70 74 77 95 103 105 134 138 157 158 163 165 178 182 185

Milk Thistle (Silymarin) and Non-Alcoholic Fatty Liver Disease: Human Studies

In non-alcoholic fatty liver, silymarin lowered ALT and AST compared with control in meta-analyses 3433. A meta-analysis also found lower blood lipids and less fat in liver tissue 4. In a placebo-controlled study, by contrast, only GGT and liver stiffness decreased, not the transaminases 51. Compared with essential phospholipids, silymarin performed worse for cholesterol, while liver values and fat did not differ 49. A randomized study found a better ultrasound classification, but no difference in the NAFLD score 67. A randomized controlled study on the silymarin extract Legalon® found no histological improvement in NASH 56. Combinations with diet, lifestyle change or medications lowered transaminases in a meta-analysis; this applies only to the respective combination 5. A Cochrane review rates the ALT reduction by silymarin alone as very uncertain 6. The results are based mainly on blood values; preparations, doses and comparison groups differ greatly, and an improvement of inflammation in liver tissue in NASH has not been demonstrated.

Further studies in this area: 18 30 33 49 51 56 66 67 90 92 99 100 104 118 132 133 135 143 148 149 150 152 155 158 159 160 161 169 177 178 182

Milk Thistle (Silymarin), Diabetes and Blood Glucose: Human Studies

For diabetes and blood sugar, meta-analyses on silymarin show predominantly favorable effects on blood sugar, fasting insulin and HbA1c. A meta-analysis of controlled studies found lower fasting blood sugar, fasting insulin and HbA1c 7, and a meta-analysis on fatty liver found lower fasting insulin 4. A systematic review on silibinin relies predominantly on cell and animal studies 30. This contrasts with a controlled study in diabetes in which a standardized extract over twelve weeks did not change fasting blood sugar, HbA1c and blood lipids 69. Mixtures with berberine 2223 or with nettle and frankincense 64 lowered fasting blood sugar compared with placebo; this applies only to the respective mixture. The meta-analyses 47 are especially robust; preparations and doses differ, and the transferability to individual milk thistle products remains open.

Further studies in this area: 91 140 145 153 155 170 173 174 178 183 184 188

Milk Thistle (Silymarin) and Chronic Hepatitis: Human Studies

In chronic hepatitis, a meta-analysis showed that a standardized silymarin extract improved liver enzymes in viral hepatitis 3. A controlled study (not randomized) found a greater ALT and AST reduction with silymarin tablets plus standard therapy than with standard therapy alone 90. In hepatitis C, silymarin performed equal to spirulina for viral response and worse for ALT reduction in a randomized study 59. The findings are thus based on one meta-analysis and two controlled studies with different preparations and endpoints. For chronic hepatitis C, there is therefore no clear advantage of silymarin over other approaches; for chronic hepatitis B and other etiologies, the data situation is inconsistent.

Milk Thistle (Silymarin) and Liver Cirrhosis: Human Studies

In liver cirrhosis, a systematic review found lower AST and ALT values in three of six silymarin studies; side effects were rare 19. A non-randomized controlled study in chronic liver diseases of various causes found no difference in encephalopathy, ascites, CTP class, and FibroScan values in addition to standard therapy 90. It remains open whether standardized extract has a clinically relevant benefit in cirrhosis; the forms studied were standardized silymarin extract, silymarin without further specification, and silibinin.

Further studies in this area: 182

Milk Thistle (Silymarin) and Cancer (Silibinin): Human Studies

On the effect on cancer diseases themselves, only observational data and reviews are available; the strength of evidence is low. A case series reports better tolerability, quality of life and fewer neurological symptoms with silibinin in addition to standard therapy 108. An observational study found better response with a silibinin-containing dietary supplement in addition to chemotherapy in lung cancer, but no confirmed survival benefit 109. An observational study on silymarin in addition to antiviral therapy found no difference in the incidence of liver cancer 101. Review articles on silymarin and silibinin in gastrointestinal tumors rely predominantly on preclinical findings 172173. The standardized extract, silibinin as a single substance, the silybin-phosphatidylcholine complex as well as unspecified milk thistle preparations were studied; data on whole fruits or tea are lacking in this area.

Further studies in this area: 154 172 173

Milk Thistle (Silymarin) and Death Cap Mushroom Poisoning: Human Studies

On death cap mushroom poisoning, no controlled studies are available; the assessment is based on observational data and review articles. A systematic evaluation of case reports found higher survival rates with silibinin or penicillin alone as well as with combinations with N-acetylcysteine than with purely supportive treatment 16. In confirmed poisoning, the differences were not significant 16. An observational study with oral silymarin found no differences in hospital mortality, acute liver failure, and hospital length of stay 102. A case series with silibinin infusion and penicillin describes less treatment failure with the combination than with silibinin alone 106. A single-arm study with silibinin infusion, fluid administration, and octreotide reports frequent recovery without transplantation; silibinin predicted survival, N-acetylcysteine and activated charcoal did not 107. A review article considers the benefit in liver diseases including mushroom poisoning as not yet proven despite encouraging preclinical data 182. Since the data come predominantly from uncontrolled observations and the preparations examined — silibinin infusion, oral extract, combinations — are not comparable, no reliable statement can be derived from them.

Further studies in this area: 168 182

Milk Thistle (Silymarin): Further Outcomes in Studies

In this area, very different endpoints were examined, predominantly with standardized silymarin extract, and additionally with silibinin as a single substance, nanomicelles, cream, and combination preparations. Controlled studies found less oxidative stress with silymarin 7072, a lower CRP after bypass surgery 89, and more HDL and fewer triglycerides 72. In emergency patients with oxygen deficiency, silymarin lowered liver enzymes more than placebo 88. A randomized split-face study in melasma found fewer side effects with silymarin cream than with hydroquinone and no confirmed difference in lightening 78. Many results in this area are based on small, partly non-randomized studies. Mixtures with berberine lowered blood lipids in meta-analyses; this cannot be attributed to silymarin alone 2223. A systematic review on antioxidants in melasma describes silymarin as effective with few side effects 26. Forms examined were standardized extract, silibinin, and topical and nanomicellar preparations.

Further studies in this area: 22 23 24 25 26 27 28 29 30 31 34 35 36 37 39 40 42 43 47 50 51 53 55 56 58 60 61 62 63 65 66 67 69 70 71 72 73 75 76 78 79 80 81 82 83 84 86 87 88 89 90 93 94 96 97 98 101 107 110 111 112 113 114 115 116 117 118 120 121 123 124 125 128 129 130 136 137 139 140 141 142 147 151 153 156 162 163 164 166 167 170 171 173 174 175 176 179 180 181 182 183 184 185 186 187 189

4. How Is Milk Thistle (Silymarin) Dosed? Preparation, Dose and Duration in Studies

The studies predominantly tested standardized silymarin extracts (partly as named commercial preparations, partly nanomicellar or as a cream) as well as silibinin as a single substance, alongside milk thistle fruit powder extract and the silybin-phosphatidylcholine complex. Larger controlled studies on whole or ground fruits (tea, powder) are lacking; individual topicals used milk thistle ointment without a further specified extract. Strikingly many studies examined combination preparations in which silymarin was combined with other components; their results apply only to the respective mixture, not to silymarin alone.

5. Is Milk Thistle (Silymarin) Safe? Side Effects in Studies

The tolerability of silymarin is predominantly described as good; mostly only mild complaints such as gastrointestinal reactions or insomnia were reported 1419354347. A meta-analysis on fatty liver found adverse effects more frequently under silymarin, especially gastrointestinal complaints 5. A possible bleeding risk with simultaneous intake of anticoagulants is also reported 39.

6. What Remains Open: Limits of the Evidence

• The tested preparations (standardized extract, silibinin, complex, commercial preparations) and doses differ greatly, so results cannot be transferred to all products.
• Controlled studies in humans are lacking for whole or ground fruits (tea, powder) and for milk thistle seed oil.
• An improvement of inflammation in liver tissue in NASH is not proven 56; many endpoints are based only on blood values or ultrasound.
• Many results on combination preparations cannot be attributed to silymarin alone because other components were also studied.
• For several areas (mushroom poisoning, cancer), the data come predominantly from uncontrolled observations.

7. Bottom Line: What Is Established About Milk Thistle (Silymarin)

Milk thistle (Silybum marianum) provides with silymarin a mixture of flavonolignans that has been tested in many studies in humans. Liver values are best studied: meta-analyses found lower transaminases in fatty liver and viral hepatitis 34, and less frequent liver damage under tuberculosis drugs 15. In diabetes, silymarin lowered fasting blood glucose, insulin and HbA1c in a meta-analysis 7, while a controlled single study found no difference 69. Liver tissue in NASH did not improve in a placebo-controlled study 56.

Many investigations also used combination preparations whose results apply only to the respective combination. Tolerability is mostly described as good; a meta-analysis found adverse effects more frequently, especially gastrointestinal complaints 5, and a bleeding risk is described under anticoagulants 39.