GradedHealth

Does milk thistle help your liver? What the trials show

Pooled trials link milk thistle to lower liver enzymes in fatty liver. Larger trials in hepatitis C found no clear liver benefit.

Published October 2026

Short answer

Early, mixed evidence: milk thistle may lower liver enzymes in fatty liver, but it has not clearly protected the liver or prolonged life in larger trials. Evidence grade C (Limited). Meta-analyses of trials, downgraded for inconsistency (some trials and reviews show no change) and for relying on liver enzymes and scans rather than clinical outcomes.

Key takeaways

  • Across 26 trials with 2,375 people with fatty liver, silymarin lowered the liver enzymes ALT and AST [1][2].
  • In a 24-week trial of 83 people with fatty liver, silymarin lowered liver stiffness, a scan measure linked to scarring; two authors work for the institute named in its conflict-of-interest statement [3].
  • In 154 people with hepatitis C, silymarin did not lower ALT more than placebo [4].
  • Five small trials linked silymarin to lower fasting blood sugar and HbA1c, but a 12-week trial of 48 people found no change [5][6].
  • A 2007 Cochrane review of 18 trials found no clear effect on death in people with alcohol-related or hepatitis liver disease, and most trials were low quality [7].

The short version

Milk thistle may help fatty liver disease, at least on blood tests. Pooled trials found that its main extract, silymarin, lowers the liver enzymes ALT and AST [1][2]. Larger trials have not shown a clear protection of the liver itself, so the benefit is early and uncertain [4][7].

What the studies show

A review of 26 randomised trials with 2,375 people with fatty liver found that silymarin lowered ALT and AST compared with control [1]. A separate review of eight placebo-controlled trials reached the same result [2]. A larger review of 41 trials also reported lower ALT, AST and ALP, with the clearest liver effects in longer, higher-dose use [8].

In a 24-week trial of 83 people with fatty liver, silymarin lowered liver stiffness, a scan measure that tracks scarring, more than placebo [3].

In a 48-week trial of 99 people with the more severe NASH form of fatty liver, the share who cut their disease score by 30% or more did not differ from placebo (32.7% vs 26.0%). More people on silymarin had a one-point improvement in fibrosis on biopsy (22.4% vs 6.0%) [9].

A 12-month trial of 179 people with fatty liver used a silybin and phosphatidylcholine complex with vitamin E rather than standard silymarin. The people on it had better liver enzymes and liver biopsy scores than those on placebo [10].

Not every trial agrees. In 154 people with hepatitis C who had not responded to interferon, silymarin at 420 or 700 mg three times a day for 24 weeks did not lower ALT more than placebo [4]. A review of a berberine and silymarin combination also found no change in ALT or AST [11].

For blood sugar, five trials with 270 people with type 2 diabetes found lower fasting glucose and HbA1c, a three-month blood sugar average [5]. A 12-week trial of 48 people found no change in fasting glucose, HbA1c or lipids [6].

For survival, a 2007 Cochrane review of 18 trials with 1,088 people found no significant effect on death from alcohol-related or hepatitis B or C liver disease [7]. Only 28.6% of those trials used high-quality methods [7].

The nuances

The products differ. Silymarin is absorbed poorly at usual doses, and a phase I study suggests absorption improves above 700 mg a day [12]. Results from a silybin complex may not apply to a standard silymarin capsule [10].

Most trials were short, between 12 and 48 weeks [6][9], and small. Liver enzymes, scan stiffness and biopsy scores are markers, not outcomes like cirrhosis or death [3][9].

Some trials were linked to the supplement industry. One fatty liver trial had two authors employed by BYHEALTH Institute of Nutrition and Health [3].

Side effects were mild in trials. The NASH trial found no more adverse events than placebo [9], and a review lists nausea and diarrhoea [13].

Drug interactions are the main concern. A 2020 case report describes a man on warfarin whose INR, a blood-clotting test, rose from 2.64 to 4.12 while taking a supplement containing 200 mg of milk thistle. It returned to normal after he stopped [14]. A review says silymarin may affect some drug-processing enzymes, but that this is unlikely to matter in practice [15]. Another review advises caution with drugs that have a narrow safe range [13].

Pregnancy data are limited. One review notes a trial in pregnancy with no birth defects, but advises caution [13]. We found no studies on breastfeeding.

What this means for you

Milk thistle is not an established treatment for fatty liver or hepatitis. Blood-test changes in trials do not yet show better liver health or longer life [7][4]. If you have liver disease, take blood thinners or diabetes medicines, or are pregnant, talk to your doctor before taking it. The Milk Thistle topic page has the full safety information.

Go deeper

  • Milk Thistle — Milk thistle may lower liver enzymes in fatty liver disease in pooled trials, but larger trials have not shown clear protection of the liver or a lower risk of…

References

  1. Administration of silymarin in NAFLD/NASH: A systematic review and meta-analysis.. Ann Hepatol, 2024.
  2. Impact of Silymarin in individuals with nonalcoholic fatty liver disease: A systematic review and meta-analysis.. Nutrition, 2021.
  3. Silymarin decreases liver stiffness associated with gut microbiota in patients with metabolic dysfunction-associated steatotic liver disease: a randomized, double-blind, placebo-controlled trial.. Lipids Health Dis, 2024.
  4. Effect of silymarin (milk thistle) on liver disease in patients with chronic hepatitis C unsuccessfully treated with interferon therapy: a randomized controlled trial.. JAMA, 2012.
  5. Silymarin in Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.. J Diabetes Res, 2016.
  6. Effect of silymarin on lipid profile and glycemic control in patients with type 2 diabetes mellitus.. Phytother Res, 2024.
  7. Milk thistle for alcoholic and/or hepatitis B or C virus liver diseases.. Cochrane Database Syst Rev, 2007.
  8. Effects of silymarin supplementation on liver and kidney functions: A systematic review and dose-response meta-analysis.. Phytother Res, 2024.
  9. A Randomized Trial of Silymarin for the Treatment of Nonalcoholic Steatohepatitis.. Clin Gastroenterol Hepatol, 2017.
  10. Silybin combined with phosphatidylcholine and vitamin E in patients with nonalcoholic fatty liver disease: a randomized controlled trial.. Free Radic Biol Med, 2012.
  11. Effects berberine-silymarin on liver enzymes: A systematic review and meta-analysis of randomized controlled trials.. Clin Nutr ESPEN, 2022.
  12. Silymarin ascending multiple oral dosing phase I study in noncirrhotic patients with chronic hepatitis C.. J Clin Pharmacol, 2010.
  13. Safety and toxicity of silymarin, the major constituent of milk thistle extract: An updated review.. Phytother Res, 2019.
  14. CYP2C9-mediated warfarin and milk thistle interaction.. J Clin Pharm Ther, 2020.
  15. Metabolism, Transport and Drug-Drug Interactions of Silymarin.. Molecules, 2019.