New evidence
Thistle extract cut a key liver enzyme by a wide margin in a meta-analysis of 2,283 NAFLD patients — but came with a catch.
This meta-analysis offers the first solid evidence that silymarin from thistle can sharply reduce AST levels in people with fatty liver disease, but the moderate strength of the evidence (8 studies, 5 beneficial) and the risk of gastrointestinal side effects mean the picture is promising, not proven.
Researchers pooled data from 2,283 people with nonalcoholic fatty liver disease and found that thistle extract (silymarin) significantly lowered aspartate aminotransferase (AST), a marker of liver injury. The effect was large, but the same analysis also found it increased the risk of stomach-related side effects, and the result comes from a limited set of studies that haven't been fully replicated.
Where this fits in the evidence
Pillser has synthesized 8 studies on Thistle for Reduced Aspartate Aminotransferase Level — overall evidence strength: Moderate.
Across 8 studies, 5 reported beneficial effects of thistle (silymarin) on reducing aspartate aminotransferase (AST) levels, with effect sizes ranging from small to large (predominantly large). The evidence is strongest in clinical populations with liver conditions (NAFLD, ALD, hepatitis) and metabolic syndrome, with effects typically observed at 12 weeks or longer. Doses ranged from 420 mg/day (140 mg three times daily) to 800 mg/day, though many studies did not specify dosing.
The study
- Meta-Analysis
- n = 2,283
- 2025-08-01
- Asia Pacific journal of clinical nutrition
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