Across 10 studies, 6 reported beneficial effects of thistle (silymarin) on reducing aspartate aminotransferase (AST) levels, with 4 neutral findings and no harmful effects. Predominant effect sizes were mixed (small to large), with meta-analyses showing moderate-to-large reductions (SMDs ranging from -0.14 to -2.68). Effects were observed primarily in clinical populations, with a median study duration of 63 days (about 9 weeks), and a commonly reported dose was 420 mg/day of silymarin.
Caveats: Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed). Many studies did not specify the form of thistle used, and effect sizes varied from small to large, making the magnitude of effect uncertain. Several neutral findings came from smaller or shorter trials, and benefit may not extend to healthy adults without liver stress.
The silymarin use increased the rate of patients with adverse effects [RR:1.11, 3.54]
from: Efficacy of different interventions for nonalcoholic fatty liver disease: A meta-analysisThe evidence is very uncertain about the effect of silymarin monotherapy versus no intervention or placebo on non-serious adverse events (RR 1.29, 95% CI 0.88 to 1.89; 4 trials, 282 participants; very low-certainty evidence).
from: Silymarin for adults with metabolic dysfunction-associated steatotic liver disease.The evidence suggests that silymarin monotherapy versus no intervention or placebo may result in little to no difference in serious adverse events (Peto OR 1.55, 95% CI 0.26 to 9.28; 4 trials, 304 participants; low-certainty evidence).
from: Silymarin for adults with metabolic dysfunction-associated steatotic liver disease.No adverse effects were found in volunteers using silymarin (0.8 g/day), silymarin+yacon (0.8+2.4 g/day) and silymarin+maca (0.6+0.2 g/day).
from: Maca (Lepidium meyenii) and yacon (Smallanthus sonchifolius) in combination with silymarinNo adverse events were noted and both silymarin and placebo were well tolerated.
from: A randomized controlled trial to assess the safety and efficacy of silymarin on symptoms,Although one trial reported the occurrence of serious adverse events, none were deemed to be related to the study drugs.
from: Silymarin for adults with metabolic dysfunction-associated steatotic liver disease.gastrointestinal problems were the most common adverse effects.
from: Efficacy of different interventions for nonalcoholic fatty liver disease: A meta-analysisSilibinin capsules exhibited a favorable safety profile, with only mild gastrointestinal reactions and reports of insomnia as adverse events.
from: Evidence construction of Silibinin capsules against alcoholic liver disease based on a metSilibinin capsules exhibited a favorable safety profile, with only mild gastrointestinal reactions and reports of insomnia as adverse events.
from: Evidence construction of Silibinin capsules against alcoholic liver disease based on a metor medications [SMD: -1.41 (-2.24, -0.59), p=0.005].
Silymarin complex versus no intervention or placebo ... AST (MD 0.84 U/L, 95% CI -1.03 to 2.71; 4 trials, 309 participants; very low-certainty evidence)
[SMD =-0.14, 95% CI (-0.23, -0.06), P = 0.001(AST)]
AST [SMD = -1.56, 95% CI (-2.18, -0.95)]
the serum levels of aspartate aminotransferase (p = 0.015) ... at 6-week intervals ... were significantly lower in the silymarin group.
other variables including direct bilirubin, ALT and aspartate aminotransferase (AST) were not significantly reduced
No adverse effects were found in volunteers using silymarin (0.8 g/day), silymarin+yacon (0.8+2.4 g/day) and silymarin+maca (0.6+0.2 g/day). A moderate AST level and diastolic blood pressure increase was found in volunteers using maca (0.6 g/day).
Mean improvements in ALT, AST, ALP, and GGT were significantly greater with the nutraceutical product than placebo (p ≤ 0.001).
silymarin had the highest effect on the reduction of AST (SMD = -2.68)
In contrast, quercetin and curcumin supplementation did not show a statistically significant difference compared to control groups in these outcomes.