Across 3 studies, 2 reported beneficial effects (one moderate, one small) of red grape or its constituents (flavonoids, grape seed extract) on reducing ALT levels, primarily in individuals with NAFLD. The median study duration was 60 days (reported in one study). Evidence is preliminary, with effect sizes ranging from small to moderate.
Caveats: Evidence base is small (only 3 studies) — conclusions should be considered preliminary. Only one study reported dosage and duration (grape seed extract 520 mg/day for 60 days); effects may depend on form and duration. The neutral study was in transfusion-dependent thalassemia patients, a different clinical context, so benefit may be specific to NAFLD.
Flavonoids intervention significantly decreased ... alanine aminotransferase (ALT)
insulin, HOMA-IR, TC, TG, LDL-c, ALT, AST, AST/ALT, SBP, DBP and MAP decreased and QUICKi and HDL-c increased significantly (p-value for all < 0.05)
In contrast, quercetin and curcumin supplementation did not show a statistically significant difference compared to control groups in these outcomes.