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Evidence-Based Supplement Research
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Red Grape

What does the research say about Red Grape?

4 health outcomes synthesised

Research on Red Grape extract has investigated its effects on 4 health outcomes, with the strongest evidence supporting a reduction in diastolic blood pressure based on 4 studies showing consistent beneficial effects. The most commonly studied dose is 520 mg/day of grape seed extract, primarily in populations with hypertension or metabolic syndrome. Other outcomes show moderate evidence for liver enzyme reduction, but overall findings are preliminary due to small study sizes and limited generalizability.

Strongest evidence: The most consistent evidence for Red Grape extract, predominantly in the form of grape seed extract, is for reducing diastolic blood pressure. All 4 studies reported beneficial effects with small effect sizes, and the evidence strength is rated as moderate. Across these studies, a dose of 520 mg/day was used in one trial, and the median study duration was 34 days. Additionally, moderate evidence supports a reduction in aspartate aminotransferase (AST) levels: 3 of 4 studies (including one with 100 mg/day and one with 520 mg/day) showed benefit in clinical populations with NAFLD or β-thalassemia.

Mixed or weaker evidence: Evidence for reducing alanine aminotransferase (ALT) is moderate but mixed: 2 of 3 studies reported benefit (one moderate, one small effect), while one study in transfusion-dependent thalassemia patients was neutral. For systolic blood pressure, the evidence strength is low: only 2 of 4 studies showed small beneficial effects, and a meta-analysis reported high heterogeneity (I² = 97.4%) with no significant pooled effect. This suggests that the effect on systolic BP is inconsistent and may be smaller than the predominant direction indicates.

Effective dose patterns: Across outcomes, the most frequently reported effective dose is 520 mg/day of grape seed extract, which appeared in studies for diastolic BP, ALT, and systolic BP. For AST reduction, a lower dose of 100 mg/day was also effective in one study. However, many studies did not specify doses, and the evidence base is too small to determine a precise dose-response relationship.

Population insights: The majority of positive findings come from clinical populations with hypertension, metabolic syndrome, or non-alcoholic fatty liver disease (NAFLD). One study in β-thalassemia major patients also showed benefit for AST. Generalizability to healthy individuals or to other forms of red grape (e.g., whole grape, juice) is uncertain, as most studies used grape seed extract.

Notable caveats: All syntheses note that the evidence base is small (3–4 studies per outcome), making conclusions preliminary. Publication bias is a concern, as null results may be less likely to be published. Additionally, the studies used various forms of red grape (primarily seed extract), so effects may not apply to other preparations. The short study durations (median 34 days for BP outcomes) limit long-term conclusions.

Frequently asked

  • What is Red Grape good for according to research?
    Research indicates that red grape extract, particularly grape seed extract, may help reduce diastolic blood pressure and lower certain liver enzymes (AST and ALT) in specific populations. However, the evidence is moderate and preliminary, with only 4 studies per outcome for blood pressure and liver enzymes. Effects on systolic blood pressure are less consistent.
  • What dose of Red Grape is typically used in studies?
    The most commonly studied dose is 520 mg/day of grape seed extract, used in trials for diastolic blood pressure, ALT, and systolic blood pressure. For AST reduction, a dose of 100 mg/day was also effective in one study. Doses were not specified in all studies, and the optimal dose remains unclear.
  • Who benefits most from Red Grape?
    Beneficial effects have been observed primarily in people with hypertension or metabolic syndrome (for blood pressure) and in individuals with NAFLD or β-thalassemia major (for liver enzymes). These findings may not generalize to healthy individuals or to those without these conditions.
  • Are there caveats or limitations in the research on Red Grape?
    Yes, the evidence base is small, with only 3–4 studies per outcome, and conclusions are preliminary. Most studies used grape seed extract rather than whole grape products, so results may not apply to other forms. Publication bias is a concern, and many studies had short durations (1–2 months).
  • Does Red Grape help with diastolic blood pressure?
    All 4 studies on diastolic blood pressure reported beneficial effects, with small effect sizes and moderate evidence strength. The most common dose was 520 mg/day of grape seed extract, and the studies involved populations with hypertension or metabolic syndrome. However, the evidence is preliminary due to the small number of studies.
  • Does Red Grape help with liver enzymes?
    Moderate evidence suggests that red grape extract may reduce AST and ALT levels in people with NAFLD. For AST, 3 of 4 studies were beneficial; for ALT, 2 of 3 studies showed benefit. However, one neutral study for each outcome involved different populations (β-thalassemia or transfusion-dependent thalassemia), indicating that effects may be condition-specific.

Most-studied combinations with Red Grape

most supplement research is combination research
Also studied with:Turmeric (2), Ginkgo (2), Thistle (2)
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