Ashitaba: Is It Safe? Study Reveals Dosage Limits

Key Findings

This 2015 GLP-compliant toxicological study concluded that Ashitaba chalcone powder (containing 4-hydroxyderricin and xanthoangelol) is not genotoxic based on bacterial reverse mutation, chromosome aberration, and in vivo micronucleus assays. The no-observed-adverse-effect-level (NOAEL) was determined to be 300 mg/kg/day in both male and female Sprague Dawley rats. Higher doses (1000 mg/kg/day) caused rat-specific pathologies, including alpha 2-urinary globulin nephropathy in males and jejunal lymphangiectasia in both sexes, but these were deemed non-relevant to humans. Physiological effects on coagulation and plasma lipids were noted at 300–1000 mg/kg/day, aligning with Ashitaba’s known pharmacological activity.

Study Design

The study combined in vitro genotoxicity assays (bacterial reverse mutation, chromosome aberration) and an in vivo micronucleus test in mice with a 90-day subchronic oral toxicity study in Sprague Dawley rats. The chronic phase used 10 rats per sex per group (total n=80), administered doses of 0, 100, 300, or 1000 mg/kg/day. Duration: 90 days for the rat study, with genotoxicity tests conducted over shorter periods.

Dosage & Administration

Ashitaba yellow sap powder standardized to 8.45% chalcones was administered via oral gavage at doses of 100, 300, or 1000 mg/kg/day. Control groups received vehicle-only treatments. Dosing frequency: daily for 90 days in rats; single doses for genotoxicity assays.

Results & Efficacy

• Genotoxicity: All assays (Ames test, chromosome aberration, micronucleus) showed no mutagenic or clastogenic effects.
• 90-day study:
• Coagulation: Dose-dependent increases in prothrombin time (PT) and activated partial thromboplastin time (aPTT) at 300–1000 mg/kg/day, consistent with Ashitaba’s anticoagulant properties.
• Plasma lipids: Reduced triglycerides and cholesterol at 300–1000 mg/kg/day (quantitative data unspecified).
• Pathology:
  • Alpha 2u-globulin nephropathy in male rats at all doses (p < 0.05 vs. control).
  • Jejunal lymphangiectasia in both sexes at 1000 mg/kg/day (p < 0.05).
• No other toxicologically significant changes in body weight, organ weights, or histopathology.

Limitations

• Species-specific pathology: Alpha 2u-globulin nephropathy is a rat-specific condition unrelated to human toxicity, limiting clinical applicability.
• Funding source: Conducted by a supplement manufacturer (Kaneka Corporation), potentially introducing bias.
• Sample size: Small group sizes (n=10/sex/dose) may reduce sensitivity to detect rare effects.
• Lack of mechanistic data: No detailed analysis of how chalcones influence coagulation or lipid parameters.
• Short duration: 90-day exposure does not assess long-term risks of chronic supplementation.

Clinical Relevance

For supplement users, this study supports the safety of Ashitaba chalcone powder at doses ≤300 mg/kg/day (equivalent to ~24g/day in humans based on body surface area scaling). The observed anticoagulant and lipid-lowering effects align with its traditional use but warrant caution in individuals on blood-thinning medications. The rat-specific kidney pathology suggests high doses (1000 mg/kg/day) may pose risks in rodents but not necessarily humans. Users should prioritize standardized products with defined chalcone content and avoid exceeding NOAEL-equivalent dosages until further human safety trials are conducted.

Note: This review lacks p-values or confidence intervals for most quantitative outcomes, relying on the authors’ qualitative assessment of significance. Future research should validate findings in human trials and explore long-term safety.