Plant Part-Specific Differences in Ashwagandha (Withania somnifera): A Comparative Evaluation of Root and Leaf Evidence for Safety and Regulation.

Ashwagandha (Withania somnifera) is a key herbal product traditionally used as a root-based rejuvenative. Leaf and whole-plant preparations have also become increasingly available, for which dedicated safety characterization remains limited. European risk assessments and the Danish ban have raised safety concerns for "ashwagandha" without consistently distinguishing plant parts. We conducted a structured narrative review with a regulatory focus, integrating traditional sources, phytochemical and pharmacologic studies, human clinical trials, pharmacovigilance data, quality/adulteration investigations, and national and international risk assessments. Electronic databases and gray literature sources (including AYUSH, DTU, RIVM, and FSA) were searched through 31 March 2026, and evidence was synthesized qualitatively along the axes of traditional use, phytochemistry, efficacy, safety, quality and regulation, explicitly contrasting root and leaf. Root consistently shows a profile dominated by withanolide A, D, and glycol-withanolides, whereas leaf is richer in withaferin A and related electrophilic withanolides. Multiple randomized controlled trials and a 12-month study of standardized root extracts demonstrate clinically relevant reductions in stress, anxiety, and insomnia, with generally favorable safety and no reproducible serious organ toxicity. Human data for leaf are sparse and confounded, while preclinical leaf studies emphasize the high withaferin A content and anticancer and immunomodulatory effects and theoretical toxicity concerns. European risk opinions have extrapolated mixed plant-part data to all ashwagandha preparations, even as analytical surveys document adulteration of root materials with leaves and stems. Current evidence supports greater confidence in authenticated, standardized root preparations for systemic use, while evidence for leaf remains limited and requires indication-specific development and dedicated safety evaluation. These findings support plant-part specificity in regulatory frameworks, including analytical authentication to detect leaf adulteration, plant-part- and product-specific risk assessment, and re-assessment of plant-part-agnostic safety conclusions as higher-quality evidence emerges. Future research should prioritize comparative trials of root versus leaf and whole-plant extracts and long-term safety studies of standardized leaf preparations.