The preclinical safety study in mice, published in Phytotherapy Research, delivered toxicology data for Kerry’s Sensoril ingredient—a 1:1 root and leaf aqueous extract—at up to 19 times the standard dose.
“This is the first time an OECD-compliant pre-clinical toxicology study has been conducted on an ashwagandha root and leaf extract,” said Dr. Mukesh Summan, global director of toxicology at Kerry Group and lead author of the study. “This study will help to reassure regulators on ashwagandha’s toxicological profile and address a pre-existing gap in the literature.”
Increasing caution over leaf extract
The research comes amidst a backdrop of increasing caution over the botanical across Europe and India, including a ban in Denmark, a proposed ban in the Netherlands, an ongoing Food Standards Agency (FSA) review in the UK, and a newly placed ban of the leaf extract in India.
The ashwagandha root is more expensive and has been touted as the superior and recommended part of the plant for use in dietary supplements due to its history of safe use, extensive clinical research, and withanolide balance.
Some have raised concerns about the higher levels of Withaferin A in ashwagandha leaves, a compound with cytotoxic (cell-killing) effects. Traditionally, the leaves have primarily been used in topical treatments but today many ingestible supplements include leaf extract.
Dr Thomas Brendler, founder of Plantifile, has devoted significant time to compiling and assessing a series of papers on ashwagandha for publication in Phytotherapy Research, and found no evidence to suggest ashwagandha leaf pose any safety or efficacy concerns.
“Both root and leaf have been studied for similar, if not the same, effects and we found there is no obvious difference in efficacy or safety or leaf products or root products or combination of root and leaf,” he revealed in a recent Kerry podcast.
Yet, earlier this month the Food Safety and Standards Authority of India (FSSAI) along with the Ministry of AYUSH prohibited the use of ashwagandha leaves in food products and nutraceuticals, while continuing to allow the use of the plant’s root.
Dr. Summan said Kerry is actively engaging with Indian regulators and relevant industry stakeholders to provide scientific evidence and to seek clarification and, reconsideration of the position on leaf use.
“Ashwagandha leaf has a long history of use and is cited in classical Ayurvedic texts. It is our view that the recommendation does not fully reflect the weight of scientific evidence or ancient texts pointing to the safety of the overall plant,” he said.
Study details
The potential for Sensoril to cause toxicity other than genotoxicity was evaluated in a 90- day repeat dose oral toxicity study in four groups of 20 rats (10 male and 10 female).
Sensoril was administered at dose levels of 1000, 2000, and 4000 mg/kg BW/day by oral gavage daily for 90 days—19 times higher than the standard Sensoril dose of 125mg.
Rats underwent detailed clinical observations weekly throughout the treatment and the four week recovery period, with ophthalmology, urinalysis, functional, and neurobehavioral tests performed prior to scheduled necropsy.
Following completion of the treatment, blood samples were collected and full examination of body tissues were conducted post euthanasia.
Resulting data indicated no mortality, morbidity, adverse clinical signs or toxicologically relevant changes over 90 days. It provided full genotoxicity clearance across three OECD-compliant tests: the Ames assay, in vitro Micronucleus assay, and Mammalian Bone Marrow Chromosome Aberration test.
In total, Kerry has completed 15 gold-standard clinical trials and various preclinical studies into its ashwagandha extract which identify no adverse effects or safety concern.
Source: Phytotherapy Research, https://doi.org/10.1002/ptr.70314, “Safety Evaluation of an Aqueous Root and Leaf Extract of Ashwagandha (Withania somnifera)”, Authors: Summan, M., et al
