Quercetin #research Based on animal studies involving oral quercetin application some possible critical safety aspects could be identified such as the potential of quercetin to enhance nephrotoxic effects in the predamaged kidney or to promote tumor development especially in estrogen-dependent cancer. Source: [Safety Aspects of the Use of Quercetin as a Dietary Supplement - PubMed](https://pubmed.ncbi.nlm.nih.gov/29127724/) [Dietary quercetin exacerbates the development of estrogen-induced breast tumors in female ACI rats - PubMed](https://pubmed.ncbi.nlm.nih.gov/20600213/)