New Ginkgo-Cancer Analysis, Same Criticized Extract

RESEARCH TRIANGLE PARK, NCResearchers from National Institute of Environmental Health Sciences and National Toxicology Program(NTP) analyzed data from a two-year study of cancer in mice given Ginkgo biloba, finding complex mechanisms for hepatocarcinogenesis. The study was published in the August 2013 issue of Toxicologic Pathology (41(6): 826-841). Botanical experts, however, continue to note the ginkgo used in the study, which was featured in an NTP Tech Report earlier this year, is not the same as the ginkgo used in commercial preparation found in dietary supplements for human consumption.

In the, "NTP Technical Report on the Toxicology and Carcinogenesis Studies of Ginkgo biloba Extract in Rats and Mice," several of NTP's peer-reviewers cautioned against applying the results and conclusions of the two-year mice study to humans. One such reviewer, Ashley Roberts, Ph.D., senior VP of the Food & Nutrition Group at Intertek Cantox, expressed several concerns, including the stability of the dosing formulation. He explained the rat population used is known to have spontaneous development of liver tumors, thus the study results were not usual.

At the time, Steven Dentali, Ph.D., chief science officer for the American Herbal Products Association (AHPA) presented data showing the extract used in the NTP study was chemically different from commercially available ginkgo products and recognized pharmacopoeial standards.

The current Toxicologic Pathology study report looked at the data on B6C3F1 mice exposed to ginkgo extract and found a complex mechanism involving specific genes (H-ras and Ctnnb1), communication pathways within cells, and stress from both reactive oxygen species and foreign chemicals. Seemingly addressing Dr. Robert's earlier concern, the authors noted the study "illustrates the marked differences between these tumors and those arising spontaneously in the B6C3F1 mouse." They further contend the molecular changes observed in liver carcinogenesis in the ginkgo-treated mice might be relevant to human health.

Responding to the current study on mechanisms, AHPA repeated its concern that the ginkgo extract used in the study is not chemically similar to commercially available ginkgo used in products for human consumption. It further recommended the research should clarify the results are only applicable tot he extract used in the study itself.