June 6, 2013 -- In a June 3, 2013 letter, the Center for Science in the Public Interest (CSPI) urged the Food and Drug Administration (FDA) to prohibit sale of foods and dietary supplements that contain ginkgo (Ginkgo biloba) leaf.
CSPI's request would apply to products that contain any amount of any extract of ginkgo leaf. Its letter cites a recent study (TR 578) by the National Toxicology Program (NTP) in which lab rodents were administered, via corn oil gavage, a specific ginkgo extract at doses up 2,000 mg/kg bodyweight every day for nearly the entire lifespan of the test animals. The NTP study concludes that there is "clear evidence of carcinogenic activity" in mice that had been given this ginkgo extract. In its letter to FDA, CSPI characterized this finding as establishing that "this herbal ingredient ... causes cancer in animals and presumably in people."
"CSPI's representation of the conclusions of the NTP study, conducted on one brand of ginkgo extract, is completely inaccurate," said Michael McGuffin, AHPA president. "In 'presuming' any relevance of this research to humans, CSPI either misunderstands or completely ignores the limited applicability of this and all such NTP rodent studies."
NTP was founded in 1978 as an interagency program to coordinate toxicology research and testing across the U.S. Department of Health and Human Services. All of its technical reports, including its recent report on one specific ginkgo extract, clearly state that study results do not establish evidence of harm to humans. For example:
- "Extrapolation of these results to other species, including characterization of hazards and risks to humans, requires analyses beyond the intent of these reports."
- "... the actual determination of risk to humans from chemicals found to be carcinogenic in laboratory animals requires a wider analysis that extends beyond the purview of these studies."
This limitation is also noted in TR 578 by FDA's representative to NTP, Dr. Paul Howard, who observes that NTP reports "...are not meant to evaluate risk for humans."
In addition and as AHPA has previously noted, the specific ginkgo extract used by NTP is dissimilar to the most prominently marketed ginkgo extract. The Chinese supplier of this extract, Shanghai Xing Ling, holds four U.S. patents for a proprietary ginkgo leaf extract, a fact that was not disclosed in the NTP study. This supplier's patents include declarations that indicate its differences from other ginkgo extracts, stating, for example, "Until now it has not been possible to prepare such highly concentrated extracts from Ginkgo biloba leaves."
"A thorough reading of the NTP ginkgo study indicates that the results are associated with force-feeding excessively high quantities of Shanghai Xing Ling brand ginkgo extract to mice over their entire lifetimes," added McGuffin. "But extrapolation of this risk to other ginkgo extracts or to humans is scientifically invalid."
CSPI's letter to FDA has been the subject of widespread reporting in the press. Of particular interest is an article published on June 3 in the New York Daily News, in which an FDA spokeswoman stated, "...it is not scientifically valid to conclude with certainty that dietary supplement products containing gingko biloba are unsafe based solely on data from the new NTP study ... [and] there may be differences in the extract used in these studies in contrast to what is available on the market for gingko biloba dietary supplements."
The Daily News article also quotes CSPI's executive director, Michael Jacobson, as follows: "The dietary supplement industry is full of snake oil salesmen."
"It appears that Dr. Jacobson's view of the supplement trade has disrupted his ability to separate the facts from his organization's speculations," observed McGuffin.