WASHINGTON D.C. (WUSA9) -- The National Institutes of Health's National Toxicology Program just released a study that finds Ginkgo biloba, a herbal remedy and dietary supplement, causes cancers of the thyroid gland in male and female rats.
It's used in energy drinks such as Rockstar, Crunk, Hansen's Energy Pro, Guru, and Steven Seagal's Lightning Bolt.
The leaves of the Ginkgo biloba tree have long been advertised as a remedy that can improve memory and brain function.
Scientists at NIH tested groups of 50 male and female rats, giving a dosage of Ginkgo biloba extract in corn oil, five times a week for two years.
While the groups were exposed to different amounts of the extract, every rat given any dosage had some variety of lesions.
The Center for Science in the Public Interest has downgraded Ginkgo from "safe" to "avoid" in its Chemical Cuisine guide to food additives.
"Ginkgo has been used in recent years to let companies pretend that supplements or energy drinks or supplements with it confer some sort of benefit for memory or concentration," said CSPI executive director Michael F. Jacobson. "The evidence for those claims has been dubious, at best. The pretend benefits are now outweighed by the real risk of harm."
The American Herbal Products Association (AHPA) disputes the relevance of the NTP report. They say the extract used in the study is not chemically similar to products sold for commercial use.
Dr. Steven Dentali, Ph.D., AHPA's Chief Science Officer says, "I'm disappointed that NTP did not adopt AHPA's recommendations to properly qualify the extract that was studied and its relevance to consumers and the marketplace."
AHPA also notes that text in the report says that it is not meant to evaluate risk for humans.
The extract is often sold as a supplement by various companies, including, GNC, NatureMade and Nature's Bounty.