Should the use of Ginkgo biloba be restricted?

Researchers from Rheinischen Friedrich Wilhelms-UniVersitat, in Bonn, Germany think is should.

Here’s a summary of their rationale.

In addition to flavonoids and terpene lactones, G. biloba includes an allergenic and toxic compound called ginkgotoxin.

The seed of G. biloba, called gin-nan” in Japan, is known to be a medication and a food. But it is also the cause of “gin-nan” sitotoxism — food poisoning, which has been reported 70 times, with a 27% rate of death.

The symptoms of poisoning are convulsions, unconsciousness, and paralysis of the legs.

How does this happen?

Ginkgotoxin has a structural similarity to vitamin B6 and it interferes with metabolic steps related to the vitamin’s function or biosynthesis.

At special risk are children age 1 to 3 years who were affected in 58% of reported cases of intoxication.

And, a family with neonatal seizures has been described that carry a mutation in the gene called pyridoxol/pyridoxamine 5-phosphate oxidase (PNPO), which is involved in vitamin B6 metabolism. This suggests that ginkgotoxin may cause seizures by interfering with the functioning of PNPO or the supply of vitamin B6.

The bottom line?

The authors conclude, “In addition to the presumed, but not unequivocally proven, beneficial health effects of G. biloba products, these preparations also carry a clear potential for adverse effects, particularly in susceptible individuals. It is therefore important that the large number of G. biloba product users and their healthcare providers be made aware of these risks.”

The highest concentration of ginkgotoxin is found in the leaves during autumn. The risk could be minimized by not harvesting at this time. And of course, all of this can be prevented through quality control measures to remove ginkgotoxin during production of the ginkgo tablets.

1/31/10 12:08 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.