A large study examining the effects of the medicinal herb Ginkgo biloba concludes that it does not prevent Alzheimer’s disease or other forms of dementia. The findings, presented in the Journal of the American Medical Association, cast serious doubt on the future of ginkgo as a preventative measure for dementia, a disorder that affects more than 5 million people in the United States.

The eight year long Ginkgo Evaluation of Memory (GEM) Study involved over 3,000 patients age 75 and older, some of whom had a condition that can be an early harbinger of dementia called mild cognitive impairment. The results showed that among both healthy and mildly impaired participants, taking two 120 milligram doses of ginkgo a day had no effect on the development of dementia in general or Alzheimer’s disease specifically, which is the suspected cause of the vast majority of dementia cases.

Extract from the leaves of the Ginkgo biloba tree has powerful anti-inflammatory and antioxidant effects, which suggested that it might help protect the brain from the processes that lead to Alzheimer’s disease. Earlier lab tests also demonstrated that ginkgo can protect brain cells from the same problems that occur in Alzheimer’s disease. Despite this, the study appears to demonstrate conclusively that ginkgo is not helpful in preventing Alzheimer’s disease in older adults.

While the study did not find any positive effects of ginkgo, there did not appear to be any significant negative effects either. Taking the supplement did not affect the rate of coronary artery disease, stroke, or mortality. The study did not examine this possibility that ginkgo could have an effect on the development of dementia if people started taking it earlier, such as in middle age. There may also still be role for ginkgo in treating, rather than preventing, dementia.

Earlier research on ginkgo and memory has provided mixed results. Still, annual sales of the supplement in the U.S. reached an estimated $107 million in 2007.

If you take Ginkgo biloba, it is a good idea to do so under the supervision of a medical professional. People on the blood thinner warfarin shouldn't take ginkgo because of the risk of increased bleeding. Previous studies have also suggests an association between ginkgo and increased risk of “mini strokes” known as TIAs.

For more information, see the Healia Health Guide on Alzheimer’s Disease or visit the Healia Health Communities for Alzheimer’s Disease and Dementia.  You can also get answers to your questions about ginkgo at the Healia Health Communities for Dietary Supplements or the Healia Health Community for Complementary and Alternative Medicine.

 ^{Photo (adapted): colros, Flickr, Creative Commons}