Did you remember to take your ginkgo this morning? If you did, hoping it would prevent future memory problems, there’s now reason to think twice about that regimen. A recently published, six-year clinical study suggests Ginkgo biloba might not be particularly useful for preventing dementia in the elderly. In the double-blind study, 3,069 volunteers between the ages of 75 and 96 were given either 240 mg a day (120 mg twice daily) of the leading ginkgo extract or a placebo, and were evaluated for signs of dementia every six months at five different academic centers. By the end of the study, there was no statistical difference in the incidence of Alzheimer’s disease between the two groups.
The study has several potential weaknesses, however. The authors acknowledged it could take more than six years for symptoms of dementia to appear. In addition, only about 60 percent of the subjects were compliant in taking the ginkgo or the placebo by the end of the trial. Another potential weakness was the lack of an active control—a third arm of the study to compare ginkgo against a pharmaceutical drug. (This was not possible because there is no conventional drug to prevent the onset of dementia.)
Mark Blumenthal, founder and executive director of the American Botanical Council (ABC), reminds us that “a significant body of scientific and clinical evidence supports the safety and efficacy of ginkgo extract for both cognitive function and improved circulation.” In a press release, the ABC emphasizes that numerous clinical trials have shown ginkgo leaf extract to be effective for treating symptoms of existing dementia; the new study focused on long-term prevention of dementia. At least 11 previous clinical studies have shown ginkgo leaf extracts helpful for increasing short-term memory and concentration.
At least four other clinical studies are underway to show if ginkgo extracts can prevent or lessen the progression of dementia.
For more information, see The Journal of the American Medical Association Nov. 19, 2008; 300(19):2253-2262.