March 21, 2008
A small study in which elderly men and woman received the popular herbal "memory booster" ginkgo biloba suggested that the herb may be beneficial in reducing the risk of dementia. But because of its limited size, no one can be sure if the benefits were due to chance. The herb is taken by millions of older Americans to help ward off senior moments and, hopefully, the onset of Alzheimer's disease.
The three-year study, which appeared in the medical journal Neurology, followed 118 seniors aged 85 and older who did not have memory problems at the start of the study. Half of the study participants took ginkgo biloba extract three times a day. The others took a look-alike placebo.
During the study, 21 people developed mild memory problems that may have been signs of early Alzheimer's or other forms of dementia. Among those who developed memory problems, 14 were taking the dummy herb, while 7 were taking ginkgo. While those results suggest that ginkgo may have provided some protective benefits for memory, the numbers were not statistically significant.
The researchers, from Oregon Health & Sciences University, made an interesting observation when they reviewed the data at the end of the trial. Taking into account whether people followed directions in taking the study pills, they found that people who reliably took the supplement had a 68 percent lower risk of developing mild memory problems than those who took the placebo. This is a very interesting observation that makes it somewhat more plausible that ginko was having a protective effect.
"Further studies are needed to determine whether gingko biloba has any benefits in preventing cognitive decline and whether it is safe," said study author Hiroko Dodge, Ph.D., of the Department of Public Health and Center for Healthy Aging Research at Oregon State University in Corvallis. "The findings are interesting because ginkgo biloba is already widely used, readily available, and relatively inexpensive. One of the most pressing public health problems facing our society is the rapidly growing number of people who, due to their age alone, are at high risk of developing dementia. The potential to delay or prevent this is of great importance."
Herbal extracts of ginkgo biloba have been used for thousands of years in China for medical reasons, including improving circulation and keeping the memory sharp. Extracted from the double-lobed leaves of the ancient ginkgo tree that grows in city parks around the world, it is known to have blood-thinning properties that may have some benefits for circulatory and cardiovascular health. It also acts as an antioxidant.
Unfortunately, as with most non-prescription herbal remedies, it is hard to know how much of the active ingredient is really being supplied. That's because herbal remedies are not regulated like pharmaceutical drugs. Manufactures of "neutraceuticals" are not bound by law to insure that a high quality medication is actually being sold. The extract used in the study was a standardized extract, however.
Some earlier scientific reports suggest that the herb may have benefits for warding off ringing in the ears, poor circulation in the extremities, and other ills. Because it may boost blood flow to the brain, it may also have benefits for cognitive health as well. Some studies show that it may provide a mild and temporary memory boost to those who are already suffering form Alzheimer's.
On a cautionary note, the study also found that people taking ginkgo biloba were more likely to have a stroke or transient ischemic attack, sometimes called a mini-stroke, that may be a precursor to a full-blown stroke. Seven people taking ginkgo had strokes, while none of those taking placebo did. "Ginkgo has been reported to cause bleeding-related complications, but the strokes in this case were due to blood clots, not excessive bleeding, and were generally not severe," said Dr. Dodge.
Because of its blood-thinning properties, experts caution that anyone taking the herb should tell their doctors. It may interact with blood thinners or other medications, including aspirin and warfarin, to cause dangerous bleeding.
The study is the first randomized, controlled trial to look at the use of the herb ginkgo biloba in the oldest old. This age group is important to study, the researchers note, because over half of those with Alzheimer's and other forms of dementia in developed countries are in their 80s or older. The research was conducted at Oregon Health & Science University's NIA-Layton Aging & Alzheimer's Disease Center and the Oregon Center for Complementary and Alternative Medicine in Neurological Disorders. The study was supported by grants from the National Institute on Aging and the National Center for Complementary and Alternative Medicine. The ginkgo biloba extract was provided by Thorne Research, Inc.
To learn more about research into therapies to treat Alzheimer's and the search for a cure, visit www.ALZinfo.org, The Alzheimer's Information Site.
H. H. Dodge, Ph.D., T. Zitzelberger, M.P.H., R. S. Oken, M.D., et al: "A Randomized Placebo-Controlled Trial of Ginkgo Biloba for the Prevention of Cognitive Decline." Neurology, February 27, 2008.