The UCLA study, released at the annual meeting of the Society for Neuroscience, held Nov. 8-12, in New Orleans, LA, used positron-emission tomography (PET) and found that for subjects taking gingko biloba, improved recall correlated with better brain function in key brain memory centers.
However, actual changes in brain metabolism, measured by PET for the first time, did not differ significantly between the study's two volunteer groups. Researchers noted that although all volunteers taking gingko biloba experienced better verbal recall, a larger sample size might be needed to effectively track brain metabolism results.
"Our findings suggest intriguing avenues for future study, including using PET with a larger sample to better measure and understand the impact of gingko biloba on brain metabolism," said Dr. Linda Ercoli, lead author of the study and an assistant clinical professor at the UCLA Neuropsychiatric Institute.
Gingko biloba is a Chinese herb often used as a dietary supplement to treat memory loss. The UCLA study and previous controlled clinical trials on ginkgo biloba's effects on verbal recall have yielded conflicting results.
"The research also raises questions regarding the significance of supplement quality and treatment duration," said principal investigator Dr. Gary Small, a UCLA professor on aging and director of the Aging and Memory Research Center at the UCLA Neuropsychiatric Institute. "The Food and Drug Administration does not regulate dietary supplements, and the quality of retail supplies varies widely. We used only the highest grade of ginkgo biloba in conducting our research."
Small also noted that the six-month UCLA study is one of the first to measure the effects of gingko biloba over a longer period of time. Most previous studies have measured the effect of the supplement over 12 weeks or less.
The study examined the impact of ginkgo biloba, compared to a placebo, in 10 patients, aged 45 to 75, who did not have dementia but complained of mild age-related memory loss. Four subjects received 120 mg of ginkgo biloba twice daily, and six received a placebo or inactive substance such as a sugar pill.
Researchers used cognitive tests to measure verbal recall and PET to measure brain metabolism before and after the treatment regimen. Magnetic resonance imaging was used to determine regions of interest to be examined by PET.
Funding for the study was provided by Dr. Willmar Schwabe GmbH & Co., the John Douglas French Alzheimer's Foundation, the Louis and Harold Price Foundation, the Larry L. Hillblom Foundation and the UCLA Center on Aging.
The UCLA Neuropsychiatric Institute is an interdisciplinary research and education institute devoted to the understanding of complex human behavior, including the genetic, biological, behavioral and sociocultural underpinnings of normal behavior, and the causes and consequences of neurophychiatric disorders. More information is available online at www.npi.ucla.edu.