New evidence showing that supplements of the ginkgo biloba herb can improve memory was presented this week at the annual meeting of the Society for Neuroscience.
Researchers at the UCLA Neuropsychiatric Institute reported that they found significant improvement in verbal recall among a group of people with age-associated memory impairment who took the herbal supplement for six months when compared with a group that received a placebo.
The UCLA study, which used positron-emission tomography (PET), 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 added 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. But previous controlled clinical trials on ginkgo biloba's effects on verbal recall have yielded conflicting results.
A study published in JAMA last year found ginkgo biloba to have no beneficial effect on memory and related mental functions of healthy older adults. The study was carried out on 230 volunteers over the age of 60 who were physically and mentally healthy. Critics suggested that much longer duration study would be required to assess improvements in healthy adults, compared to in those with mild memory or cognitive problems.
There have also been concerns about variation among products on the market. "The research also raises questions regarding the significance of supplement quality and treatment duration," said principal investigator of the new study, Dr Gary Small, a UCLA professor on aging and director of the Aging and Memory Research Center at the UCLA Neuropsychiatric Institute. He added that the quality of retail supplies varies widely. "We used only the highest grade of ginkgo biloba in conducting our research."
A ConsumerLab review earlier this year found that the quality of the active ingredient in ginkgo supplements seemed to have dropped significantly in the last three years.
However 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.
The findings were reported earlier this week during the Society for Neuroscience meeting, held in New Orleans, LA.