Forgot your 10 o'clock appointment? Can't remember where you placed that report you worked on all night? Can't find your car keys? Again? It doesn't matter if you're sixteen or sixty - we all fall victim to a memory lapse now and then. And a little boost to our mental acuity would sure come in handy from time to time. Perhaps if we had more command of our memory, we would find more humor and less recognition in the bumper sticker that says, If I could remember your name, I'd ask you where I left my keys.
One of the most widely used herbal products to enhance memory and cognitive function is an extract of the leaves of Ginkgo biloba, which is believed to be the oldest tree species on earth. In fact, so popular is this remedy for declining memory that in Germany alone, over 6 million prescriptions were written for ginkgo in a single year. (That's right: prescriptions. In Germany and many other countries, ginkgo is considered a drug.)
GINKGO MAKES YOUNG ADULTS SHARPER
Although ginkgo has traditionally been associated with improving memory decline in the elderly, there is evidence that it can improve mental function in young people as well. One recent study published in Psychopharmacology, a medical journal that focuses on how drugs and herbal compounds affect the brain, reports that even 20-year-olds can improve their cognitive performance after taking a single daily serving of ginkgo.1
A separate study shows that extended use of ginkgo also benefits younger adults who normally exhibit no obvious memory dysfunction.2 Specifically, the speed at which they process information increases after taking ginkgo supplements for one month. Together, these studies demonstrate that ginkgo not only benefits a geriatric population but may also enhance cognitive and information-processing regions of the brain in healthy young adults.
GINKGO WORKS IN TWO WAYS
It has long been known that ginkgo improves blood circulation and promotes the cellular uptake and utilization of nutrients carried in the blood. In addition, ginkgo appears to increase the amount of blood flow directly to the brain.3 Not surprisingly, researchers initially believed that improved circulation in the brain, which increases the amounts of oxygen and glucose delivered to the neurons (brain cells), was responsible for improved cognitive performance. While this is still likely to be true, additional factors may figure in the ginkgo/cognition equation. Researchers now believe that ginkgo may act directly on the neurons. They propose that ginkgo may stimulate neuronal activity and help protect the cells from injury, thereby preserving their function. Thus a dual action may be at work in ginkgo's effects on our brains.
HOW COGNITIVE FACTORS ARE ASSESSED
Researchers who work on neural cognition to try to understand how our brains process information use a standardized (and therefore reproducible) group of tests to generate data. Collectively called the "Cognitive Drug Research (CDR) computerized assessment battery," the tests are administered using images on computer screens. They evaluate, among other things, short-term memory - for example, by measuring how accurately subjects remember a series of words, pictures, or numbers immediately after seeing them, and again after about 15 minutes; reaction time - how quickly subjects respond to a visual cue; and spatial memory - remembering where a particular visual cue appears in a lattice (much like the old TV show Concentration, where contestants had to remember where each of a pair of matching images was located in a large grid in order to win fabulous prizes).
Figure 1. Schematic diagram of the Cognitive Drug Research computerized assessment battery. The nine tests listed in the left column generate the quantitative measures listed in the middle column. These measures determine the assessment of the four cognitive factors shown in the right column. The arrows show which measures contribute to which cognitive factors. See the text for further explanation. (From Reference 1.)
A SINGLE DOSE IS EFFECTIVE WITHIN HOURS
A group of researchers in England used the CDR battery described above to determine the effects of a single dose of ginkgo on cognitive performance in a group of 20 young adults, aged 19-24 (average age 20).1 They were randomized to receive 120 mg, 240 mg, or 360 mg of a standardized ginkgo extract (which contains 24% ginkgo flavone glycosides and 6% terpene lactones) or a placebo. Each individual's ability to perform the tests in the CDR battery was measured at 1, 2.5, 4, and 6 hours after the ginkgo was administered.
The most dramatic response in this study was observed in the speed-of-attention category (which records the reaction times from three separate tasks that measure attention) following administration of the highest dose of ginkgo (360 mg). While there was no difference between this treatment group and the control group 1 hour after administration, there was a dramatic improvement in reaction times at the 2.5-hour time point, and it persisted throughout the follow-up period to the final test at 6 hours. The 240-mg dose gave good results in this category too, with significant improvement in reaction times occurring during the period from 2.5 hours to 6 hours.
The other three cognitive factors - accuracy of attention, quality of memory, and speed of memory - showed more erratic responses, with benefits appearing at different times and with different doses. For example, the quality of memory improved significantly when measured 1 hour and 4 hours after administration of 120 mg of ginkgo. This trend was mirrored with the 240-mg dose, but the effects were less dramatic. The speed of memory (assessed by means of four separate computerized memory tasks) was significantly improved 2.5 hours after administration of the 360-mg dose of ginkgo. A less dramatic improvement was recorded at the 6-hour time point (this was also true of the 120-mg dose). Interestingly, the 240-mg dose appeared to depress the speed of memory at the 4-hour time point.
What does all this mean? Well, ginkgo produces a sustained and measurable improvement in speed of attention in healthy young adults from 2.5 hours to 6 hours following a single dose (240 mg or 360 mg) - that much is clear. But what about the other categories? While there do appear to be benefits in the other cognitive factors measured, they are both dose- and time-dependent in erratic ways. The authors of this study note that additional research is needed to clarify these anomalies, and they suggest the possibility that a daily regimen of ginkgo may provide more consistent results. Read on . . .
SUSTAINED USE = SUSTAINED BENEFITS
It is exciting to realize that a single daily dose of ginkgo improves the attention and reaction time of healthy young adults. This observation naturally makes one wonder whether prolonged ginkgo supplementation would have additional and sustainable benefits. Is ginkgo just a flash in the pan that is good only for occasional use, or can it be used as a daily aid to improve cognitive powers? That is the question that a group of researchers in Australia decided to address.
Fifty healthy young volunteers between the ages of 18 and 40 (average age 30) took 360 mg of a standardized ginkgo extract every day for 30 days.2 At the beginning and the end of this period, they were given a battery of validated neuropsychological tests to determine the effects of ginkgo on cognitive performance. The tests used in this study were slightly different than the ones used in the trial discussed above, but the premise was the same. This battery included tests that measured attention and memory, but it also included a series of tests that monitored information processing, problem solving, and decision making.
The combined results of the test battery revealed statistically significant ginkgo-related improvements in memory processes and memory consolidation (the ability to remember specifics over a delayed time frame). Moreover, individual participants expressed subjective improvement in cognitive clarity as well as in memory and attention, following chronic administration of ginkgo through the study period. Thus, while the improvements were statistically significant based on scientific criteria, they were also obvious to the participants in the course of their daily lives. These reports are consistent with numerous anecdotal and historical reports that ginkgo extract improves cognitive function.
POWERING UP COGNITION AND MEMORY
So ginkgo extract may provide you with that added edge you need for finding those darned car keys. Every time. Whether you're sixteen or sixty.