Ginkgo Biloba
Ginkgo Biloba is a tree originally native to China. It has a long history of use in China for both food and medical purposes. The leaves are mostly used for the cognitive enhancing properties. Ginkgo biloba is one of the most popular herbal supplements for enhancing cognitive function. For this reason it has been studied extensively. So far much of the research is conflicting. There are high quality studies on the longer term use of ginkgo biloba extracts that show both positive and no effect. At the moment there does not appear to be any significant differences between the studies that could account for these inconsistencies. More studies are required to determine long term effects. What is more clear from the research is a very likely boost to cognition following short term supplementation. Positive effects have been demonstrated within hours of taking the supplement and continued use has shown benefits after a week. The longer the supplementation period the more likely that no effect would be demonstrated. For now this supplement is probably best used over very short periods (one week or less).
Most beneficial for - Effects seem not to be confined to a single group of people. May be slightly more effective in older people
Effective dose - 120mg up to 360mg of ginkgo extract per day has been reported to be effective
Length of action - Immediate up to 1 or 2 weeks of continual use (inconclusive over longer time periods)
Safety - No data available yet
Type cognition effected - Improvements to second memory, speed of information processing, working memory, executive processing, nonverbal memory, sustained attention and speed of attention have been reported
Enhancers - May be effective in combination with panax ginseng, phosphatidylserine or vinpocetine
Supporting Human Studies
Modulation of cognition and mood following administration of single doses ofGinkgo biloba, ginseng, and a ginkgo/ginseng combination to healthy young adults (Kennedy et al, 2002)
Healthy adults were given 360mg of a ginkgo extract or a placebo then cognitive tests performed 1, 2.5, 4 and 6 hours after the dose. The dose of ginkgo biloba was associated with improved second memory performance on a computerized test. Serial threes, serial sevens and subtraction tasks were also improved by the ginkgo biloba extract.
Cognitive Performance, SPECT, and Blood Viscosity in Elderly Non-demented People Using Ginkgo Biloba (Santos et al, 2003)
Forty eight men between 70-90 years of age received either a dried ginkgo biloba extract or a placebo for 8 months. At the end of the study the group receiving the ginkgo biloba extract showed reduced blood viscosity, improved cerebral perfusion in certain areas and improved cognitive functioning compared to the placebo group.
Neuropsychological changes after 30-day Ginkgo biloba administration in healthy participants (Stough et al, 2001)
In this double blind placebo controlled trial 61 healthy participants received a ginkgo biloba extract or a placebo daily for 30 days. Statistical analysis at the end of the 30 days indicated that those taking the ginkgo biloba extract had significant improvements in speed of information processing, working memory and executive processing.
Effects on cognition and mood in postmenopausal women of 1-week treatment with Ginkgo biloba (Hartley et al, 2003)
Thirty one women between 53-65 were randomly assigned to receive 120mg/day of a ginkgo extract or a placebo for 7 days. The group receiving the ginkgo showed significant improvements in tests for nonverbal memory, frontal lobe function and sustained attention. There were no differences on delayed paragraph and picture recall or planning tests between ginkgo and placebo groups.
The effects of acute doses of standardized Ginkgo biloba extract on memory and psychomotor performance in volunteers (Rigney et al, 1999)
Thirty one volunteers aged 30-59 randomly received varying doses of ginkgo biloba extract (120, 150, 240 or 300mg) or a placebo for 2 days. Cognitive testing was performed before receiving the ginkgo biloba extract and at regular intervals after. Results showed that those taking the ginkgo biloba extract demonstrated improved memory function and in particular working memory. Higher doses were associated with a greater effect and those between 50-59 years were more likely to see improvements.
Differential cognitive effects of Ginkgo biloba after acute and chronic treatment in healthy young volunteers (Elsabagh et al, 2005)
In this double blind placebo controlled trial young healthy participants received 120mg of ginkgo extract or a placebo. One group was tested once 4 hours after receiving the first dose and the other group after 6 weeks taking the supplement daily. In both trials participants were tested for attention, working memory, mental flexibility, planning and mood. The group receiving the acute dose of ginkgo showed significant improvements vs the placebo in attention and memory tasks. The tests after 6 weeks showed there to be no effect on any of the tests. This suggests that healthy adults build resistance to ginkgo preventing it from working over the longer term.
The dose-dependent cognitive effects of acute administration of Ginkgo biloba to healthy young volunteers (Kennedy et al, 2000)
This study involved giving 19-24 year olds varying doses of a ginkgo extract (120mg, 240mg or 360mg) or a placebo before undergoing a battery of computer based tests measuring speed of attention, accuracy of attention, speed of memory and memory quality. The battery of tests were performed prior to dosing and 1, 2.5, 4 and 6 hours after dosing. Several factors improved at various times and doses however the most significant change was a dose dependent improvement in speed of attention. This was evident at 2.5 hours and still present at 6 hours.
A double-blind, placebo controlled study of Ginkgo biloba extract (‘Tanakan’) in elderly outpatients with mild to moderate memory impairment (Rai et al, 1991)
Thirty one patients over the age of 50 showing mild to moderate memory problems were randomly assigned 120mg extract of ginkgo biloba extract daily or a placebo for 6 months. Cognitive assessments were done before administration of the ginkgo bilioba and at 12 and 24 weeks into the study. Ginkgo biloba was shown to improve cognition compared to the baseline tests. Tests for digit copying were significantly improved after 12 weeks and median speed of response testing was significantly improved after 24 weeks compared to the placebo group.
Supporting Animal Studies
The Effects of an Extract of Ginkgo biloba, EGb 761, on Cognitive Behavior and Longevity in the Rat (Winter, 1997)
Rats were treated with a ginkgo biloba extract before and after undergoing cognitive tasks. The administration of ginkgo biloba extract before a task improved their results while after the task did not help consolidate learning. Chronic administration of ginkgo biloba extract resulted in fewer repetitions to learn a new task and fewer errors. Rats chronically treated also lived significantly longer than rats not receiving the extract. The extract also reduced retroactive and proactive errors in a delayed non-matching to position task.
A comparative study in rodents of standardized extracts of Bacopa monniera and Ginkgo biloba: Anticholinesterase and cognitive enhancing activities (Das et al, 2002)
Rats were administered varying doses of a ginkgo biloba extract (15, 30, 60mg/kg) daily for 7 days. Passive avoidance, increased latency and no transfer response tests were performed after the 7 day trial and compared to a control group. The group receiving the ginkgo biloba extract showed improved performance on the cognitve tests compared to the control group. The extract also reduce acetylcholinesterase activity in rats that took it.
Contradictory Studies
Ginkgo biloba: no robust effect on cognitive abilities or mood in healthy young or older adults (Burns et al, 2005)
In this double blind placebo controlled trial 93 older adults and 103 younger adults received either 120mg of ginkgo biloba extract or a placebo daily for 12 weeks. Cognitive abilities, executive function, attention and mood were tested at the end of the trial. Within the older group only longer term memory tasks showed improvement vs the placebo group. In the younger group no differences were observed between the ginkgo and placebo group.
Safety and Efficacy of a Ginkgo Biloba–Containing Dietary Supplement on Cognitive Function, Quality of Life, and Platelet Function in Healthy, Cognitively Intact Older Adults (Carlson et al, 2007)
Ninety mentally healthy elderly participants received either a supplement containing 160mg of ginkgo biloba, 68mg gotu kola and 180mg DHA or a placebo daily for 4 months. Cognitive tests were performed directly before the trial and after 4 months. No significant effects on cognition or platelet function were observed between the supplemental or placebo group following 4 months. The supplement was however found to be safe.
Ginkgo for Memory Enhancement (Solomon et al, 2002)
In this double blind placebo controlled trial 230 elderly subjects without cognitive problems received 120mg daily of ginkgo biloba supplement similar to current over the counter supplements or a placebo for 6 weeks. No significant differences were observed between the two groups on any cognitive tests.
Ginkgo biloba for Preventing Cognitive Decline in Older Adults (Snitz et al, 2009)
In this double blind placebo controlled trial 3069 adults between the ages of 72 to 96 received 120mg of ginkgo extract twice daily or a placebo over an 8 year period. Over this period no differences were observed in rates of cognitive decline between ginkgo and placebo groups.
Effects of a combined extract of Ginkgo biloba and Bacopa monniera on cognitive function in healthy humans (Pradeep et al, 2004)
Eighty five healthy subjects received either Ginkgo biloba (120mg)/Bacopa Monniera (300mg) (Blackmores) supplement or a placebo for 4 week. Cognitive test were performed after 2 and 4 weeks on the regime. No significant improvements were observed between the two groups over this time frame.
Combinational Studies
Differential, dose dependent changes in cognitive performance following acute administration of a Ginkgo biloba/Panax ginseng combination to healthy young volunteers (Kennedy et al, 2001)
In this Placebo controlled double blind study 20 healthy adults received 320, 640 or 960mg of a combined ginkgo biloba/panax ginseng extract or the placebo on one day. Tests then took place 1, 2.5, 4 and 6 hours after the dose. The ginkgo/ginseng extract showed a dose dependent improvement in quality of memory measures. The highest dose producing the most improvement. This improvement was linked to second memory rather than working memory. The 320mg and 640mg doses showed a decrement in performance of a speed of attention test.
Acute cognitive effects of standardised Ginkgo biloba extract complexed with phosphatidylserine (Kennedy et al, 2007)
Twenty eight healthy adults received one of the following, 120mg ginkgo biloba extract, 120mg ginkgo/phosphatidylserine complex, 120mg ginkgo/phosphatidylcholine extract or a placebo. Follwoing a single dose cognitive tests were performed at 1, 2.5, 4 and 6 hours post treatment. Those receiving the ginkgo extract only saw insignificant improvements in cognitive tests. Those receiving the ginkgo/phosphatidylserine complex showed significant improvements in secondary memory and speed of memory tasks. All three treatments improved calmness.
The cognitive, subjective, and physical effects of a ginkgo biloba/panax ginseng combination in healthy volunteers with neurasthenic complaints (Wesnes et al, 1997)
In this double blind placebo controlled trial 64 healthy adults received either 80, 160 or 320mg of a ginkgo/ginseng extract or a placebo daily for 90 days. On day 90 one hour post dose tests showed a dose dependent improvements in a computerized cognitive test. This was reversed however 1 hour after the afternoon dose possibly suggesting that a longer inter-dosing interval would be preferable.
Cognitive effects of a ginkgo biloba/vinpocetine compound in normal adults: systematic assessment of perception, attention and memory (Polich et al, 2001)
In this double blind placebo controlled trial 24 healthy adults received a ginkgo biloba extract (40mg)/vinpocetine (10mg) or a placebo for 14 days. Results showed that the the ginkgo biloba/vinpocetine supplements increased the speed of short term working memory compared to the placebo.
Safety Studies
Most beneficial for - Effects seem not to be confined to a single group of people. May be slightly more effective in older people
Effective dose - 120mg up to 360mg of ginkgo extract per day has been reported to be effective
Length of action - Immediate up to 1 or 2 weeks of continual use (inconclusive over longer time periods)
Safety - No data available yet
Type cognition effected - Improvements to second memory, speed of information processing, working memory, executive processing, nonverbal memory, sustained attention and speed of attention have been reported
Enhancers - May be effective in combination with panax ginseng, phosphatidylserine or vinpocetine
Supporting Human Studies
Modulation of cognition and mood following administration of single doses ofGinkgo biloba, ginseng, and a ginkgo/ginseng combination to healthy young adults (Kennedy et al, 2002)
Healthy adults were given 360mg of a ginkgo extract or a placebo then cognitive tests performed 1, 2.5, 4 and 6 hours after the dose. The dose of ginkgo biloba was associated with improved second memory performance on a computerized test. Serial threes, serial sevens and subtraction tasks were also improved by the ginkgo biloba extract.
Cognitive Performance, SPECT, and Blood Viscosity in Elderly Non-demented People Using Ginkgo Biloba (Santos et al, 2003)
Forty eight men between 70-90 years of age received either a dried ginkgo biloba extract or a placebo for 8 months. At the end of the study the group receiving the ginkgo biloba extract showed reduced blood viscosity, improved cerebral perfusion in certain areas and improved cognitive functioning compared to the placebo group.
Neuropsychological changes after 30-day Ginkgo biloba administration in healthy participants (Stough et al, 2001)
In this double blind placebo controlled trial 61 healthy participants received a ginkgo biloba extract or a placebo daily for 30 days. Statistical analysis at the end of the 30 days indicated that those taking the ginkgo biloba extract had significant improvements in speed of information processing, working memory and executive processing.
Effects on cognition and mood in postmenopausal women of 1-week treatment with Ginkgo biloba (Hartley et al, 2003)
Thirty one women between 53-65 were randomly assigned to receive 120mg/day of a ginkgo extract or a placebo for 7 days. The group receiving the ginkgo showed significant improvements in tests for nonverbal memory, frontal lobe function and sustained attention. There were no differences on delayed paragraph and picture recall or planning tests between ginkgo and placebo groups.
The effects of acute doses of standardized Ginkgo biloba extract on memory and psychomotor performance in volunteers (Rigney et al, 1999)
Thirty one volunteers aged 30-59 randomly received varying doses of ginkgo biloba extract (120, 150, 240 or 300mg) or a placebo for 2 days. Cognitive testing was performed before receiving the ginkgo biloba extract and at regular intervals after. Results showed that those taking the ginkgo biloba extract demonstrated improved memory function and in particular working memory. Higher doses were associated with a greater effect and those between 50-59 years were more likely to see improvements.
Differential cognitive effects of Ginkgo biloba after acute and chronic treatment in healthy young volunteers (Elsabagh et al, 2005)
In this double blind placebo controlled trial young healthy participants received 120mg of ginkgo extract or a placebo. One group was tested once 4 hours after receiving the first dose and the other group after 6 weeks taking the supplement daily. In both trials participants were tested for attention, working memory, mental flexibility, planning and mood. The group receiving the acute dose of ginkgo showed significant improvements vs the placebo in attention and memory tasks. The tests after 6 weeks showed there to be no effect on any of the tests. This suggests that healthy adults build resistance to ginkgo preventing it from working over the longer term.
The dose-dependent cognitive effects of acute administration of Ginkgo biloba to healthy young volunteers (Kennedy et al, 2000)
This study involved giving 19-24 year olds varying doses of a ginkgo extract (120mg, 240mg or 360mg) or a placebo before undergoing a battery of computer based tests measuring speed of attention, accuracy of attention, speed of memory and memory quality. The battery of tests were performed prior to dosing and 1, 2.5, 4 and 6 hours after dosing. Several factors improved at various times and doses however the most significant change was a dose dependent improvement in speed of attention. This was evident at 2.5 hours and still present at 6 hours.
A double-blind, placebo controlled study of Ginkgo biloba extract (‘Tanakan’) in elderly outpatients with mild to moderate memory impairment (Rai et al, 1991)
Thirty one patients over the age of 50 showing mild to moderate memory problems were randomly assigned 120mg extract of ginkgo biloba extract daily or a placebo for 6 months. Cognitive assessments were done before administration of the ginkgo bilioba and at 12 and 24 weeks into the study. Ginkgo biloba was shown to improve cognition compared to the baseline tests. Tests for digit copying were significantly improved after 12 weeks and median speed of response testing was significantly improved after 24 weeks compared to the placebo group.
Supporting Animal Studies
The Effects of an Extract of Ginkgo biloba, EGb 761, on Cognitive Behavior and Longevity in the Rat (Winter, 1997)
Rats were treated with a ginkgo biloba extract before and after undergoing cognitive tasks. The administration of ginkgo biloba extract before a task improved their results while after the task did not help consolidate learning. Chronic administration of ginkgo biloba extract resulted in fewer repetitions to learn a new task and fewer errors. Rats chronically treated also lived significantly longer than rats not receiving the extract. The extract also reduced retroactive and proactive errors in a delayed non-matching to position task.
A comparative study in rodents of standardized extracts of Bacopa monniera and Ginkgo biloba: Anticholinesterase and cognitive enhancing activities (Das et al, 2002)
Rats were administered varying doses of a ginkgo biloba extract (15, 30, 60mg/kg) daily for 7 days. Passive avoidance, increased latency and no transfer response tests were performed after the 7 day trial and compared to a control group. The group receiving the ginkgo biloba extract showed improved performance on the cognitve tests compared to the control group. The extract also reduce acetylcholinesterase activity in rats that took it.
Contradictory Studies
Ginkgo biloba: no robust effect on cognitive abilities or mood in healthy young or older adults (Burns et al, 2005)
In this double blind placebo controlled trial 93 older adults and 103 younger adults received either 120mg of ginkgo biloba extract or a placebo daily for 12 weeks. Cognitive abilities, executive function, attention and mood were tested at the end of the trial. Within the older group only longer term memory tasks showed improvement vs the placebo group. In the younger group no differences were observed between the ginkgo and placebo group.
Safety and Efficacy of a Ginkgo Biloba–Containing Dietary Supplement on Cognitive Function, Quality of Life, and Platelet Function in Healthy, Cognitively Intact Older Adults (Carlson et al, 2007)
Ninety mentally healthy elderly participants received either a supplement containing 160mg of ginkgo biloba, 68mg gotu kola and 180mg DHA or a placebo daily for 4 months. Cognitive tests were performed directly before the trial and after 4 months. No significant effects on cognition or platelet function were observed between the supplemental or placebo group following 4 months. The supplement was however found to be safe.
Ginkgo for Memory Enhancement (Solomon et al, 2002)
In this double blind placebo controlled trial 230 elderly subjects without cognitive problems received 120mg daily of ginkgo biloba supplement similar to current over the counter supplements or a placebo for 6 weeks. No significant differences were observed between the two groups on any cognitive tests.
Ginkgo biloba for Preventing Cognitive Decline in Older Adults (Snitz et al, 2009)
In this double blind placebo controlled trial 3069 adults between the ages of 72 to 96 received 120mg of ginkgo extract twice daily or a placebo over an 8 year period. Over this period no differences were observed in rates of cognitive decline between ginkgo and placebo groups.
Effects of a combined extract of Ginkgo biloba and Bacopa monniera on cognitive function in healthy humans (Pradeep et al, 2004)
Eighty five healthy subjects received either Ginkgo biloba (120mg)/Bacopa Monniera (300mg) (Blackmores) supplement or a placebo for 4 week. Cognitive test were performed after 2 and 4 weeks on the regime. No significant improvements were observed between the two groups over this time frame.
Combinational Studies
Differential, dose dependent changes in cognitive performance following acute administration of a Ginkgo biloba/Panax ginseng combination to healthy young volunteers (Kennedy et al, 2001)
In this Placebo controlled double blind study 20 healthy adults received 320, 640 or 960mg of a combined ginkgo biloba/panax ginseng extract or the placebo on one day. Tests then took place 1, 2.5, 4 and 6 hours after the dose. The ginkgo/ginseng extract showed a dose dependent improvement in quality of memory measures. The highest dose producing the most improvement. This improvement was linked to second memory rather than working memory. The 320mg and 640mg doses showed a decrement in performance of a speed of attention test.
Acute cognitive effects of standardised Ginkgo biloba extract complexed with phosphatidylserine (Kennedy et al, 2007)
Twenty eight healthy adults received one of the following, 120mg ginkgo biloba extract, 120mg ginkgo/phosphatidylserine complex, 120mg ginkgo/phosphatidylcholine extract or a placebo. Follwoing a single dose cognitive tests were performed at 1, 2.5, 4 and 6 hours post treatment. Those receiving the ginkgo extract only saw insignificant improvements in cognitive tests. Those receiving the ginkgo/phosphatidylserine complex showed significant improvements in secondary memory and speed of memory tasks. All three treatments improved calmness.
The cognitive, subjective, and physical effects of a ginkgo biloba/panax ginseng combination in healthy volunteers with neurasthenic complaints (Wesnes et al, 1997)
In this double blind placebo controlled trial 64 healthy adults received either 80, 160 or 320mg of a ginkgo/ginseng extract or a placebo daily for 90 days. On day 90 one hour post dose tests showed a dose dependent improvements in a computerized cognitive test. This was reversed however 1 hour after the afternoon dose possibly suggesting that a longer inter-dosing interval would be preferable.
Cognitive effects of a ginkgo biloba/vinpocetine compound in normal adults: systematic assessment of perception, attention and memory (Polich et al, 2001)
In this double blind placebo controlled trial 24 healthy adults received a ginkgo biloba extract (40mg)/vinpocetine (10mg) or a placebo for 14 days. Results showed that the the ginkgo biloba/vinpocetine supplements increased the speed of short term working memory compared to the placebo.
Safety Studies