Ginkgo's brain benefits questioned
performance of healthy subjects, says a new study, but the high
level of cognitive function of the subjects to start with may
undermine the conclusions.
"These finding do not support the use of a ginkgo biloba-containing supplement for improving cognitive function or quality of life in cognitively intact, older, healthy adults.
However, high baseline scores may have contributed to the null findings," wrote lead author Joseph Carlson in the Journal of the American Dietetic Association .
Ginkgo is derived from the leaves of the ginkgo tree and has been used for thousands of years by the Chinese as a herbal remedy for a variety of ailments.
It contains potent antioxidants called flavoglycosides that have been shown to have neuroprotective effects in animal models of spinal cord injury.
Clinical trials in Germany and France reported that gingko biloba produced long-term improvements in cognitive function in older adults with dementia, but, according to Carlson and his co-workers from Stanford University report that there is only limited data looking at cognitive function and quality of life in healthy, non-demented older adults.
The researchers recruited 90 subjects (average age 72.6) and randomly assigned to receive either a placebo or a ginkgo biloba supplement (Nutrilite brand) containing 160 mg of ginkgo biloba, 68 mg of gotu kola, 180 mg of DHA, a bioflavonoid concentrate (100 mg) and vitamin A (300 IU) as beta carotene, for four months.
All participants were also given a standard once-daily multivitamin/multimineral supplement.
Cognitive function was measured using a battery of tests, including the Benton Visual Retention test, Controlled Oral Word Association, Judgment of Line Orientation, Modified Mini-Mental Status Examination, List Learning, and Symbol Digit Modalities.
Carlson reports that 78 subjects completed the trial (36 in the placebo group, 42 in the gingko group) and no significant changes were observed between placebo and gingko biloba groups, for any of the cognitive tests, nor for the 'quality of life' scores.
"These data do not support the use of a commercial ginkgo biloba-containing supplement to improve cognitive function or quality of life in healthy 65- to 85-year-old cognitively intact healthy adults with average to above-average cognitive function ," wrote the researchers.
However, "the high level of cognitive function in these study participants left little room for the potential enhancement of cognitive function," they added.
From a safety point of view, no adverse events were reported and the researchers concluded that the supplement was safe and did not alter platelet function.
"Given the widespread use of ginkgo biloba and selected research reporting benefits, further research is needed to determine the potential health effects of higher doses and longer-term use, particularly in older adults with normal or above-average cognitive function for their age," concluded the researchers.
Source: Journal of the American Dietetic Association March 2007, Volume 107, Issue 3, Pages 422-432 "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" Authors: J.J. Carlson, J.W. Farquhar, E. DiNucci, L. Ausserer, J. Zehnder, D. Miller, K. Berra, L. Hagerty and W.L. Haskell
