AMSTERDAM – American ginseng significantly improved working-memory performance in a double-blind, placebo-controlled crossover study of healthy young adults presented at the annual congress of the European College of Neuropsychopharmacology.
“This preliminary study has identified robust working-memory enhancement following the administration of American ginseng. These effects are distinct from those of Asian ginseng, and suggest that psychopharmacological properties depend critically on ginsenoside profiles,” said Andrew Scholey, Ph.D., professor of behavioral and brain sciences at the Brain Sciences Institute at Swinburne University, Melbourne, Australia.
Dr. Scholey, who led the study, said that previous studies have shown that Asian ginseng (Panax ginseng) lowers blood glucose, improves cognitive performance, and alleviates the mental fatigue that is associated with intense cognitive processing.
“American ginseng (Panax quinquefolius) shares Panax’s glycemic properties, but no previous studies have been conducted to evaluate the capacity of American ginseng to modulate cognitive function,” Dr. Scholey said. “The availability of a highly standardized extract of P. quinquefolius (Cereboost) led us to evaluate its neurocognitive properties in humans for the first time.”
The randomized, double-blind, placebo-controlled, crossover trial study involved 32 healthy young adults. Subjects were assessed for acute mood, neurocognitive, and glycemic effects of three doses (100, 200, and 400 mg) of American ginseng (standardized to 10.65% ginsenosides). On study days, separated by at least a 7-day washout period, participants’ mood, cognitive function, and blood glucose were measured at 1, 3, and 6 hours after administration of the ginseng.
To measure cognitive effects, investigators used the COMPASS (Computerized Mental Performance Assessment System) battery, which was developed to include tests that have proved sensitive to nutritional manipulations. COMPASS gauges performance on tasks of attention, working memory, secondary memory, and executive function.
The specific cognitive tests included word presentations, immediate word recall, picture presentations, face presentations, simple reaction times, choice reaction times, four-choice reaction times, Stroop color-word task, numeric working memory, alphabetic working memory, Corsi block-tapping task, N-back task, delayed word recall, delayed word recognition, delayed picture recognition, delayed face recognition, serial sevens subtraction task, serial threes subtraction task, and rapid visual information processing or Bakan task.
The study found, for the first time, cognitive and mood enhancements after the administration of American ginseng. Cognition-enhancing effects of the extract were observed across a range of cognitive parameters at a range of doses, reported Dr. Scholey, whose study was published recently (Psychopharamacology 2010 July 31 [doi:10.1007/s00213-010-1964-y]).
“The most striking finding was a significant improvement of working-memory performance,” Dr. Scholey reported. Compared with placebo, all doses of the extract were found to improve some aspect of cognition.
For all doses combined, a significant effect of treatment was observed for choice reaction time accuracy (P = .030), for numeric working memory speed (P = .007), for speed of alphabetic working memory (P = .04), and for Corsi block score (P = .041). These data represent enhancement effects predominantly on working-memory processes, and to some degree on short-term verbal declarative memory and attention, he said.
No significant baseline differences were found between conditions, showing that posttreatment effects were not attributable to differences in baseline performance, he added.
No differences were observed on blood glucose levels, which rules out any interpretation of the cognitive facilitation effects as being attributable to effects of glucose on insulin-mediated mechanisms. The lack of glycemic effects suggests that these effects can occur independently of changes in blood glucose, at least in healthy younger populations, Dr. Scholey said.
In the published report, the investigators noted that the findings should be treated with a degree of caution.
“Firstly, this is the first investigation into the neurocognitive effects of American ginseng. Clearly, the study needs at least partial replication, possibly with more focus on specific working-memory processes. Secondly, given the exploratory nature of the study, no adjustment was made for multiple comparisons,” he said. Further research is needed in other populations, such as in older individuals and those with cognitive problems.
Disclosures: The study was sponsored by Naturex, maker of Cereboost.