Asian Ginseng Extract G115® Improves Aspects of Working Memory and Self-Reported Calmness
Reviewed: Reay J, Scholey A, Kennedy DO. Panax ginseng (G115) improves aspects of working memory performance and subjective ratings of calmness in healthy young adults. Hum Psychopharmacol Clin Exp. 2010;25:462-471.
Numerous studies in humans have demonstrated that a single dose of a proprietary Asian ginseng (Panax ginseng, Araliaceae) extract, standardized to 4% total ginsenosides (specifically G115, aka Ginsana®; Pharmaton SA; Lugano, Switzerland) improves certain aspects of cognitive performance in healthy young subjects. In contrast, only 3 human clinical studies have evaluated the ability of multiple daily doses of Asian ginseng use to affect cognitive processes in this population. These studies have shown an improvement in working memory, speed of performing mental arithmetic, and faster reaction times. Only one of the 3 studies evaluated G115. Hence, the purpose of this randomized, placebo-controlled, double-blind, crossover study of 8 days daily dosing was to investigate G115’s affect on working memory processes in more detail.
Thirty healthy men and women (mean age 23 years) participated in this study conducted at Northumbria University, Newcastle Upon Tyne, UK. All subjects were alcohol- and caffeine-free for 12 hours prior to baseline and abstained from these substances on testing days. Each morning, subjects ingested placebo, 200 mg G115, or 400 mg G115 for 8 days. There was a washout period of 6 days before the subjects were crossed over to another treatment. Subjects were tested on the first day and eighth day of each treatment period. Assessments were conducted 1, 2.5, and 4 hours post-dose. The battery of 4 cognitive assessments included: subjective mood (Bond-Lader visual analogue scales) and working memory (computerized Corsi block tapping task, N-back task, and random number generation task). Subjects were required to eat the same breakfast and lunch for the duration of the study period.
There was no significant multiple dose treatment-related effect over and above the acute effect for any outcome measure (i.e., for the sub-chronic, 8-day duration). In contrast, there were acute effects associated with treatment. The 200 mg treatment significantly improved self-reported ratings of calmness on day 1 at 2.5 hours (P = 0.012) and 4 hours (P < 0.0001) post-dose and on day 8 at 1 hour (P = 0.029) and 4 hours (P = 0.015) post-dose. The 400 mg treatment significantly improved self-reported ratings of calmness only on day 1 at 2.5 hours (P = 0.007) and 4 hours (P < 0.0001) post-dose. The Three Back Reaction Time Task revealed that, compared with placebo, the 400 mg dose resulted in significantly faster response times at 2.5 hours on day 1 (P = 0.023) and day 8 (P = 0.001). In contrast, the 200 mg dose led to significantly slower response times compared with placebo on day 1 at 1 hour (P = 0.0004), 2.5 hours (P = 0.046), and 4 hours (P = 0.003) post-dose, and on day 8 at 1 hour (P = 0.004) and 2.5 hours (P = 0.0001) post-dose. Similarly, on the Three Back Task Sensitivity Index, compared with placebo, the 400 mg dose resulted in a significantly improved sensitivity index on day 1 and day 8 at 1 hour (P < 0.0001), 2.5 hours (P < 0.0001), and 4 hours (P < 0.0001) post-dose. In contrast, the 200 mg dose led to significant impairment reflected in the sensitivity index, compared with placebo, on day 8 at 4 hours (P = 0.02) post-dose.
No other measures were significantly modulated by treatment. Safety was not assessed (presumably because numerous previous clinical trials on G115 have exhibited a high safety profile, as has common traditional use of various generic ginseng preparations over many centuries).
The authors conclude that G115 Asian ginseng extract had no effect following an 8-day dosing regimen. This is the first study to demonstrate a mood associated effect. The authors believe this effect may be due to the purported anxiolytic properties of ginseng. However, there have been no clinical studies assessing its anxiolytic properties in humans.
This study supports other reports that an acute dose of Asian G115 extract can affect cognitive function in young healthy subjects. However, this was the first study of G115 to include a comprehensive global assessment of working memory. The authors conclude that the 400 mg dose can modulate working memory performance. They note also that similar to their findings, other researchers have reported a decline in cognitive performance with the acute 200 mg dose (the average recommended daily dose). The authors do not have an explanation for this effect, particularly since the mechanism underlying the cognitive effects are unknown.
A limitation of the study is that 8-day dosing may not be long enough to see a chronic effect. Although the authors conclude that G115 can modulate working memory performance, as emphasized by the title, it is more accurate to say that G115 improves aspects of working memory.
—Heather S. Oliff, PhD