Effects of American ginseng (Panax quinquefolius) extract on human neurocognitive function: a review.

Compared with Panax ginseng (Asian ginseng), Panax quinquefolius (American ginseng) has received relatively little research attention. Nevertheless, across several clinical trials a common finding is that P. quinquefolius extracts improve aspects of mood, mental fatigue, and cognitive function. This review details the findings from double-blind, randomized, controlled clinical trials which included assessment of cognitive performance, fatigue, or mood, individually or in combination. Limited fatigue benefits were observed in cancer patients at high doses (2000mg). The most notable effects at lower doses (100mg-400 mg) included enhancement of attentional and working memory performance in healthy adults and in Schizophrenia patients. Several studies also highlighted potential mechanisms underlying the cognitive effects of P. quinquefolius. These include increased activation of frontoparietal neural circuits and, in the context of the gut-brain axis, alterations of the human gut microbiome composition. The effects are also consistent with cholinergic modulation. Such effects suggest that P. quinquefolius extract may have benefits to everyday cognitive function.