The Examine.com editors have finished a page on Polygala tenuifolia, or as it’s known in traditional Chinese medicine, Yuan Zhi. Polygala tenuifolia is one of the 50 fundamental herbs in traditional Chinese medicine, and it’s often included in decoctions intended to improve cognitive health and well-being.
Unfortunately, only one human study has been conducted on Polygala tenuifolia. Researchers observed that healthy people supplementing Polygala tenuifolia experienced benefits to spatial organization, making it easier to organize and order diagrams and pictures. Memory retention and formation was not affected.
Animal research, however, suggests Polygala tenuifolia may have a restorative effect on cognition. Studies investigating animal models of cognitive decline and aging found that Polygala tenuifolia has a powerful effect when given to aging rodents. Healthy rodents, however, experienced no major benefits to cognition.
The aging rodents may have experienced cognitive benefits because Polygala tenuifolia supplementation increases brain growth factors, like brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF). It also has an antioxidant effect in the brain. Much more research is needed to investigate these mechanisms and how they may apply to supplementation.
Polygala tenuifolia may also have an antidepressant effect similar to ketamine, a rarely-prescribed antidepressant, since it has hallucinogenic and habit forming properties. After oral supplementation, both Polygala tenuifolia and ketamine cause a fast-acting and potent antidepressant effect. These compounds have a similar effect because both interact with the N-methyl-D-aspartate (NMDA) receptor.
Polygala tenuifolia is a promising brain enhancing herb, but much more research is needed before it can be recommended as a supplement. Preliminary evidence suggests it provides the most benefit when supplemented by people suffering from cognitive decline, while healthy people experience little to no benefit.