Guayusa extract shows dose-dependent nootropic effects in study

A proprietary guayusa extract showed both cognitive/mood as well as psychomotor benefits in a dose-dependent manner in a recent study funded by the brand holder. 

The new research was published in the Journal of the International Society of Sports Nutrition. It was the work of a research team from the University of Iowa Department of Health and Human Physiology. 

The research was funded by Applied Food Sciences (AFS) of Kerrville, Texas. The study was done with the company’s proprietary guayusa extract, which is branded as AmaTea. The authors said they had full responsibility for the content and conclusions of the study. 

Long history of use 

Guayusa (Ilex guayusa) is an evergreen, broadleaf tree in the holly family. It is native to the western portions of the Amazonian rainforest. The plant, which has a long history of traditional use in the form of teas brewed with the leaves, has been cultivated for centuries. AFS says it works with a network of farmers in the region to source its organic raw material. 

The leaves contain caffeine, and extracts of the leaves are often used in products to offer a natural caffeine source. However, the leaves also contain chlorogenic acids.  

The study’s authors noted that past research opens the door for an entourage effect between the two substances, especially when a nootropic effect (as opposed to a mere stimulant effect) is desired. In this context, a nootropic could be defined as a product that boosts cognitive function, cognitive flexibility, concentration and attention. 

Two aspects of extract working together 

Caffeine works primarily by acting as an adenosine receptor antagonist, which indirectly alters the release of neurotransmitters that include dopamine, serotonin, and norepinephrine. This works to heighten arousal, making caffeine users feel more focused and energetic. 

The authors noted that caffeine shows a mood-heightening quality at low to moderate doses, while at higher doses it can increase feelings of anxiety and jitteriness. Meanwhile, recent research has shown that chlorogenic acid may boost mood all on its own. 

Because of the dose-dependent nature of caffeine’s effects, the researchers designed a study to delineate the effects of the branded extracts at both a low (600 milligrams) (mg) and high (1200 mg) dose. 

The researchers used a blinded, placebo-controlled crossover design with a cohort of 25 younger, healthy and physically active subjects. All the subjects consumed a low and high dose of the guayusa extract and an equivalent placebo. 

For each of the three experimental rounds, the subjects arrived at the testing facility where, after a period of rest, their baseline blood pressure and pulse were recorded. Then, they took one of the three interventions followed by rest. 

Immediately thereafter, they performed a battery of cognitive tests and filled out mood questionnaires. They also performed four validated hop tests to examine the psychomotor effects of the two extracts. 

Dose depends on desired effects 

The results showed some surprising effects that were in fact dose dependent. The low-dose guayusa leaf extract (GLE) improved mood and cognitive performance, while the high-dose GLE was more effective at improving psychomotor speed in the hop test. Both extracts increased blood pressure, but not heart rate. The high dose did tend to increase jitteriness, but only among the female subjects, the researchers said. 

“Our findings have important implications for GLE dosing, which should be dependent on the goal of supplementation and the target population,” they concluded.