The study, published in the journal Nutrients, suggests that green tea and guarana may be useful strategies to improve academic performance and avoid the excess additives and sugar in carbonated and energy drinks that students may favor.
“These drinks, recognized worldwide as harmful to health, can be replaced with those studied in this work,” wrote researchers from Stefan cel Mare University of Suceava and Suceava County Emergency Clinical Hospital in Romania.
“Throughout the study, the consumption of guarana and green tea presented neurostimulating effects, based on the results obtained from the cognitive tests applied. However, it was found that guarana produces better results in terms of intellectual performance, compared to green tea.”
Nootropic effects of guarana and green tea
The nootropic effects of green tea and guarana have been studied by scientists who suggest their potential for improving attention, memory and response time.
Green tea contains several compounds that may affect cognitive function, including L-theanine, catechin and caffeine.
The chemical compounds in the fruit of guarana (Paullinia cupana) include guaranine, the plant’s stimulant substance, which is identical to caffeine. It increases alertness, reduces fatigue and may improve mood.
The current study notes that pure guarana can contain up to 5.3% caffeine compared to espresso coffee and dark chocolate, which have lower contents of around 0.21% and 0.08%, respectively. Additionally, guaranas stimulating effects last longer.
Theobromine in green tea and guarana may have a similar but less potent effect as caffeine.
The current study highlights the potential benefits of green tea and guarana as natural alternatives to drinks that may be excessively high in carbohydrates, caffeine or harmful chemicals.
Study details
The study recruited 33 participants between the ages of 19 and 25 and mostly female from Stefan Cel Mare University in Suceava. They consumed 2 g of guarana daily for 10 days, followed by a 72-hour washout period. Over the following 10 days, they consumed 1.5 g of green tea daily.
Participants chose the consumption method based on recommendations presented before enrollment, mainly preferring the form of an iced tea or shake.
The researchers conducted three cognitive tests before and after consumption of the products, measuring speed, memory and attention. The students also completed questionnaires on perception of health status, product quality and perceived effects.
“The results showed that both guarana and green tea fostered significant improvements in cognitive performance,” the researchers wrote.
Although green tea increased speed and responsiveness for most students, guarana showed a more significant difference in the higher score range than green tea. The researchers found a “strong correlation between cognitive effects and guarana administration, including improvements in energy and retention of information.”
Additionally, more students felt the energizing effect of guarana, while green tea was reported as having an anti-stress and calming effect, providing a feeling of well-being.
The study notes its limitations and calls for further research over extended periods and with larger sample sizes.
Source: Nutrients 2025, 17(6), 1000. doi: 10.3390/nu17061000. “Effects of Guarana and Green Tea Consumption on Students’ Intellectual Performances”. Authors: V. Amaritei et al.