Can roasted green tea boost cognitive performance?

Green tea, in particular, is consumed worldwide as a healthy drink because of its characteristic inhibition of cholesterol absorption by the body through tea catechins, as well as its antioxidant and antibacterial effects. Previous research has highlighted the cognitive benefits of green tea consumption, though the research has often focused on long-term effects, individual compounds in isolation, or high consumption.

The study involved 20 healthy adult men aged around 23. They underwent a mental arithmetic task six times over two sessions in one day. In the first session, they drank hot water before three tasks and then had a rest, repeating four times. In the second session, they consumed either green tea or roasted green tea before the remaining tasks and another rest, also four times. This process was repeated a month later, with participants trying both teas. Researchers assessed 11 physiological responses and gathered self-evaluations on fatigue, stress, mental workload, and workflow to gauge the effects of hot water and different teas on mental performance.

The results revealed that compared to drinking hot water, tea consumption during tasks resulted in significantly lower tissue blood volume (TBV), tissue blood flow (TBF), and near-infrared spectroscopy responses (NIRS) in participants. Aromatic compounds present in green tea, known to have relaxation effects, appeared to play a significant role in these positive outcomes.

The findings suggested that drinking green tea or roasted green tea may help moderate the participants’ physiological stress responses. Through examining the multiple indicators, aromatic stimulation from tea drinks suggested the potential to exert positive physiological and subjective effects in a short duration and in small quantities, similar to amounts consumed daily.

“The study highlights the role of aromatic stimulation from tea, particularly compounds like pyrazines in roasted green tea, in influencing mood, relaxation, and alertness by directly affecting brain activity. Additionally, tea consumption induces peripheral vasoconstriction, potentially contributing to feelings of refreshment and increased alertness,” said Alyssa Simpson, registered dietitian and medical nutrition advisor.

Reference: Kurosaka, C., Tagata, C., Nakagawa, S. et al. Effects of green tea and roasted green tea on human responses. Sci Rep 14, 8588 (2024). https://doi.org/10.1038/s41598-024-59383-y