Energy drinks enhance prefrontal cortex activity during a calculation task: modulation by individual eating habits

• We aim to clarify the effect of energy drinks on the activity of the medial prefrontal cortex (MPFC) during calculation tasks. • The calculation time was shortened by energy drink intake without a change in the concentration of cortisol. • MPFC activity varied among the participants; it increased in one and decreased in others. • The participants with an increased MPFC activity following energy drink intake frequently drank milk and less frequently ate cakes. • The effect of energy drinks on MPFC activity during calculation tasks modified the activity of the left dorsolateral prefrontal cortex and shortened the calculation time, and it potentially varies depending on the eating habits. Several energy drinks (EDs) are sold worldwide and many young adults frequently drink them, who believe that EDs give them increased energy and improve their performance in tasks. However, their effect on brain activities is controversial. In this study, we aim to clarify the effect of EDs on brain activities, especially the activities of the medial prefrontal cortex (MPFC) and dorsolateral prefrontal cortex (DLPFC), by functional near-infrared spectroscopy during calculation tasks. We found that the calculation time was shortened after ED intake. We also found that 1) the activity of MPFC was significantly correlated with the amount of ED drank, 2) the activity of MPFC was significantly correlated with the activity of the left DLPFC (LDLPFC), and 3) the activity of LDLPFC significantly correlated with the calculation time after ED intake. Moreover, we found that the activities of MPFC and LDLPFC varied among the participants and the participants, with an increased MPFC activity following ED intake frequently drank milk. We concluded that the effect of EDs on prefrontal cortex activity during calculation tasks is limited and potentially varies depending on the frequency of food intake.