Recently, several caffeine-containing beverages, that is, energy drinks, have been sold worldwide (Beckford et al., 2015). They are promoted as drinks to support active/busy people who need an “extra boost” or wish to “sake off grogginess” (Garcia-Alvarez et al., 2020). The components of energy drinks are mainly caffeine, taurine, carnitine, B complex vitamins, and guarana (Costantino et al., 2023). Caffeine can produce subjective reinforcement and discriminant stimuli via dopamine (Garrett et al., 1997, Ferré 2016), and guarana in energy drinks plays the same role (Scholey and Haskell, 2008). Taurine contributes various physiological functions such as neuromodulation, cell membrane stabilization, and the regulation of intracellular calcium levels (Timbrell et al., 1995). Carnitine and B complex vitamins are particularly support mitochondrial activity and energy production (Belay et al., 2006, Williams et al., 2004).
However, the effect of energy drinks on human performance is controversial (Garcia-Alvarez et al., 2020). It has been reported that energy drinks improve the performance during reaction-time, tapping, executive function (reaction time plus tapping) tasks, and cognitive performance (Pomportes et al., 2019, Lassiter et al., 2012, Oliver et al., 2021). It has also been reported that adolescent males feel that energy drinks are effective (Temple et al., 2011) and they consume more than adolescent female (Yamasaki et al., 2023). However, excessive consumption of energy drinks induces arrhythmia and cardiovascular diseases, which may cause sudden death, sleep disorders and anxiety, hepatitis, and acute kidney injury (Costantino et al., 2023). Moreover, it has also been shown that energy drinks are not efficacious in increasing energy levels nor any related cognitive or behavioral variables measured (Garcia-Alvarez et al., 2020).
In this study, we aim to clarify the effect of energy drinks on brain activity, especially medial prefrontal cortex (MPFC) and dorsolateral prefrontal cortex (DLPFC) activities, during calculation tasks. MPFC connects several brain regions and it affects the cognitive processes of other cortical regions as a band-path filter during action and response perception (Cohen, 2011; Harper et al., 2017; Miller and Cohen, 2001; Price, 1999). DLPFC also plays an important role in decision-making, working memory processes, and updating and manipulating task-relevant information (Gauselmann et al., 2022, Owen et al., 2005, Rottschy et al, 2012, Dantas et al., 2023). Thus, the effect of energy drinks on calculation task performance could be detected in these areas.
We found that the intake of energy drinks mainteined the activity of MPFC during calculation tasks and shortened the calculation time. Changes in the activity of MPFC via energy drink intake are potentially affected by food (cakes and milk) intake frequency.