Acute Effects of a Glucose Energy Drink on Behavioral Control Meagan A. Howard and Cecile A. Marczinski Northern Kentucky University There has been a dramatic rise in the consumption of glucose energy drinks (e.g., Amp, Monster, and Red Bull) in the past decade, particularly among high school and college students. However, little laboratory research has examined the acute objective and subjective effects of energy drinks. The purpose of this study was to investigate the acute effects of a glucose energy drink (Red Bull) on cognitive functioning. Participants (N = 80) were randomly assigned to one of five conditions: 1.8 ml/kg energy drink, 3.6 ml/kg energy drink, 5.4 ml/kg energy drink, placebo beverage, or no drink. Participants completed a well-validated behavioral control task (the cued go/no-go task) and subjective measures of stimulation, sedation, and mental fatigue both before and 30 minutes following beverage administration. The results indicated that compared with the placebo and no drink conditions, the energy drink doses decreased reaction times on the behavioral control task, increased subjective ratings of stimulation and decreased ratings of mental fatigue. Greatest improve- ments in reaction times and subjective measures were observed with the lowest dose and improvements diminished as the dose increased. The findings suggest that energy drink consumption can improve cognitive performance on a behavioral control task, potentially explaining the dramatic rise in popularity of these controversial new beverages. Keywords: energy drink, behavioral control, reaction time, stimulation, mental fatigue Since the 1997 debut of the glucose energy drink, Red Bull, in the United States, there has been a dramatic rise in energy drink consumption, especially in adolescents and young adults. The energy drink market grew over 400% between the years 2003 and 2007. Recent estimates value the international energy drink market at $4.8 billion (Mintel, 2008). Energy drinks are marketed as beverages that in- crease physical and mental performance, thus use has be- come widespread among active young people. The absence of regulatory oversight in the United States has resulted in aggressive marketing of energy drinks toward young people for psychoactive, performance-enhancing, and stimulant drug effects (Reissig, Strain, & Griffiths, 2009) and as a mixer with alcohol (Bryce & Dyer, 2007). Adverse health effects of energy drinks have led researchers to state that there are safety issues associated with the use of energy drinks, but this has had little impact on the increasing popularity of these beverages (Clauson, Shields, McQueen, & Persad, 2008). High school and college students have become particularly enamored with the use of these bever- ages. A survey of college students found that reasons for energy drink use included insufficient sleep, to increase energy in general, and to drink with alcohol while partying. Other reasons for drinking energy drinks were to assist in studying and while driving for extended periods of time (Malinauskas, Aeby, Overton, Carpenter-Aeby, & Barber- Heidal, 2007). Energy drinks often contain a variety of ingredients in- cluding caffeine and other plant-based stimulants (e.g., guarana) and amino acids (e.g., taurine). Most researchers concur that caffeine seems to be the main compound that drives the stimulatory effects of these drinks (Ferreira, de Mello, Pompeia, & de Souaz-Formigoni, 2006; McCusker, Goldberger, & Cone, 2006). Caffeine content in energy drinks can range from a modest 50 mg to an alarming 505 mg per serving (bottle or can; Reissig et al., 2009). While the U.S. Food and Drug Administration (FDA) regulates the amount of caffeine found in sodas and other caffeinated drinks and foods, it does not regulate the amount of caffeine in energy drinks. Therefore, regulated foods and beverages can only contain a maximum of 65 mg of caffeine per serving, while a serving of energy drink could potentially contain up to 505 mg of caffeine. For example, Coca-Cola Classic contains only 2.9 mg of caffeine per fluid ounce, while Red Bull contains 9.6 mg of caffeine per fluid ounce (McCusker et al., 2006). Current evidence suggests that moderate doses of caf- feine positively affect cognitive performance. Several as- pects of cognitive performance that show improvement under the influence of caffeine are attention, reaction time, visual search, psychomotor speed, memory, vigilance, and verbal reasoning (Childs & de Wit, 2008; Hewlett & Smith, 2006; Kennedy & Scholey, 2004; Scholey & Kennedy, Meagan A. Howard and Cecile A. Marczinski, Department of Psychological Science, Northern Kentucky University. This research was supported by a Faculty Fellowship from the Kentucky Biomedical Research Infrastructure Network (NIH Grant P20RR016481) and a Faculty Project Grant from Northern Kentucky University, both awarded to Cecile A. Marczinski, and a Summer Undergraduate Research Fellowship awarded to Meagan A. Howard by Northern Kentucky University. Correspondence concerning this article should be addressed to Cecile A. Marczinski, Ph.D., Department of Psychological Sci- ence, Northern Kentucky University, Highland Heights, KY 41099. E-mail: marczinskc1@nku.edu Experimental and Clinical Psychopharmacology © 2010 American Psychological Association 2010, Vol. 18, No. 6, 553–561 1064-1297/10/$12.00 DOI: 10.1037/a0021740 553