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Introduction Energy drinks are promoted as enhancing behavioral outcomes by reversing fatigue effects and consequently increasing alertness and endurance (Hickman, Sherry, & De Mejia, 2010). Ingredients may include caffeine, terrine, acculturation, sugars, and other B vitamins and herbal extracts. Despite the range of constituents, researchers generally claim caffeine as the core ingredient responsible for the stimulatory effects of energy drinks (Resign, Strain, & Griffith, 2009).
However, recent research has suggested a synergistic interplay between energy drink institution, with greater performance benefits conferred by the whole beverage than expected from the caffeine content alone (Markings et al. , 2011 and Schools and Kennedy, 2004). For example, Schools and Kennedy (2004) reported that energy drink consumption improved performance on ‘secondary memory and ‘attention speed’ factors relative to placebo, with no significant improvement in performance following independent caffeine ingestion.
However, Schools and Kennedy (2004) note that independent caffeine effects may have been detected with increased power, articulacy in light of the small sample size used in this exploratory study (N = 20). Consequently, further systematic analysis of the independent and interactive effects of energy drink constituents is required before conclusions are drawn regarding their relative efficacy.
One core energy drink ingredient which lacks such scrutiny is terrine (2-amphetamine colophons acid), an abundant free amino acid widely- distributed throughout the body and readily found in animal-derived dietary sources (Finnegan, 2003 and Washable, 1992). Despite advertising claims of enhanced alertness post-energy drink consumption, and marketing of terrine as a key energy drink ingredient, there is a dearth of research regarding terrine’s behavioral impact (Australia New Zealand Food Authority, 2001 and Finnegan, 2003).
Caffeinated terrine drink consumption has generally resulted in significantly shorter mean reaction times on attention tasks relative to placebo and control beverages (Renee and Horny, 2002, Aside et al. , 2000 and Warburton et al. , 2001). However, the presence of other psychoactive ingredients (e. G. , glucose) in the beverage has confounded inferences grading terrine’s independent and interactive effects on behavioral performance.
For example, Chills and De Wit (2008) reported significantly faster simple and choice reaction time following ingestion of a caffeine-containing supplement (200 MGM) relative to placebo. While the authors attributed these outcomes to the caffeine content, they noted that capsules contained terrine (10 MGM) in addition to other active ingredients (50 MGM white willow bark and 30 MGM magnesium oxide). Similarly, Aside et al. (2000) reported enhanced performance on a auditory oddball task following caffeine and terrine consumption.
While placebo administration resulted in significantly longer reaction time relative to baseline, there was no significant difference in reaction time after co-administration of terrine (1000 MGM) and caffeine (80 MGM) relative to baseline. However, the capsules contained acculturation (600 MGM), another primary energy drink ingredient. The absence of comparative independent administration conditions in these studies have precluded any whether outcomes are driven by one substance or the combination of substances.
To our current knowledge, there has only been one study specifically assessing the independent and combined effects of caffeine and terrine on behavioral performance. Giles et al. (2012) reported significantly faster simple and choice reaction time following active (200 MGM) relative to placebo caffeine consumption, with no independent effect of terrine (2000 MGM) or interactive effect of terrine and caffeine evident for reaction time. However, the quantity of caffeine and terrine in a standard energy drink is typically less than the administered doses, with approximately 80 MGM caffeine and 1000 MGM terrine per 250 ml serving.
Consequently, the aim of the present study was to determine the independent and combined effects of two primary energy drink ingredients, caffeine and terrine, on behavioral performance, specifically reaction time. Based on previous research assessing the effects of caffeine and energy drinks on attention (e. G. , Loris et al. , 1994 and Aside et al. , 2000), an oddball task and a stimulus degradation task were selected to assess behavioral performance. Caffeine (80 MGM) and terrine (1000 MGM) doses were matched to the typical content of a standard 250 ml energy drink serving to increase the generalizations of results.