There are hundreds of different brands of energy drinks being marketed and their caffeine content per can or bottle ranges from just 50 mg to as much as 505 mg (Weise, 2008). Energy drinks are most commonly consumed by people 11-35 years old (Ballard et al., 2010). Energy drink companies can say anything they want about energy and performance effects of the drinks, and while some energy drinks are banned in some countries, none are banned in the United States (Higgins et al., 2010). High risk behavior has also been associated with consuming energy drinks. Such high risk behaviors include marijuana use, sexual risk taking, fighting, failure to use seat belts, taking risks on a dare, smoking, drinking, problems stemming from alcohol abuse, and illicit drug use (Miller, 2008; Thombs et al., 2009).
Caffeine is the most common ingredient in energy drinks and it is often combined with taurine, glucuronolactone, guarana, and B vitamins to form a type of “energy blend” (Reissig et al., 2009). Most energy drinks contain 70-200 mg of caffeine per 16-oz serving. An 8-oz cup of coffee, in comparison, contains 110-150 mg of caffeine for drip, 40-80 mg for instant, and 50-100 mg for caffeinated beverages (Clauson et al., 2003). While most people experience positive effects from caffeine, like being more awake and alert, adverse effects such as insomnia, nervousness, headache, tachycardia, arrhythmia, and nausea can manifest with an ingestion of more than 200 mg (Calararo et al., 2009; Clauson et al., 2003). With that said, the human body develops a tolerance to caffeine usually three to five days after regular use (Fisher et al., 1986; Robertson et al., 1981).
One of the ingredients in the “energy blend” of an energy drink, the B vitamins, is needed to convert all of the added into energy (Higgins et al., 2010). So the B vitamins are the key to providing the extra energy that the energy drink companies claim their products can provide. Another ingredient in the “energy blend”, Guarana, is a rainforest vine that was domesticated in the Amazon for its caffeine-rich fruits (da Costa Miranda et al., 2009) and its seeds contain more caffeine than any other plant in the world (Smith and Atroch, 2007). A typical 500 mL energy drink also contains about 54 g of sugar, which a little more than ¼ cup (Higgins et al., 2010). The recommended daily allowance for energy drinks is one can, but many people consume more than that.
Several case reports on the negative effects of energy drink ingestion have also been published. Four documented cases of caffeine-associated death have reported, as well as five separate cases of seizures associated with consumption of energy/power drinks (Ballard et al., 2010; Clauson et al., 2003). A healthy 18-year-old man died playing basketball after drinking two cans of Red Bull (Independent, ie., 2007). One case of suspected anaphylaxis was reported (Masuda et al., 2009). An otherwise healthy 28-year-old man had cardiac arrest after a day of motocross racing (Berger and Alford, 2009).
This question relates to Trait 1 since most energy drink consumers are between the ages of 11 and 35 and since energy drinks are targeted toward the young male population. It also relates with Trait 5 being addictive personalities since consumption of energy drinks is often associated with high-risk behaviors like smoking and drinking.
What are the effects of caffeine withdrawal?
Caffeine withdrawal has been studied to find evidence on whether caffeine is addictive or leads to some kind of dependence (Smith, 2002). Headache has been the most frequent outcome measure of the studies, but mood has also been examined (Smith, 2002). An increased reporting of stress caused by caffeine deprivation has been found in heavy coffee drinkers (Ratcliff-Crain et al., 1989). It was also found that caffeine withdrawal was associated with feelings of fatigue and decreased feelings of alertness (Schuh and Griffiths, 1997). Increased depression and anxiety was reported in about 10% of volunteers with a moderate daily intake of caffeine after the caffeine was withdrawn (Silverman et al., 1992).
It has been argued that caffeine has no beneficial behavioral effects but merely removes negative effects associated with caffeine withdrawal (James, 1994). Smith (1995) has a few points arguing against this general view of caffeine effects. It cannot account for the behavioral effects seen in non-consumers, where withdrawal cannot occur, and caffeine withdrawal cannot account for behavioral changes following caffeine consumption after a short period of abstinence or the greater effects of caffeine when arousal is low. Also, claims about the negative effects of caffeine withdrawal require closer examination since they can often be interpreted in ways other than caffeine dependence (e.g. expectancy—Smith, 1996; Rubin and Smith, 1999). This follows from the fact that in most of the studies that have demonstrated increases in negative effect following caffeine withdrawal, the subjects have not been blind but have been told or instructed to abstain from caffeine (Smith, 2002).
A number of studies of caffeine withdrawal and performance concluded that no clear evidence of impaired psychomotor performance associated with caffeine withdrawal was found (Rogers et al., 1995). Other research has also failed to demonstrate negative effects of caffeine withdrawal on performance (Griffiths et al., 1986). So, it can be said that the effects of caffeine withdrawal are restricted to mood and that performance is unaltered (Comer et al., 1997).
This question about caffeine withdrawal can be tied into Trait 2 about stress and anxiety. A career business professional who is a habitual caffeine drinker probably feels that they need the caffeine just to get through the day. If they suddenly don’t have any caffeine, then they can start feeling that stress and anxiety come out until they can consume some more caffeine.
What effects does habitual caffeine use have on memory, attention, planning capacity, and psychomotor performance?
It has been found that acute caffeine intake, even amounts as low as 32 mg, (Leiberman et al., 1987) can improve reaction times (Jacobson and Edgley, 1987; Swift and Tiplady, 1988) and performance on vigilance tasks (Yu et al., 1991). Whether caffeine intake has an impact on memory or not is more of a debate. Some authors have found that an intake of 100 mg of caffeine improved memory function (Terry and Phifer, 1986) while others found that intakes of 125 mg and 250 mg had no effect (Foreman et al., 1989; Mitchell and Redman, 1992). Another factor that is unclear is whether or not caffeine intake has an effect on attention. One study showed that ingestion of 125 mg and 250 mg of caffeine impaired attention (Foreman et al., 1989) and another study showed that it had no effect (Edwards et al., 1996). In these studies attention was measure by the Stroop Test, which is a test with three different subtasks displaying 10×10 items (Nehemkis and Lewinson, 1972) involving colors and words of colors.
Sensitivity to habitual caffeine consumption has been shown to vary among different age groups. A study performed on three age groups showed that acute caffeine intake improved performance of a memory task only in the middle-aged participants. The authors conjectured that these results where due to the fact that caffeine was habitually consumed twice as much by the middle-aged participants than by the younger and older participants (Hogervorst et al., 1998). Better performance on a reaction-time task was significantly related to higher caffeine levels, but this improvement was greatest in the older participants (Jarvis, 1993). The results of these studies, along with other studies, suggest that habitual caffeine consumption may have beneficial effects on age-related cognitive decline (Hameleers et al., 2000).
The study completed by Hameleers, Van Boxtel, Hogervorst, Riedel, Houx, Buntinx, and Jolles (2000) involved performing cognitive tasks on participants from different age groups to measure memory function, reaction time, planning capacity, and attention. Before the tests participants had to complete a questionnaire that asked about their daily caffeine consumption. They were also offered a cup of coffee or tea to make sure that they maintained normal caffeine levels and so there would not be potential for withdrawal effects (Hameleers et al., 2000).
The results of the study showed that faster movement time was associated with higher daily caffeine consumption, habitual caffeine consumption was positively related to delayed recall performance, and there was a quadratic relationship between habitual caffeine consumption and simple reading speed in that it improved up to a certain point and then decreased (Hameleers et al., 2000). Higher habitual caffeine intake was found to be associated with better long-term memory and faster simple response speed, but was not significantly associated with short-term memory performance, planning capacity, information processing, or attention (Hameleers et al., 2000). This study did not find any differences in sensitivity to habitual caffeine consumption between different age groups on the cognitive test performance (Hameleers et al., 2000).
The results that caffeine effects memory only on middle-aged people follows closely with Trait 1 since most career business professionals are in this age range. Trait 3 could also tie into this since being more alert and having a better response speed can help with multitasking. How does caffeine effect memory recall?
Caffeine is a mild CNS stimulant that increases arousal (Nehlig et al., 1992) and acute caffeine ingestion increases the extracellular levels of acetylocholine (Carter et al., 1995). These neurotransmitters are involved in memory and locomotor activity and chronic caffeine consumption leads to an increase in adenosine receptor numbers (Hameleers et al., 2000).
Does a pre-existent expectancy of caffeine have an effect on performance?
Caffeine has been found to improve vigilance and psychomotor performance (Rees et al., 1999; Wesensten et al., 2005) and also to increase levels of information processing and performance on working memory tasks, (Elliman et al., 2010) but it is possible that pre-existent expectancy may play a factor in these improvements. Since there is evidence that some of the effects of alcohol, glucose, and nicotine can be linked to expectancy (Elliman et al., 2010), caffeine has also been studied for expectancy effects. One study found that the expectancy related effect of caffeine on attention and memory scanning was dependant on whether participants had pre-held beliefs regarding the stimulant effects of caffeine (Oei and Hartley, 2005). In the study done by Elliman*, Ash, and Green (2010), participants were given coffee on four different occasions. On two of the occasions they were given caffeinated coffee, one of which they were told it was decaffeinated, and on the other two occasions they were given decaffeinated coffee, one of which they were told was caffeinated. After ingestion of the coffee on each occasion, mood and vigilance performance were assessed (Elliman et al., 2010). Fisher’s LSD test indicated that when participants were given caffeinated coffee and were accurately informed that it was caffeinated, they scored significantly more correct hits than in the other three conditions (Elliman et al., 2010). In the self-reported mood analysis participants reported higher levels of anger and hostility when given decaffeinated coffee but were told it was caffeinated (Elliman et al., 2010). Also, the depression scores were lower in both conditions during which participants were given caffeinated coffee (Elliman et al., 2010). Participants performance on the Bakan vigilance task was better after they had caffeinated coffee and were told that it was caffeinated than when they had caffeinated coffee and were told it was decaffeinated (Elliman et al., 2010). Expectancy had no significant effect on task performance when the participants were given decaffeinated coffee (Elliman et al., 2010). The main results of this study showed that performance on a computer based measure of sustained attention was significantly affected by pre-existing expectancy regarding whether participants had been given caffeinated or decaffeinated coffee, but this effect was only observed in the two conditions where participants were actually given caffeinated coffee (Elliman et al., 2010). Expectancy had no effect when decaffeinated coffee was administered (Elliman et al., 2010). There were no clear effects of expectancy on self-reported mood (Elliman et al., 2010). The data suggest that caffeine does exert a beneficial effect on cognitive function but that is arbitrated by expectancy concerning the nature of the effects of caffeine on performance (Elliman et al., 2010).
Expectancy can relate to Trait 4 if someone really thinks they need caffeine to get something done and they know that it will help them get it done. This preconceived notion that the caffeine will help them is where the expectancy comes in.