This is an excerpt from Caffeine for Sports Performance.
Mixing Energy Drinks and Alcohol
Athletes normally are very disciplined people who carefully plan most aspects of what they do. But they also need downtime and like to party as much as (and sometimes more than) other people. The relationship between alcohol and caffeine used to be the search for a strong coffee brew as a pick-me-up after a late night of drinking or as an aid to sobering up. Now, however, it is common, especially among young people in party situations, to consume caffeine-containing products while they are consuming alcohol. In some countries, the combination of alcohol and caffeine exists in commercial products. However, the more typical scenario involves the self-mixing of energy drinks with alcoholic beverages such as spirits. The idea is that the uplifting and arousing effects of the energy drink counteract the depressant effects of alcohol, although in some cases people use the energy drinks to disguise the taste of the alcohol. Decreasing the subjective perceptions of being intoxicated may deliberately or inadvertently allow drinkers to increase their alcohol consumption.
The numerous constituents in energy drinks, such as taurine, ginseng, amino acids, inositol, ribose, and choline, have generally failed to show any active effects. This leaves the ingredients of interest in energy drinks as carbohydrate and caffeine. On the surface it may look as though an energy drink is optimal for energizing the muscles and the brain with its high carbohydrate content (9-15 g per 100 ml) and caffeine boost of 50 to 120 mg per serving. However, although the amount of caffeine added to many energy drinks is low to moderate and stated on the label, the total caffeine content of some drinks may not be specified due to the inclusion of other caffeine-containing compounds such as guarana, yerba maté, and kola nuts. The real concern comes when energy drinks are consumed in large volumes, which can easily happen if the athlete is determined to have a big session with alcohol and uses energy drinks as a mixer or chaser. There is already much concern regarding the dangers of excessive consumption of energy drinks due to their caffeine content, but the interaction with alcohol adds another dimension.
The literature is full of reports documenting the use of energy drinks along with alcohol. For example, studies from various countries have reported that 54% (United States), 25% to 40% (France), and 40% (Turkey) of college students consumed energy drinks with alcohol while partying, with many users reporting that they consumed at least three servings during the partying episodes (United States). The worry is that this type of behavior leads to a greater predisposition to alcohol dependence. However, a recent study from the Netherlands argues that a personality trait with higher levels of risk-taking behavior may be the primary reason for increased alcohol and drug abuse and that the co-consumption of energy drinks with alcohol is simply an expression of that type of lifestyle and personality. However, given the high prevalence of the co-consumption in young people, this explanation seems unlikely to account for the majority of people exhibiting this behavior.
Read more from Caffeine for Sports Performance by Louise Burke, Ben Desbrow, and Lawrence Spriet.