Energy drinks are canned or bottled beverages sold primarily in convenience stores, and grocery stores, and bars and nightclubs (in mixed drinks). Most energy drinks are carbonated drinks that contain large amounts of caffeine and sugar with additional ingredients, such as B vitamins (e.g., niacin, pyridoxine and cyanocobalamin), amino acids (e.g. taurine), ginseng, and herbal stimulants such as guarana, a South American herb that is an additional source of caffeine.
“Most of the performance-enhancing effects of energy drinks can be linked to their caffeine content,” says Stephanie Ballard, PharmD., assistant professor of pharmacy practice at Nova Southeastern University’s West Palm Beach campus.
Red Bull, one of the most popular energy drinks, contains nearly 80 mg of caffeine per can, about the same amount of caffeine as a cup of brewed coffee and twice the caffeine as a cup of tea. Other energy drinks contain several times this amount.
“Caffeine has been consistently been observed to enhance aerobic performance, although its effects on anaerobic performance may vary.”
Ballard and colleagues Jennifer Wellborn-Kim, PharmD., and Kevin Clauson, PharmD., authored a paper, Effects of Commercial Energy Drink Consumption on Athletic Performance and Body Composition, in a recent issue of The Physician and Sportsmedicine.
“There is conflicting evidence of the impact of energy drinks on weight loss,” Ballard adds, “although some data suggest that combining energy drink use with exercise may enhance body fat reduction. Increases in burning calories and losing weight are likely subject to diminishing returns as users become habituated to caffeine. “
Don’t forget these drinks are often loaded with sugar, she adds. “Despite their use for weight loss, energy drinks may be contributing to the obesity epidemic alongside less caffeinated, sugary drinks like soda.”
The amount of caffeine in an energy drink isn't always indicated on the label, so it is difficult to gauge how much one is consuming.
Red Bull-swilling athletes should be aware of the caffeine limitations of sports governing bodies, as well as the risks to their health.
“Although caffeine was removed from the World Anti-Doping Agency’s prohibited list in 2004, it is still followed under the 2009 Monitoring Program to identify patterns of misuse,” says Ballard. “For the National Collegiate Athletic Association, athletes are considered to be doping if urinary caffeine is greater than 15 µg/mL, which is about the same as drinking eight cups of coffee, each containing 100 mg of caffeine.”
As with any active substance, energy drink ingredients may cause adverse effects, particularly with high episodic consumption, warns Ballard. And these energy drinks, which are classified as dietary supplements, are in a regulatory gray area, allowing them to sidestep the caffeine limitations assigned to foods and soft drinks.
“The FDA limits caffeine in soft drinks to 71 mg/12 fluid oz,” says Ballard. “But energy drinks can contain as much as 505 mg of caffeine in a single container – the equivalent of drinking 14 cans of Coca-Cola. Caffeine has been reported to cause insomnia, nervousness, arrhythmias, osteoporosis, cardiovascular disease, pregnancy and childbirth complication, gastrointestinal upset and death.”
One of the biggest concerns is that we just don't know enough about the effect of the combination of ingredients in energy drinks. Many ingredients are believed to work synergistically with caffeine to boost its stimulant power. For instance, one can of Red Bull contains 1000 mg of taurine. A German double-blind study compared a taurine and caffeine drink, a caffeine-only drink, and a placebo drink. Stroke volume--the volume of blood ejected with each beat of the heart--was increased only in the group taking the taurine-and-caffeine drink. Taurine appears to play an important role in muscle contraction (especially in the heart) and the nervous system.
But small amounts can be safe and still boost performance. “Caffeine in amounts of up to 6 mg/kg may produce benefits with low risk of adverse effects,” says Ballard.