Despite a recent spate of bad press, the popularity of energy drinks has not waned. Energy drinks and shots represent a $9 billion business in this country, and the category has been growing consistently since Red Bull introduced the first such product in 1987. Domestically, Red Bull alone is a $3 billion brand, and the leading energy shot product, 5-hour ENERGY, boasts $1 billion in retail sales. A 2011 study published in the journal Pediatrics reported that 30 to 50 percent of teens and young adults use energy drinks and that people under the age of 25 account for half of all sales. Teen and young adult males are reportedly the leading consumers of energy drinks.
To answer this question, I offer a breakdown of the most common energy drink ingredients and the science behind them.
• Caffeine: The one thing all energy drinks and shots have in common is caffeine, though you may not always see it listed on the label as such. While chemically-derived caffeine will be listed explicitly on a label, the natural caffeine contained in ingredients like guarana, green coffee extract, green tea extract, or yerba mate may not be. According to the aforementioned study, beverage marketers are not required to list the naturally-occurring caffeine content in these ingredients. That means that even listed caffeine levels may be under-reported if they are included in addition to synthetic caffeine. Importantly, "natural caffeine" is chemically identical to the stuff produced in a lab. As a result, it behaves no differently in the body and produces identical results; it is neither more "healthy" nor less so.
Caffeine is a known nervous system stimulant, and it has been associated with outcomes ranging from improved performance among endurance athletes to faster reaction times in problem solving. While we may equate the physical and mental "second wind" we get from caffeine with "energy," it is more accurate to say that caffeine provides alertness. (More on this distinction later.) There is a fairly robust body of research examining the effects of energy drinks on exercise endurance, cognitive performance, memory, and alertness. The consensus is that essentially, most—if not all—observed benefits of energy drinks in these areas can be attributed to the caffeine content alone.
It's also worth noting that a calorie-free "energy drink" would be more accurately called an "alertness drink," as it relies on caffeine (or the placebo effect) to produce the desired effects of increased mental stamina rather than actual, usable energy for the brain and body.
• Sugar: In the most literal sense of the word, "energy" is the ability to do work. In the context of our bodies, the ability to do work translates into the ability of muscles to contract, and of cells, tissues, and organs to carry out the day-to-day business of metabolism. Only calories can provide the fuel for this ability to function; no amount of vitamins, minerals, or caffeine can serve this purpose. And the easiest, most direct form of energy to fuel the body comes in the form of carbohydrates. Indeed, the brain alone requires about 120 grams of carbs per day as its preferred energy source.
Sugar is the carb of choice in most energy drinks—often in the forms of quickly-absorbed sucrose and glucose. Some complain that these formulations result in a so-called "energy-crash" in the hours following use. This would result from a rapid spike in insulin levels to respond to the quick sugar infusion, which can sometimes be followed by a rebound effect of excessively low blood sugar levels.
In their new book, Willpower, Roy Baumeister and John Tierney document the fascinating science behind low blood sugar levels and their correlation with a range of outcomes, including poor decision-making ability, mental fatigue, impaired anger management, criminal behavior, and even excessive spending. It's hardly surprising then that most energy drinks contain a carbohydrate as quickly and easily assimilated as sugar.
• B vitamins: Megadoses of B vitamins—particularly B12—tend to feature prominently in energy drinks. Often, these nutrients are credited with providing energy, burning fat, or speeding up metabolism, though in fact, they do none of these things.
For starters, vitamins do not supply energy (they have no calories), nor do they contribute to alertness. Using my least favorite analogy for energy metabolism—the car—one can think of the B vitamins as air in the internal combustion engine. Air aids the conversion of fuel into usable energy, but it provides no actual energy itself. Additional B vitamins don't speed up metabolism, nor do they make you burn more energy than you otherwise would. Dietary requirements of the B vitamins are quite low, and they are widely found in the food supply—particularly in the diets of the heaviest users of energy drinks (young males). Whatever excess you take in, you just pee out. For all these reasons, I'd venture to say that these vitamins deliver little to nothing by way of an "energy benefit"; they're cheap to include, even at high levels, and are essentially there for show.
• Taurine: Taurine is a compound derived from amino acids (protein building blocks) that we humans can manufacture on our own. Although we get most of it from our diets, taurine is widely available in animal-derived foods such as fish, shellfish, meat, and dairy.
Possible benefits of supplemental taurine are still being investigated, though the limited data available suggest a possible role in lowering cholesterol and controlling high blood pressure. However, these results appear to be associated with substantially higher doses than those found in a typical energy drink. More importantly, studies have shown that the combination of caffeine and taurine in energy drinks actually seems to produce an increase in both blood pressure and heart rate—likely an effect of the sugar and caffeine. My takeaway? Taurine provides no substantive physiological or cognitive benefit in an energy drink.
If you find your energy flagging in midday, my advice is to try something called a snack. Half of a tuna sandwich on whole grain bread and a cup of plain coffee will deliver your caffeine and the type of energy-yielding carbs that won't spike and crash your blood sugar. And for those who insist on taurine and vitamin B12, it's even a good source of those as well!
Hungry for more? Write to firstname.lastname@example.org with your questions, concerns, and feedback.
Tamara Duker Freuman, MS, RD, CDN, is a NYC-based registered dietitian whose clinical practice specializes in digestive disorders, Celiac Disease, and food intolerances. Her personal blog, www.tamaraduker.com, focuses on healthy eating and gluten-free living.