Energy drinks are exploding in popularity, and there seems no end in sight to the remarkable growth of this billion dollar industry. According to BevNET (, which publishes product reviews for the beverage industry on the Web, more than 300 brands exist, including some from major food companies. Costing about $2 for a typical 8.3-oz can, the beverages are relatively expensive compared to soft drinks and bottled water, and have high profit margins.

Energy drinks promise not only quick energy and more physical endurance but also better reaction times, increased concentration, and improved mental alertness. Typically targeted to males under age 30, some products even claim to boost the libido (Wright, 2005).

Many brands have evocative names and logos, and are sold in dance clubs, health and convenience stores, and over the Internet. They are regulated as either a conventional food or a dietary supplement by the Food and Drug Administration, depending on whether the manufacturer uses a Nutrition Facts or Supplement Facts panel.

Typing energy drink into Google will yield more than 20 million results, considerably more than you get for either bottled water or soft drink. But it’s doubtful you will locate any science-based evidence among these Web sites suggesting that these products deliver on their marketing claims.

The only constituent in energy drinks that actually has an ergogenic (energy-enhancing) effect is caffeine (Pasman et al., 1995), which is often added at levels similar to that of coffee (75–85 mg/8 oz). Many products also contain guarana, another source of caffeine derived from the seeds of an Amazonian shrub. Although the total caffeine content may therefore be quite high, the actual amount is not required to be listed on the label. There usually is a warning, however, advising that the product is not recommended for persons sensitive to caffeine.

Individuals are known to vary widely in their sensitivity to caffeine, a central nervous system stimulant. The acute effects of caffeine include rapid heart rate, hypertension, and tremors, and guarana has been linked to a case of fatal cardiac arrhythmia (Cannon et al., 2001). Moreover, caffeine’s diuretic effect can exacerbate the loss of fluids through sweating, so energy drinks may increase the risk of dehydration during exercise. These and other concerns have prompted some European countries to ban or restrict sales of high-caffeine energy drinks.

Some energy drinks also have warnings not to mix them with alcohol, since there are inherent risks in combining stimulants with depressants. However, this combination seems to be a popular practice, especially in bars and nightclubs where energy drinks are often sold.

The main source of energy (calories) in energy drinks is sugar, in its various forms. There are no credible studies showing that other common ingredients—taurine, glucuronolactone, ginseng, ginkgo, inositol, L-carnitine, and antioxidants—are capable of boosting energy, enhancing vitality, or providing any of the other claimed benefits. Taurine, an amino acid abundant in many foods, will not boost your stamina but it might give your cat more pep, since felines need it.

Glucuronolactone is a cellular metabolite naturally produced by the body. One energy drink company states that this ingredient “is widely known to improve mental performance, reaction time, concentration, and memory,” but no data exist to back this claim. Similarly, there is no evidence that the herbs in energy drinks have any benefits. Moreover, the safe upper limits, potential interactions, and long-term effects of some of these ingredients have not been adequately investigated.

Energy drinks often have a “gimmick.” For example, some tout the virtues of certain flavonoids (such as quercetin or catechins) while others claim to “detoxify” your body. One brand boasts an enzyme blend to “help you absorb (the product) more efficiently.” Never mind that these enzymes are present in trivial amounts, are inactivated during digestion, and have no substrate—two are actually misspelled on the label.

In conclusion, energy drinks are all about marketing hype. There is scant evidence that the products function beyond the effect of caffeine, and the risks associated with their use are unclear. The promises made today for energy drinks have not changed very much from those of the tonics and elixirs hawked by snake oil salesmen in the 19th century.

by Mark A. Kantor,
Associate Professor 
Dept. of Nutrition & Food Science, Univ. of Maryland 
[email protected]


Cannon, M.E., Cooke, C.T., and McCarthy, J.S. 2001. Caffeine-induced cardiac arrhythmia: an unrecognised danger of healthfood products. Medical J. Australia 174: 520-521.

Pasman, W.J., van Baak, M.A., Jeukendrup, A.E., and de Haan, A. 1995. The effect of different dosages of caffeine on endurance performance time. Int. J. Sports Med. 16(4): 225-230.

Wright, R. 2005. Nutraceutical beverage update. Nutraceuticals World 8(9): 32-48.