On The Early Show Monday, nutritionist Samantha Heller said the word "energy" in the description of many of these drinks is really a euphemism for "calories."
Heller, a senior clinical nutritionist at NYU Medical Center and contributor to Health magazine, told co-anchor Rene Syler, "We're looking for a smoking gun to find that caffeine is bad. Actually, caffeine has some benefits. It can improve your mood, your cognition, memory, and feeling of well-being, and helps alleviate fatigue. There are times when that's necessary.
"But too much is not good, and too much is going to vary among individuals — because caffeine is addictive and we build up tolerance to caffeine.
"Too much can increase anxiety, cause poor sleep. Your motor skills can decline. It can increase your heart rate, your blood pressure. People with recent cardiac events or high blood pressure or other medical conditions have to be careful, and it can interfere with some medications.
"Some people really suffer when they try to kick coffee. They may feel nauseous, have headaches. Sometimes withdrawal can be very uncomfortable."
The $3.4 billion market for energy drinks grew by 80 percent last year.
Heller pointed out that eight ounces of Red Bull, a popular energy drink, contain about 80 grams of caffeine — about the same as a cup of coffee.
"Most people will drink whole cans (even though each can may contain two or three servings)," Heller noted. "So, you are getting two to three times the caffeine and calories that the label says."
The drinks are very popular with young people. But Heller says, "I just don't think kids need to be drinking caffeine at any age. Maybe I could say 16 is fair, but caffeine is addictive and can contribute to poor sleep, and to hyperactivity in children. We don't want them drinking these energy drinks in place of healthy foods. Some kids are using them for weight loss, which of course we don't want. And kids and adults are using them to boost their athletic performance, and that could lead to dehydration and injury."
Heller is especially concerned about mixing the energy drinks with alcohol: "It's very dangerous. Alcohol is a depressant. Caffeine is a stimulant. You're mixing them together. You're gonna feel less impaired than you are, so you might drive when you're over-intoxicated. You may drink more alcohol than your system can handle. And, apparently, emergency room visits with kids with alcohol poisoning are increasing, partly because of this mixture. You have to be very careful."