It's been a grind all day and now it's bedtime — but you've got more work to do. Should you gulp an energy drink? "Gulp" is the operative word, health experts say. Ounce for ounce, most energy drinks may be no worse for health than strong coffee. But while people sip a coffee or tea, those who choose energy drinks consume them like soda pop.
And look at the packaging: Monster Energy, for example, comes in a 16-ounce can, which is technically two servings' worth of caffeine, and youth researchers say many teens will drink the whole thing.
Energy drinks are the fastest-growing segment of the beverage industry, with sales rising about 9 percent by volume in 2010 and growing at the same pace this year, according to John Sicher, editor and publisher of Beverage Digest.
"I'm going to be on a bus to Lansing (Mich.) and I'll miss my afternoon coffee, so I'll have one of these," says Dennis Wixon, 27, of Sterling Heights, Mich., while buying two bottles of 5-Hour Energy at a service station in Warren, Mich., last week.
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Others turn to them because coffee isn't enough.
"This might be strange to say, but caffeine doesn't give me that kick anymore — it's almost a necessity," says Oakland University junior Kaitlyn Chornoby.
Chornoby, 20, of Shelby Township, Mich., said she drinks some coffee and Mountain Dew, but usually it's an AMP: Focus or Monster energy drink.
Researchers say caffeine abuse is widespread among adolescents and college students, who use energy drinks to overcome a lack of sleep or to stay up cramming for exams.
Energy drinks have other ingredients with unproven effects, such as high doses of vitamins and other nutrients, tied to label claims of increased concentration and an energy kick.
"The other stimulants in these drinks are not as well understood as caffeine, and the data is mixed" about whether they boost alertness, says Joe Carlson, a Michigan State University youth nutrition researcher.
Moderation is key
Nutrition experts say that healthy adults who otherwise would drink coffee or tea can switch to energy drinks as long as they don't overindulge.
"It's just a beverage that can replace your cup of coffee in the morning," says science policy chief Maureen Storey at the trade group American Beverage Association.
But you'd be better off with coffee or tea, says David Schardt, senior nutritionist at the Center for Science in the Public Interest, a research group begun by Ralph Nader.
"If you need to stay alert and, for some reason, don't want coffee, an energy drink will do the trick. If you're driving, it might even save your life," Schardt says. But unless energy drinks are labeled low-calorie, "they're sugary, caloric drinks, and that can add up" to weight gains, he says.
Coffee and tea have no calories until you add sugar and milk or cream.
Who should avoid energy drinks?
Energy drinks are being increasingly abused, especially by young people hooked on caffeine, according to the American Association of Poison Control Centers. The organization, which began tracking energy drink incidents this year, received 340 reports of adverse health effects caused by the drinks' high caffeine levels.
People with high blood pressure or heart disease also should beware of caffeine, says James Kalus, senior pharmacy manager at Henry Ford Hospital in Detroit.
In a study the hospital published in 2008, Kalus found that healthy volunteers had about a 10 percent increase in blood pressure and pulse rate after being put on a regimen of two energy drinks a day.
Ready-mixed combinations, in brands like Four Loko, Joose and Smirnoff Raw Tea, were banned in Michigan last fall, although college students still consume their own mixtures, says Joe Carlson, a Michigan State University youth nutrition researcher.
Because caffeine masks the depressant effects of alcohol, people who mix energy drinks and alcohol feel less intoxicated than they actually are.
"The net effect is that people end up consuming a lot more alcohol than they would," says Robert Brewer, an alcohol program leader with the Centers for Disease Control in Atlanta.
Such drinkers are "actually just as impaired as if they hadn't had the caffeine," but they don't feel as drunk, Brewer says.
Comparing caffeine content
Starbucks Grande coffee (16 oz.) 330 mg.
Dunkin' Donuts regular coffee (14 oz.) 178 mg.
Rip It F Bomb energy drink (16 oz.) 210 mg.
Mojave Rattler Venom energy drink (16.9 oz.) 170 mg.
AMP Overdrive energy drink (16 oz.) 160 mg.
Monster energy drinks (16 oz.) 160 mg.
Red Bull energy drink (12 oz.) 114 mg.
Excedrin Extra Strength (2 tablets) 130 mg.
Anacin Maximum Strength (2 tablets) 64 mg.
Mountain Dew (12 oz.) 54 mg.
Dr Pepper (12 oz.) 42 mg.
Pepsi, most types (12 oz.) 38 mg.
Coca-Cola, most types (12 oz.) 35 mg.
Hershey's Special Dark Chocolate bar (1.5 oz.) 33 mg.
Ben & Jerry's coffee ice cream (8 oz.) 68 mg.