Ever since Red Bull took the beverage industry by storm in 1987, drinks such as Monster, Full Throttle, Rock Star, No Fear, Amp and Adrenaline Rush have been jumping off the shelves.

On the Georgia State campus, you can find vending machines selling nothing but energy drinks. These drinks, in their slim 8.3-ounce cans (although many are available in 16-ounce cans), are popular vehicles for caffeine for the younger crowd.

CHRIS ROSENBLOOM FIT TO EAT Have a question of general interest? E-mail Rosenbloom Related: • More on food and drink • Restaurant reviews and search More Rosenbloom [an error occurred while processing this directive] • Chris Rosenbloom, Ph.D., R.D., is a member of the nutrition faculty in the College of Health and Human Sciences at Georgia State University.

Many adults frown upon energy drink consumption while sipping a Starbucks grande coffee, which contains 320 milligrams of caffeine compared to Red Bull's 80 milligrams.

What makes these drinks so popular? Marketing surely helps with claims that they can improve performance in times of high stress (remember final exams?), enhance mental function and provide energy. The energy comes from two sources: calories and caffeine.

While some are available in lower-calorie versions, most contain sugar and about 100 calories in 8 ounces. Caffeine, often coupled with other herbal forms of caffeine such as guarana, mate or kola nut, has long been known to be a stimulant.

One complaint about the energy drink industry is that the caffeine content is not required to appear on the label, so it is hard to know how much of a jolt you will get when you drink one.

Recently, I talked to a college student who complained of insomnia — she didn't drink coffee, tea or caffeinated soft drinks, but she drank three to four energy drinks throughout the afternoon and evening for a total of 600 milligrams of caffeine. That's enough caffeine to keep anyone awake! Energy drinks also contain ingredients such as taurine, carnitine or ginkgo biloba. While none provides caffeine, they might have a mild effect on the brain, helping to sharpen your mental focus. But the research is scant and unclear about their true effects.

Energy drinks in moderation, just like coffee in moderation, are safe for most people. Try to keep caffeine content under 300 milligrams a day.

A newer subset of energy drinks contains those such as Enviga and Celsius, which claim to burn calories or contain "negative calories." Enviga touts research that claims you can burn an extra 100 calories per day when you drink three cans of the product. Enviga contains caffeine (100 milligrams/8 ounces) and EGCG, an extract of green tea. The Center for Science in the Public Interest believes the claims are misleading and has asked the Food and Drug Administration to make Enviga's parent company stop making the energy-burning claims.

Celsius contains about 200 milligrams of a "proprietary" blend of caffeine, guarana and EGCG. While the company has provided research dollars to investigate its claim that the drink will increase resting metabolic rate, none of the studies have been published. It is not surprising to see a rise in metabolism after caffeine consumption; a 3 percent to 4 percent increase in metabolism over a two hours has been reported in scientific literature.

Energy drinks aren't cheap — expect to pay $1.70 to $2 per can. If you think they must taste good because they are so popular, think again. One young college student said they taste like cough syrup. And the sugar-free varieties are cloyingly sweet and leave an artificial sugar aftertaste.