The energy drink market is one of the fastest growing in the beverage industry and shows no sign of losing its wings.

Energy drinks have become the newest fuel for a caffeine-crazed society, and that makes some medical experts nervous.

People are downing them casually and indiscriminately as a power smack in a can - drinkers will chug one before a workout, mix in liquor for a stiff energy cocktail and crack them open for all-nighters.

But what is behind the buzz?

An affliction for addiction

A late night behind her, an exam later in the day and homework deadlines pressing, Erika Huerta sought the refuge of a green Monster Energy to get her going for her early-morning library crunch session.

The medical technology senior downs the energy drink daily, usually one in the morning and maybe a couple more at night if she needs a boost while studying.

"I have built up a tolerance," Huerta said. "But I also think I'm somewhat addicted to it because if I don't have an energy drink in the morning - I'm not fully awake. I don't feel like doing anything."

Stimulants found in energy drinks can lead to an addiction, said Scott Sehnert, an MSU sports and cardiovascular nutritionist.

"(Caffeine) is a drug - it is addictive," said Sehnert, who works in the MSU Department of Radiology. "So when you get yourself used to drinking one to be enough, you'd then have to drink two, and next it would be three. You get in this addictive situation, which is not going to be good overall."

Huerta's high demand for energy lends to an understanding of why the products are so successful.

Booming business

Beverage companies are adapting their product lines to meet the evolving needs of a more open-minded customer base.

Gary Hemphill, managing director of Beverage Marketing Corp., said the market's success is because of its ability to tap a very specific consumer need - energy.

"People used to drink based on thirst alone," Hemphill said. "But the market has changed, and people are open to drinking beverages for a wide range of reasons."

He said energy drinks are a bona fide category, not a fad.

In 2006, 240 million gallons of energy drinks were purchased - a 50 percent volume increase from the previous year, Hemphill said.

More than 3 billion cans of Red Bull Energy Drink were consumed worldwide last year, according to Red Bull's sales figures.

Hemphill said the category has experienced strong double-digit growth since its introduction into the U.S.

"It's going to have healthy growth for at least the foreseeable future," he said. "We expect it to grow annually at least 20 percent for the next five years."

What began with the Austrian-brewed Red Bull has grown into a sprawling market with hundreds of beverage companies fighting for elbow room.

While Red Bull maintains the lead, Monster Energy, Rockstar Energy Drink and Coca-Cola are among the many competitors trying to garner the attention of consumers.

Coke's energy staple Full Throttle is now available as a Slurpee, and Monster recently unveiled a line of three Java coffee energy drinks.

Many of the new players have added new ingredients, more caffeine and bigger cans - all in the spirit of one-upmanship.

Iffy ingredients

If you can't say it, don't drink it.

That's Sehnert's epigrammatic advice when it comes to the psychobabble of energy drink ingredients such as taurine, guarana, inositol and glucuronolactone.

Taurine is an amino acid the body produces naturally, and also can be obtained from eating certain meat and fish.

Guarana seed extract is essentially a form of caffeine.

Glucuronolactone is an end product of glucose metabolism, Sehnert said.

"I don't know how in the world that's going to benefit you," he said.

The same holds true for most of these substances. Little is known about their positive and negative effects on the human mind and body, he said.

Red Bull claims to "improve performance, increase concentration and improve reaction speed, stimulate the metabolism and increase endurance," according to an e-mail from Patrice Radden, a spokeswoman for the company.

"Numerous scientific studies in the fields of sports medicine, internal medicine and psychology confirm the claims made for Red Bull," she wrote.

There are a lot of reasons to be concerned with the various blends of herbs and stimulants, Sehnert said.

Since energy drinks are classified by manufacturers as dietary supplements, they fall outside the need for legal approval by the Food and Drug Administration.

"What makes me nervous about a lot of these different energy drinks is they have these different blends, so you can get six, seven or eight different types of stimulants, and now you've really put a stress on your heart and vasculature," Sehnert said.

Sehnert commended Red Bull for having its product tested by NSF International, a self-proclaimed public health and safety company.

The nonprofit, nongovernment agency certifies all ingredients on the label are correctly identified and quantified, and do not contain any unacceptable quantities of unwanted contaminants.

But Sehnert said Red Bull also is the sole NSF-certified energy drink, leaving many questions about the contents of the hundreds of other brands.

"You could have a boatload of other stimulants in there and not know it," he said. "You don't know the true number of milligrams of caffeine either. When it comes to ginseng and ginko biloba ? you don't know the purity or quality."

Concocting various herbs together can have dangerous results - including heart arrhythmias, increased heart rate and high blood pressure, Sehnert said.

"Some herbs have been tested extensively but some haven't," he said. "There's just a greater risk of those things occurring, whether it's damaging your liver or risking heart problems."

A lengthy label should set off red flags in the consumer's head - the longer the list of ingredients, the more potential there is for a negative effect on the body, Sehnert said.

"The combination of the things they're putting in there maybe by themselves won't harm you, but when you combine them they potentially could," Sehnert said.

Of the lists of common ingredients among energy drinks, caffeine is the only one that has been thoroughly tested.

There are a number of known benefits to caffeine, such as the ability for increased alertness and concentration, but such benefits can vary from person to person.

Sehnert warns energy drinks could result in hyperactivity and stunted brain growth for adolescents and young teens. The elderly and people on medication also may be adversely affected.

Bombs at the bar

The growing popularity of mixing energy drinks and liquor has made it trickier for bartenders to identify when someone needs to be cut off.

People consuming energy drinks will show the same signs as someone who hasn't drank a lot, has a higher tolerance or is able to better handle their liquor than others, said Kim Drago, manager at P.T. O'Malley's, 210 Abbott Road.

"There's not really a way I can identify a person as being highly intoxicated. But (people who drink energy drinks) seem OK because they have a heightened sense of awareness from drinking Red Bull," she said. "There's a lot of people in the college atmosphere. People do drugs, too. That may affect their awareness or the way (they) act."

The depressive nature of alcohol combined with the brain stimulation of energy drinks can create a nightmarish situation, Sehnert said.

"Someone can just continually drink Red Bull and vodka and because they're not getting this tired feeling … they'll continue to drink more," he said.

The result can be a greater risk of having alcohol toxicity or, because the drunken grogginess never takes hold, they might pick up the car keys, Sehnert said.

"That could be a really scary situation," he said.

While Red Bull can be found in many bars, Radden said the company is not marketing it as anything more than a nonalcoholic energy drink.

Some beverage companies have caught on to the popularity of energy-infused alcoholic mixers - creating caffeinated malt beverages that are packaged very similarly to normal energy drinks.

In 2002, Miller Brewing Co. introduced its alcoholic energy drink Sparks. The can is silver with an orange band at the top.

The ambiguous design has made it virtually unknown to some local law enforcement until recently.

On Welcome Weekend last year, East Lansing police Detective James Campbell had his first encounter with Sparks.

He saw two people walking on East Lansing side streets from party to party while drinking the beverage, he said. They showed all the same signs of intoxication as someone drinking regular alcohol, Campbell added.

"The can looks like an energy drink, and that's all they were drinking that night," he said. "I took the can, put it to my nose, smelled the can and all this stuff trying to figure out what exactly it was - and they told me it was just an energy drink."

However, East Lansing police Chief Tom Wibert said it usually does not take officers long to notice new products like Sparks.

"Most of the time, just because of the marketing, we're going to know what people are drinking," he said. "If a new beverage is introduced to the general population, it doesn't take too long before our officers are seeing it out on the street. There might be a little lag time … but certainly wouldn't be that long."

Energy in the end

After all is said and done, Sehnert said moderation is the key.

"Simple energy drinks, like Red Bull, in moderation - it's not going to be harmful," he said. "Nor do I think it's necessarily going to be healthful. In moderation, within specific populations, you're all right."

Before cracking one open, people may want to think about other alternatives for energy, he said.

"I'll also prefer coffee over an energy drink because caffeine in coffee is coming from a plant, so you're actually getting some antioxidants from drinking it," Sehnert said. "I'm not trying to tell everybody to go get some Starbucks, but in relation to energy drinks, if you need to stay up another hour to study I don't have a big problem with drinking one."

Jon Schultz can be reached at schul320@msu.edu.