The energy drinks guzzled before cramming for an exam may contain more stimulants than students realize.

The energy drinks' common supplements, taurine and guarana, are used in the drinks as a natural stimulant, said Charles Yesalis, professor emeritus of health and human development.

"[The supplements] are all trying to mimic the adrenaline your body produces," Yesalis said.

In particular, guarana may be deceivingly dangerous, said Edward Krenzelok, director of the Pittsburgh Poison Center at the University of Pittsburgh Medical Center.

"Guarana contains caffeine, so guarana by itself may be misleading," Krenzelok said.

According to the Thomson Micromedex Poisindex database, caffeine comprises three to five percent of guarana. Compared to a traditional eight-ounce cup of coffee that has about 60 milligrams of caffeine, Krenzelok said, some energy drinks have significantly more caffeine.

"Most people can tolerate up to 200 milligrams of caffeine without a problem if consumed throughout the day," said Dr. Douglas Aukerman, assistant professor in the department of orthopedics and rehabilitation and sports medicine.

On the other hand, Krenzelok said, taurine should not present any type of health problem since it is an amino acid -- a compound that is naturally present in the body and is known as the body's building block.

Aukerman warns that it could be dangerous to mix energy drinks with alcohol or to drink them before exercising.

"Sometimes [energy drinks] can mask how intoxicated or inebriated you really are," Aukerman said. "Because they're a diuretic, if you take them before exercise or in large amounts they can dehydrate you by making you lose more body fluids."

There are some signs to look out for to indicate that students may be experience the negative effects of energy drinks, Yesalis said. Increased blood pressure and pulse rate, jitteriness and uneasiness can all suggest an overuse of the products, Yesalis said.

"If your heart's beating like a trip hammer, and you can't get to sleep, you've probably had too much," Yesalis said.

Yesalis said when choosing an energy drink, he recommends avoiding ones that have anything that is banned by the FDA, such as ephedra compounds.

FDA Public Affairs Specialist Michael Herndon said the supplements used in energy drinks are considered dietary supplements as opposed to conventional food, and the FDA only deals with supplements when there is an issue of someone getting sick from using them.

"If energy drinks are not labeled as supplements, they are regulated as a conventional food as you would see an apple or an orange or anything else you'd see in a grocery store," Herndon said.

Thomas Gallagher (junior-premedicine) said he doesn't worry about consuming energy drinks when he studies. He added that Red Bull cans advertise that the drink helps with attention. But he said he isn't particularly partial to drinking energy drinks just to get a caffeine boost.

"If anything, I'd prefer coffee," Gallagher said. "I like how it tastes better than Red Bull and stuff like that."

Although he believes that energy drinks can be safe if used in moderation, Yesalis said students shouldn't overdo it.

Just as people should use common sense while consuming alcohol, the same should be done when using energy drinks, he added.

Students may still experience similar withdrawal symptoms as they would when missing their habitual morning cup of coffee, Yesalis said.

"As a dad, I'd rather see you guys get a little more sleep where you wouldn't need that [energy drink]," Yesalis said.