"A small amount can increase concentration and boost athletic performance, but a lot of caffeine decreases concentration and performance," said Hendrickson.
While it varies from person to person, Hendrickson said a safe amount is between 150 and 250 milligrams -- roughly equivalent to an average-sized cup of regular coffee.
"More than 250 milligrams is that amount that studies have shown concentration to go down," he said.
Experts say not much is known about the effects of high doses, such as the amount of caffeine that's in many energy drinks.
"Studies on low doses show there's not a very dangerous effect, but these drinks have much higher doses, and we don't have data yet about what it's doing to our bodies," said Clark.
Because so little is known about these caffeine-loaded drinks and because they're so widely available, medical experts urge caution when consuming them.
"You have to know how your body is going to respond to them, so drink one and see how your body reacts," said Hendrickson.
Even if a person suffers no ill effects from consuming an energy drink, experts advise they should not be consumed regularly or over a long period of time because of all the unknowns.
They also urge people to consume any caffeinated foods and drinks in moderation.
"There is no recommended amount, so the key is to know your body and how caffeine affects it," said Goldberger.
Experts also expressed concern over the growing trend of mixing alcohol and caffeine. This combination can be dangerous, as one recent incident showed.
A group of Central Washington University students became extremely ill after drinking Four Loko, a legal beverage that's a mix of alcohol and caffeine. Another popular drink is a mixture of Red Bull and vodka.
"Some folks think they can drive better by mixing caffeine with alcohol, but no study confirms that," said Clark. "Believing you can go drive this way has all kinds of problems associated with it."
The family of Michael Bedford also has a strong message about the dangers of products like the caffeine powder that led to his death.
"I feel like it should be banned," his grandmother told British media outlets.
"I think there should be a warning on it saying it can kill," his aunt said.