In recent years, controversy has also swirled around energy drinks, which also contain caffeine.

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Most of the stimulating supplements are derived from the herbal plant ma huang, and often also contain caffeine derived from guarana.

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Although some coffees may contain more caffeine than Monster's energy drinks, Herrera says that coffee is typically served hot and consumed more slowly than energy drinks.

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The American Academy of Pediatrics has warned against kids consuming energy drinks, for the high levels of caffeine they can contain.

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The company said its energy drinks contain about 10 milligrams of caffeine an ounce, less than half the concentration of leading coffee-house brews.

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In Chicago, Alderman Edward Burke introduced legislation earlier this year that would ban the sale of energy drinks that contain more than 180 milligrams of caffeine per container and include taurine or guarana.

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Caffeinated energy drinks can contain anywhere from 160 to 500 mg of caffeine, according to the FDA. For most people caffeine is not a problem, though it can lead to jitteriness and other mildly unpleasant effects.

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The AAP has advised pediatricians to recommend to their patients not to use these products and energy drinks, since they contain potentially high amounts of stimulants such as DMAA and caffeine, which can elevate the possibility for developing dehydration, palpitations or dangerous arrhythmias, or insomnia.

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