Undeterred by the dizzying variety, the two friends each made a quick choice -- Mountain Dew energy.

Ten-year-old Ian MacLaughlin had, at the recent Toronto Indy, tasted a free sample and liked it.

His friend, Christopher Askin, was also sold. "I just looked at it and said: 'Mountain Dew Energy -- it's good for me. So I just bought it."

The drink the boys chose for their pick-me-up was loaded not only with sugar but with caffeine -- a dose much higher than what is found in their parents' coffee and well beyond the levels Health Canada considers safe for children.

The Mountain Dew Energy label reads: "Contains caffeine. Not recommended for children, pregnant or breastfeeding women, or caffeine sensitive persons."

Ian and Christopher were oblivious to the warning, and so was the store clerk who sold them the drinks.

The bottle of Mountain Dew Energy contains 91 milligrams of caffeine, quite a jolt, but not at all unusual for the new generation of energy drinks.

A can of Red Bull contains 130 mg of caffeine; Full Throttle contains 141 mg; Monster, 169 mg.

"I feel this is totally unacceptable," said Professor Massimo Marcone, a food scientist at the University of Guelph in Guelph, Ont.

"We should really not be marketing caffeine to children and especially in the amounts we are seeing."

He said high levels of caffeine, like those found in energy drinks, cause children to be distracted and unable to concentrate, and interfere with their sleep. Caffeine, the most widely used stimulant in the world, is also habit forming.