Experts worry about caffeine levels in energy drinks

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A drink containing more than twice as much caffeine as the average flat white is the latest weapon in the energy drinks war.

New Zealand company Demon is launching the product next week, with director Andy Smith predicting the market could turn over as much as $1 billion a year.

Energy drink manufacturers have already supersized cans and raised caffeine contents to their legal limit in a bid to maintain their share of a crowded market.

But the moves have raised concern among teachers and dieticians about the effects of such drinks on children.

The 60ml Demon Energy Shots contain 200mg of caffeine and are being marketed as "dietary supplements". The average flat white contains 80-100mg.

While Smith stressed the shots complied with the Australia New Zealand Food Standards Code, school staff reported student concentration levels dropping once energy drinks wore off.

Malcolm Milner, principal of Balmoral Primary in Auckland, said he had concerns about brain development and how caffeine affected the brain and body.

Dietician Kath Fouhy said energy drinks had a peak and trough effect on kids.

"Caffeine improves concentration but when it's coupled with all that sugar you get a big energy spike and then you come down off the energy spike you get a big trough," she said.

"When kids are in that trough they don't have very good concentration levels and they get tired and irritable."

Most energy drinks are classed as "formulated caffeinated beverages" and limited to 320mg of caffeine a litre by the New Zealand Food Standards.

Labels must carry the maximum daily consumption level and a warning that children, and pregnant and lactating women should not drink it. Most brands contain the maximum amount of caffeine legally permitted, sugar and guarana - a plant product with about twice the caffeine of coffee beans.

Food Standards Australia New Zealand spokeswoman Lydia Buchtmann said there was no need to lower caffeine limits in energy drinks or to regulate the guarana content.

"When pure caffeine is added as a food additive you have to limit that level."