London: It is just caffeine that delivers the kick in energy drinks, rather than addition of much vaunted ingredients such as guarana or taurine, says a new research.

The study found that there is an "overwhelming lack of evidence to substantiate claims that these ingredients (taurine, guarana and ginseng), boost performance."

Energy drinks also contain ginseng, glucuronolactone, vitamin-B and other compounds.

Researchers sifted dozens of articles that examined the effects of energy ingredients alone and/or in combination with caffeine, the Nutrition Reviews journal reported.

With the exception of some weak evidence for glucose and guarana extract, there was little evidence substantiating claims that components of energy drinks, other than caffeine, contribute to the enhancement of physical or cognitive performance, according to the Daily Mail.

A previous study found that energy drinks have up to 14 times more caffeine than other soft drinks.

Besides, doctors warned that children given energy drinks could pile on the pounds because they are not active enough to burn off the extra calories.

Research published earlier this year warned children should never be given energy drinks, only fruit juice, milk and water.

They said energy drinks - which contain between 10 and 270 calories a serving - should never be given to children.

A hidden problem with energy drinks is caffeine, which can reach toxic levels up to 14 times greater than in other soft drinks.

The stimulant has been linked to seizures, diabetes, heart problems and behavioural disorders.