Schoolchildren have been showing signs of caffeine addiction after consuming energy drinks such as Red Bull, health campaigners have cautioned.

Bob Tait of Drugs Education UK told a conference of school nurses that caffeine intake — from energy drinks and tablets — is an increasing problem in schools.

Drinks such as Red Bull are cheap and easily available, he said. “Children will drink them on the walk to school, at break and lunch time. If you have got a child who is worked up on an energy drink, they are going to be agitated during lesson time.”

He warned nurses to look out for pupils complaining of chest pains, headaches, restlessness or sleeplessness, Nursing Standard magazine reports.

“If pupils are feeling unwell they are likely to go and see the school nurse. If they come to you with these complaints, be aware that there may be a caffeine problem at the bottom of it.”

Caffeine-rich drinks containing up to 160mg of caffeine per can, and tablets containing 50mg of caffeine per tablet, are said to combat tiredness, improve performance and boost concentration.

Mr Tait’s comments come after a study of 30 university students in Australia found that drinking just one 250ml sugar-free can of Red Bull could increase the “stickiness” of the blood and raise the risk of blood clots forming.

An estimated 330 million litres of energy drinks were consumed in Britain last year, a market worth £1 billion. However Red Bull is banned in countries such as Norway, Uruguay and Denmark because of health fears.

A Red Bull spokesperson denied that the drink, which is distributed to 143 countries worldwide, was dangerous and said that sensitivity to caffeine varies. However, the company does not recommend its product for children, it added.

“Daily consumption of Red Bull should conform to a person’s intake of caffeine and the same is true of children. In general children are more sensitive to caffeine than adults. This is why we do not recommend Red Bull to caffeine-sensitive individuals, including children.”

Cans of Red Bull already carry health warnings advising customers not to drink more two cans a day.

HOW MUCH CAFFEINE IS IN YOUR DRINK

— Cup of tea 47mg

— Cup of instant coffee 65mg

— Cup of filter coffee 95mg

— Starbucks “grande” coffee 330mg

— Can of cola 35mg

— Diet Coke 47mg

— Can of Red Bull 80mg

— Tablet of Pro-Plus: 50mg

— Between 250 and 500mg of caffeine spread over the day is deemed safe. Pregnant women and those sensitive to caffeine are advised to limit their intake of caffeine to less than 300 mg per day, however.

— Some researchers urge caution over other ingredients contained in self-styled energy drinks, including taurine, deltaglucuronolactone and high amounts of sugar.

Source: Times Database, Food Standards Agency