Youngsters who mix alcohol with energy drinks risk heart palpitations and disturbed sleep, researchers warn.

A study found that the highly-caffeinated drinks used by millions to make them extra-alert on a night out raised the odds of a range of health problems.

Revellers who used energy drinks as a mixer were six times as likely to suffer heart palpitations as those who drank their alcohol straight or with a normal soft drink.

They also had four times the odds of sleep difficulties and were more prone to tremors, irritability and so-called jolt and crash episodes – sudden, short-lived bursts of energy followed by exhaustion.

The symptoms are similar to those produced by caffeine, one of the chief ingredients of energy drinks such as Red Bull.

One can of Red Bull contains 80mg of caffeine, around the same as two cans of cola and slightly less than a mug of instant coffee.

Andrea Carr, of the University of Tasmania, said that to avoid side-effects, ‘consumers of energy drinks alone or combined with alcohol should be aware of the caffeine content of their drinks and any additional caffeine they may have consumed that will contribute to an exacerbation of these effects’.

Contrary to previous belief, the study of 403 men and women aged between 18 and 35, reported in the journal Alcoholism: Clinical & Experimental Research, found energy drink fans were less likely to take risks when drinking.

A spokesman from the British Soft Drinks Association said: ‘People who choose to drink alcoholic drinks should consume them in moderation, whether they are mixed with energy drinks or not.’

Subjects in the study were also surveyed about their physical and mental health and how often they took risks or lost control by, for example, drunk driving or getting into fights.

The results revealed that energy drinks may cancel out some of alcohol’s sedating effects, leaving drinkers more awake and less likely to suffer signs of tipsiness such as slurred speech or clumsiness.
But this alertness came at a cost.

Researcher Amy Peacock said: ‘They also had a greater chance of experiencing several side-effects linked to over-stimulation, including heart palpitations, increased speech speed, sleeping difficulties, agitation and tremors, jolt and crash episodes, irritability and tension.’

Some researchers have said that energy drinks’ masking of drunkenness could badly impair judgement, leading people to do things they might not do otherwise – such as drinking and driving or getting into fights.

This study found the opposite to be true, with energy drink fans being less likely to take a range of risks.

But the researchers, who report their findings in the journal Alcoholism: Clinical & Experimental Research (MUST CREDIT), said the topic needs to be studied more deeply and said that energy drink lovers shouldn’t assume that being extra alert somehow protects them from danger.

Previous research has linked energy drinks with heart problems, with just one can raising blood pressure and making blood more ‘sticky’- and so potentially raising the odds of heart attacks and strokes.