Children and people with irregular heartbeats should avoid consuming energy drinks high in caffeine and taurine, such as Red Bull, doctors have warned.

They made their call after carrying out a study which revealed that healthy adults who consumed such drinks recorded significantly increased heart contraction rates 60 minutes later.

"Usually energy drinks contain taurine and caffeine as their main pharmacological ingredients. The amount of caffeine is up to three times higher than in other caffeinated beverages like coffee or cola. There are many side-effects known to be associated with a high intake of caffeine, including rapid heart rate, palpitations, rise in blood pressure and, in the most severe cases, seizures or sudden death," explained Dr Jonas Dörner of the University of Bonn in Germany.

However until now, ‘we haven't known exactly what effect these energy drinks have on the function of the heart', he pointed out.

"There are concerns about the products' potential adverse side-effects on heart function, especially in adolescents and young adults, but there is little or no regulation of energy drink sales," he said.

As part of the ongoing study, Dr Dörner and this team used cardiac MRI (magnetic resonance imaging) to measure the effect of consumption on the function of the hearts of 18 people. All were healthy with an average age of 27.

The participants underwent a cardiac MRI before and one hour after consuming an energy drink that contained 32mg/100ml of caffeine and 400mg/100ml taurine.

The MRIs revealed that one hour after consumption, there was significantly increased contractibility in the left ventricle of the heart. This ventricle receives oxygenated blood from the lungs and pumps it to the aorta, which distributes it throughout the body.

The researchers acknowledged that it was unclear whether these increased contraction rates affected daily activities or athletic performance. However they pointed out that the study did show that consumption of these drinks ‘has a short-term impact on cardiac contractibility'.

"Further studies are needed to evaluate the impact of long-term energy drink consumption and the effect of such drinks on individuals with heart disease," Dr Dörner noted.

He added that while long-term risks remain unknown, children and people with irregular heartbeats, also known as cardiac arrhythmias, should avoid these drinks, as changes in heart contractions could trigger an arrhythmia.

He also called for more research into the risks posed by combining these drinks with alcohol.

Details of these findings were presented at the annual meeting of the Radiological Society of North America (RSNA).