Energy drinks packed with caffeine can change the way the heart beats, researchers warn. The team from the University of Bonn in Germany imaged the hearts of 17 people an hour after they had an energy drink. The study showed contractions were more forceful after the drink. The team told the annual meeting of the Radiological Society of North America that children and people with some health conditions should avoid the drinks. They showed the chamber of the heart that pumps blood around the body, the left ventricle, was contracting harder an hour after the energy drink was taken than at the start of the study. Dr Dorner added: “We’ve shown that energy drink consumption has a short-term impact on cardiac contractility. “We don’t know exactly how or if this greater contractility of the heart impacts daily activities or athletic performance.” The impact on people with heart disease is also unknown. However, the research team advises that children and people with an irregular heartbeat should avoid the drinks.