According to the study, taking a vitamin D3 supplement on a regular basis may reduce the need for fitting implantable cardioverter defibrillators (ICDs) in certain patients. This is already a costly operation. Heart failure affects 23 million people worldwide and more than half of sufferers are aged 75 or older. Patients with heart failure experience a number of changes in the electrical function of the heart that predispose to potentially lethal cardiac arrhythmias. The vitamin D3 could be found in some natural souces as eggs, dairy products, oily fish (sardines, mackerel), calf’s liver and cod liver oil.