Heart disease is the umbrella term for the diseases of the heart — above all coronary heart disease, in which fatty plaques narrow the coronary arteries, starving the heart muscle of oxygen and causing angina and heart attacks. The term also covers heart failure, arrhythmias, valve disease, and congenital defects. Cardiovascular disease remains the world’s leading killer, and diet sits at the centre of prevention: saturated fat, trans fats, and excess salt raise risk, while fruit, vegetables, whole grains, oily fish, and healthy weights protect. Smoking, inactivity, hypertension, and diabetes complete the risk picture. The good news is that most heart disease is preventable — lifestyle changes rival drugs in power.