Introduction The concept that diet, serum cholesterol and cardiovascular disease are causally related and  gave rise to the diet-heart hypothesis nearly 70 years ago. This hypothesis postulates that reducing dietary saturated fat reduces serum cholesterol, thereby reducing the risk of cardiovascular disease. Today, this concept has been transformed from a hypothesis into public health policy as current guidelines recommend reducing the intake of dietary saturated fat.1 Not all practitioners agree, however, and a reappraisal of the evidence may help resolve this controversy. An abbreviated history Dr  Ancel Keys first proposed the diet-heart hypothesis in the 1950s. Several years later, he published the Seven Countries Study that reported a strong correlation between dietary fat and coronary mortality in seven countries.2 His hypothesis rapidly gained support and by 1977 the US Senate Select Committee on Nutrition and Human Needs formally recommended that Americans should reduce their consumption of total and saturated fat.3 Many scientists disagreed and a vitriolic debate soon followed.4 Presently, the American Heart Association recommends ‘lowering intake of saturated fat and replacing it with unsaturated fats, especially polyunsaturated fats’ to reduce cardiovascular disease.