The importance of heart and artery disease as a cause of death and disability is difficult to exaggerate: it causes over half of all deaths in the western world and now accounts for one-quarter of deaths in the entire world. This appalling incidence persists in spite of commendable progress in treatment and prevention, particularly in the last two or three decades. Deaths from coronary disease have decreased by a third in the past twenty years and stroke has decreased by a half in the same period. This remarkable improvement, saving thousands of lives per year, has come about due to changes...