In the last decade, our understanding of the nutrients and foods most likely to promote cardiac health has improved substantially, owing in part to the data from several large and carefully conducted prospective cohort studies, including the Nurses' Health Study (NHS) and Health Professionals' Follow-up Study (HPFS). Using more refined dietary assessment tools and multiple measurements, the NHS and HPFS have provided a wealth of information not only on major types of fat and different classes of fatty acids, but also other aspects of diet, including antioxidants, folate, fiber, dietary glycemic load, and overall dietary patterns. These studies, along with metabolic, clinical and other epidemiological studies, have provided strong evidence for a major role of dietary modification in the prevention of coronary heart disease (CHD).