Cardiovascular epidemiology and the rise of the heart-healthy diet

Today, a direct relationship between dietary intake and an individual's risk of coronary artery disease is considered a foregone conclusion by many. But fifty years ago, this was not the case. In the years following World War II, a multidisciplinary array of biomedical professionals formed the new field of cardiovascular epidemiology, seeking to clarify the biological and societal factors underlying coronary artery disease. During the 1950s and 1960s, this first generation of cardiovascular epidemiologists continually debated the exact nature of the relationship among cholesterol, diet, and cardiovascular risk. In this paper, I examine the history of these debates regarding the diet-heart hypothesis, which proposed that diet was causally linked to coronary artery disease, and demonstrate how these debates influenced the introduction of the heart-healthy diet. The diet-heart hypothesis would become one of the conceptual centerpieces of cardiovascular epidemiology as well as a central focus of methodological debate. Almost immediately, the new field was mired in contentious debate as investigators struggled to determine exactly what role, if any, diet played in coronary artery disease. Researchers devised cross-sectional and longitudinal studies of coronary artery disease and developed dietary regimens for the prevention and management of coronary artery disease. These dietary regimens constituted the introduction of the heart-healthy diet. From the mid-1950s onward, investigators reappropriated low-fat dietary regimens once promoted for weight loss into heart-healthy diets and the American public became vigorous consumers of heart health cookbooks and advice books. The formative years of cardiovascular epidemiology and the simultaneous introduction of heart health literature offer important lessons about the creation and adoption of new public health knowledge. The debates created a profound professional rift among the first generation of cardiovascular epidemiologists as they debated whether epidemiological analyses could and should inform therapeutic practices. If dietary intake and coronary risk profiles were correlated statistically, could this be extrapolated to a causal relationship? And if so, how could this information be deployed in the service of individual patients? Finally, this paper examines how and why the American public was quick to accept the tenets of heart healthiness even while cardiovascular epidemiologists, physicians, and public health officials debated the merits of the diet-heart hypothesis.