84 million American adults (\>1 in 3) have cardiovascular disease, and cardiovascular disease accounts for 1 of every 3 deaths in the United States and has been the number one cause of deaths in every year since 1918. In addition, strokes, heart attacks, and uncontrolled hypertension are sources of significant disability. However, with control of known cardiovascular risk factors (i.e., smoking, body mass index, physical activity, healthy diet, total cholesterol, blood pressure, fasting plasma glucose), the risk of developing cardiovascular disease is markedly reduced. The most uncontrolled risk factor of these seven metrics for cardiovascular health amongst US adults is healthy dietary behaviors. 73 percent of Americans have a poor diet, and \<1 percent have an ideal diet. No other metric of cardiovascular risk comes close - by comparison, the second worst metric is body mass index for which 31 percent have an ideal score, and the remaining five risk factors are all greater than 40 percent with ideal control. The magnitude of the gap that needs closure is greatest with healthy dietary behaviors, yet it frequently receives the least amount of intervention, and the gap has worsened over the past quarter century. Fewer patients with hypertension today are adhering to healthy nutritional habits than patients a quarter century ago. These suboptimal dietary habits are the leading cause of mortality and disability-adjusted life-years lost, greater than smoking, obesity, physical inactivity, high cholesterol, hypertension, or diabetes.

Lifestyle modification is the cornerstone of cardiovascular disease prevention, and healthy nutritional habits are essential to reducing cardiovascular risk. Changes in diet alone are as effective as blood pressure medications, without side effects associated with pharmacologic intervention. Increase nut consumption lowers cholesterol, and reducing sugar-sweetened beverages reduces risk of weight gain.

More recently, greater attention has been brought to the Mediterranean diet. The Mediterranean diet lowers blood pressure, increases HDL cholesterol, and decreases glucose levels. The term "Mediterranean diet" was first coined by Ancel Keys, best known for the Seven Countries Study, which found lower cardiovascular mortality in Mediterranean vs. non-Mediterranean countries. Since Keys' seminal work, multiple observational studies and randomized controlled trials have demonstrated a diet characterized by abundant olive oil and nut consumption and enriched for fruits, vegetables and fatty fish to be the most likely to reduce risk of cardiovascular events, including myocardial infarction, stroke and death. The Mediterranean diet was speculated to have cardiovascular benefit after observational studies suggested benefit, and the evidence solidified after randomized controlled studies showed superiority of the Mediterranean diet in both high-risk primary prevention populations and secondary prevention populations. The PREDIMED study showed a 30 percent reduction in major adverse cardiovascular events, largely through a reduction in stroke, for those patients at high risk for the development of atherosclerotic disease on a Mediterranean diet enriched for olive oil and nut consumption. The Lyon Diet Heart Study enrolled patients after a first myocardial infarction, and those randomized to receiving a Mediterranean diet enriched with more bread, fish, root vegetables and fish had improved survival and fewer myocardial infarctions than those on a usual prudent diet. Neither study demonstrated any adverse effects of the diet. These studies, however, were conducted in Mediterranean countries, and whether this diet can be successfully implemented in a non-Mediterranean population (and whether the benefits would similarly translate) remains to be tested. Observational studies suggest its possibility in a non-Mediterranean population but this finding remains to be confirmed by randomized controlled trial.