Some of the earliest observations on the link between diet and heart disease occured when Dr. Ancel Keys noted a decreased occurence of heart disease and stroke in populations that consumed what he called a Mediterranean Diet. Essentially, this consisted of vegetables, fruit, whole grains, nuts, healthy oils (like olive oil) and fish.
Dr. Keys subsequently noted that healthier diets tended to keep blood cholesterol levels lower and this appeared to be driving the lower rates of heart disease.
Large studies followed that refined our understanding of the link between diet and heart disease. These included the Framingham Heart Study and the Nurses' Health Study, both of which led to a deeper understanding of how diets were related to heart disease.
More recently, however, the INTERHeart study - which compared dietary patterns in 52 countries in relation to the risk of heart disease and stroke - reaffirmed the basic tenets of Dr. Keys early discoveries: No matter where you live, and no matter what your cultural background, consuming a diet that is high in vegetables, fruit and whole grains can lower your risk of heart disease and stroke by as much as 30% in comparison to eating a diet that is high in fat and refined starches.
The biology is now well understood and fairly straightforward. Diets high in vegetables, fruit, whole grains and healthy oils (like vegetable and fish oils) tend to keep LDL, or "bad", cholesterol levels low; they tend to keep blood pressure low; and they tend to interfere with the processes that could lead to blood clots in coronary arteries and in the brain.