Nutrition in Clinical Medicine: Evolving Knowledge in Nutrition

Just as new medications often have advantages over previous ones, diet approaches evolve as well, with new dietary methods building on previous ones and research studies putting diets to the test. Heart–healthy diets are a case in point. For decades, cardiologists have encouraged heart patients to switch from red meat to white meat, trim away chicken skin, and stay physically active. These steps were modestly helpful. Following such guidance, an average patient experienced roughly a 5 percent drop in low density lipoprotein (LDL or “bad”) cholesterol.²

However, in 1990, a Harvard–trained physician named Dean Ornish published the results of a study using a much more vigorous regimen.³ His research participants had significant heart disease. His experimental treatment included a low–fat, vegetarian diet, smoking cessation, modest exercise, and stress management. The diet was logical: Foods from plants have no cholesterol and no animal fat, so a vegetarian diet ought to have a major effect on cholesterol levels. For comparison, his study included a control group that received the usual care that doctors provide for heart patients.

The results made medical history. Not only did the program reduce cholesterol far more effectively than previous diets; it visibly changed the disease process itself. Angiograms done before and after the one–year intervention showed that participants in the control group gradually worsened. But the patients in the experimental group had a very different experience. Their coronary arteries were beginning to open up again, so much so that signs of reversal were clearly evident in 82 percent of participants within the first year.

In 1999, Dr. Caldwell Esselstyn, a Cleveland Clinic surgeon, published the results of a remarkable 12–year study integrating nutrition with medications.⁴ In a group of patients with severe heart disease, he used a low–fat, vegan diet, similar to that used by Dr. Ornish. For any patient whose total cholesterol remained above 150 mg/dl despite the diet, he added cholesterol–lowering medications. In the ensuing 12 years, the research participants had no cardiac events. The combination of the diet and judiciously used medications made the patients practically heart–attack–proof. 

Then, in 2005, David Jenkins, from the University of Toronto, took things a step further. Starting with a vegetarian diet, he emphasized foods with known cholesterol–lowering properties–oats, soy, and certain nuts, for example. In four weeks’ time, LDL cholesterol fell nearly 30 percent.⁵ As research has moved forward, our idea of an effective diet has advanced as well.

The same sort of trend has occurred in the approach to cancer. For many years, lifestyle advice from cancer authorities was limited to avoiding tobacco and getting regular checkups. But it has become clear that diet plays a major role in cancer risk. We now encourage all patients to include more fruits and vegetables in their routines, to focus on foods that are rich in antioxidants, and to limit fat and boost fiber.

More recently, nutritional steps have been tested not only for cancer prevention, but for cancer survival. Studies of individuals diagnosed with breast or prostate cancer have shown that diet makes a major difference in the ensuing years.