Dietary treatment of hyperlipidemia

In the debate that follows, two leading experts present differing viewpoints on the dietary treatment of hyperlipidemia. Dean Ornish reviews the modest reductions in total- and low-density-lipoprotein (LDL)-cholesterol levels obtained in clinical trials in persons instructed to follow diets similar to the Step I and II Diets recommended by the American Heart Association (AHA) and the US National Cholesterol Education Program (NCEP), which restrict fat intake to 30% or less of calories and dietary cholesterol intake to 200–300 mg/day. In comparison, Dr Ornish cites the results of the more aggressive dietary changes prescribed in the Lifestyle Heart Trial (10% of calories as fat, cholesterol intake 5 mg/day or less), which led to a 24% decrease in total-cholesterol and a 37% decrease in LDL-cholesterol levels, as well as regression of cardiovascular disease. In defense of the NCEP guidelines, Margo Denke cites two recent trials, the St Thomas' Atherosclerosis Regression Study (STARS) and the Lyon Diet Heart Study, in which diets similar to the Step II Diet were sufficient to stop the progression of atherosclerosis and decrease the rate of cardiovascular events. Dr Denke also points out that the results of the Lifestyle Heart Trial may have been confounded by substantial weight loss, which can in itself affect triglyceride and high-density-lipoprotein (HDL)-cholesterol levels, blood pressure, and glucose metabolism. Conversely, restriction of dietary fat intake to less than 25% of calories increases triglyceride and lowers HDL-cholesterol levels. Both experts agree that dietary therapy is central to the prevention and treatment of coronary heart disease. However, their differences indicate that we still do not have agreement on the nutrient composition of the optimal therapeutic diet, nor is there consensus on the means of initiating or sustaining the required changes in lifestyle. Clearly, future clinical trials that study the progression of coronary heart disease should be designed to address these issues.