Effects of Dietary Carbohydrate and Fat Intake on Glucose and Lipoprotein Metabolism in Individuals With Diabetes Mellitus

The dietary treatment of individuals with diabetes remains a controversial issue. The major emphasis in recent years has been on the reduction of total fat and saturated fat and replacement with complex carbohydrate. The rationale for this approach is based on the premise that such diets will reduce the risk of coronary artery disease (CAD) by reducing total and low-density lipoprotein cholesterol concentrations. In this article, we review the available data and conclude that there is little evidence to support the notion that low-fat high-carbohydrate diets per se lead to any reduction in the risk for CAD in individuals with diabetes. The only data indicating that low-fat high-carbohydrate diets lead to beneficial effects on carbohydrate and lipoprotein metabolism are confounded either by the lack of suitable experimental control, by the fact that diets also differed in the type of dietary fat and amount of dietary cholesterol, or were enormously enriched in dietary fiber. When these factors are taken into consideration, there appears to be little evidence in support of the view that substituting carbohydrate for fat in the diets of individuals with diabetes results in any measurable beneficial effect. Indeed, it could be argued that the most characteristic defects in carbohydrate and lipoprotein metabolism are exacerbated in response to low-fat high-carbohydrate diets. Alternatively, the data presented herein strongly suggest that diets containing conventional quantities of fat, in which saturated fat is replaced by unsaturated fat and dietary cholesterol reduced, would result in the desired reductions to total and low-density lipoprotein cholesterol concentrations without the adverse effects of increased postprandial glucose and insulin concentrations, increased fasting and postprandial total and very-low-density lipoprotein triglyceride concentrations, and decreased fasting high-density lipoprotein cholesterol concentrations.