Dietary fat controversy: is it also applicable to children?

Abstract

There is controversy over the use of low-fat, high-carbohydrate diets in the management of hyperlipidemias in adults. Opponents of strict fat restriction focus on the risk of decrease in HDL cholesterol and increase in triacylglycerol concentrations (1). They state that, in contrast, euenergetic substitution of saturated fats by monounsaturated or polyunsaturated fats lowers LDL cholesterol without decreasing HDL cholesterol or raising triacylglycerol. Proponents of fat restriction point to the fact that low fat intakes are usually associated with successful weight loss and maintenance and reduced risk for certain cancers (2). Furthermore, hypertriglyceridemia and the reduction in HDL cholesterol can be avoided by increasing the intake of complex carbohydrates and fiber, instead of simple sugars. The report by Starc et al (3) in this issue of the Journal extends this controversy to the management of childhood hyperlipidemias. In a cross-sectional study of 67 hypercholesterolemic children aged 5.8 ∠ 2.5 y, Starc et al reported that during dietary fat restriction plasma HDL-cholesterol concentrations correlated directly with dietary fat but inversely with dietary carbohydrate intake. An interesting and important contribution of the study was the identification of the relations between specific carbohydrates and HDL cholesterol; although intakes of simple sugars such as glucose and fructose were inversely correlated with HDL-cholesterol concentrations, intakes of complex carbohydrate and fiber were not. These results suggest that limiting the intake of simple sugars, but not necessarily of complex carbohydrates, may prevent the undesirable effects of high-carbohydrate diets. Another important observation of the study by Starc et al was that intake of carbohydrates correlated directly with plasma triacylglycerol but not with LDL-cholesterol concentrations. This suggests that dietary carbohydrates may also raise plasma triacylglycerol concentrations in children. The lack of a relation between LDL cholesterol and dietary fat or carbohydrate is not surprising because LDL-cholesterol concentrations in hyperlipidemic children depend primarily on the severity of the disease and less on diet (4). Furthermore, the blood samples were obtained at a single time point and thus the response to the diet was not known. In an earlier prospective study, Mietus-Snyder et al (5) showed that low fat intakes reduced LDL cholesterol by ♢ 15% in only 19% of hyperlipidemic children, whereas there was a significant reduction in HDL cholesterol in most of the children. The addition of monounsaturated fatty acids to the diet improved the HDL-cholesterol concentrations. These researchers raised the question of whether low fat intake was the right approach, especially because it failed to reduce LDL cholesterol.