Persistence of Hypertriglyceridemic Effect of Low-Fat High-Carbohydrate Diets in NIDDM Patients

Abstract

Although low-fat high-carbohydrate diets are recommended for patients with non-insulin-dependent diabetes mellitus (NIDDM) in an effort to reduce the risk of coronary artery disease (CAD), the results of short-term studies have shown that these diets can lead to changes in carbohydrate and lipid metabolism associated with an increased risk of CAD. This study has extended these earlier observations by determining the metabolic effects of such diets over a longer period in these patients. The comparison diets contained either 40 or 60% of the total calories as carbohydrates, with reciprocal changes in fat content from 40 to 20% consumed in random order for 6 wk in a crossover experimental design. The ratio of polyunsaturated to saturated fat and the total cholesterol intake were held constant in the two diets. Plasma glucose and insulin concentrations were significantly (P < .001) elevated throughout the day when patients consumed the 60% carbohydrate diet, and 24-h urinary glucose excretion more than doubled (0.8 vs. 1.8 mol/24 h). Fasting plasma total and very-low-density lipoprotein (VLDL) triglyceride (TG) concentrations increased by 30% (P < .001) after 1 wk on the 60% carbohydrate diet, and the magnitude of carbohydrate-induced hypertriglyceridemia persisted unchanged throughout the 6-wk study period. Total plasma cholesterol concentrations were similar after both diets. However, VLDL cholesterol (VLDL-chol) was significantly increased, whereas both low-density lipoprotein (LDL-) and high-density lipoprotein (HDL-) chol concentrations were significantly decreasedafter consumption of the 60% carbohydrate diet. Consequently, neither total-chol-to-HDL-chol nor LDL-chol-to-HDL-chol ratios changed. The results of this study indicate that high-carbohydrate diets lead to several changes in carbohydrate and lipid metabolism in patients with NIDDM that could lead to an increased risk of CAD, and these effects persist for >6 wk. Given these results, it seems reasonable to suggest that the routine recommendation of low-fat high-carbohydrate diets for patients with NIDDM be reconsidered.