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We compared a high-carbohydrate diet with a high-fat diet (specifically, a diet high in monounsaturated fatty acids) for effects on glycemic control and plasma lipoproteins in 10 patients with non-insulin-dependent diabetes mellitus (NIDDM) receiving insulin therapy. The patients were randomly assigned to receive first one diet and then the other, each for 28 days, in a metabolic ward. In the high-carbohydrate diet, 25 percent of the energy was in the form of fat and 60 percent in the form of carbohydrates (47 percent of the total energy was in the form of complex carbohydrates); the high-monounsaturated-fat diet was 50 percent fat (33 percent of the total energy in the form of monounsaturated fatty acids) and 35 percent carbohydrates. The two diets had the same amounts of simple carbohydrates and fiber. As compared with the high-carbohydrate diet, the high-monounsaturated-fat diet resulted in lower mean plasma glucose levels and reduced insulin requirements, lower levels of plasma triglycerides and very-low-density lipoprotein cholesterol (lower by 25 and 35 percent, respectively; P less than 0.01), and higher levels of high-density lipoprotein (HDL) cholesterol (higher by 13 percent; P less than 0.005). Levels of total cholesterol and low-density lipoprotein (LDL) cholesterol did not differ significantly in patients on the two diets. These preliminary results suggest that partial replacement of complex carbohydrates with monounsaturated fatty acids in the diets of patients with NIDDM does not increase the level of LDL cholesterol and may improve glycemic control and the levels of plasma triglycerides and HDL cholesterol.

We studied the metabolic effects of stearic acid (18:0) on plasma lipoprotein levels in 11 subjects during three dietary periods of three weeks each. The three liquid-formula diets, which were used in random order, were high in palmitic acid (16:0), stearic acid, and oleic acid (18:1), respectively. Caloric intakes were the same during the three periods. As compared with the values observed when the subjects were on the high-palmitic-acid diet, plasma total cholesterol decreased by an average of 14 percent during consumption of the high-stearic-acid diet (P less than 0.005) and by 10 percent during consumption of the high-oleic-acid diet (P less than 0.02). Low-density lipoprotein cholesterol levels fell by 21 percent in subjects on the high-stearic-acid diet (P less than 0.005) and by 15 percent in subjects on the high-oleic-acid diet (P less than 0.005). No significant differences were observed in the plasma levels of triglycerides or high-density lipoprotein cholesterol among the three diets. Measurements of the intestinal absorption of palmitic, stearic, and oleic acids revealed essentially complete absorption of each during the three dietary periods. The oleic acid content of plasma triglycerides and cholesteryl esters increased significantly during the high-stearic-acid period, suggesting that stearic acid is rapidly converted to oleic acid. We conclude that stearic acid appears to be as effective as oleic acid in lowering plasma cholesterol levels when either replaces palmitic acid in the diet.