THE EFFECT OF A LOW-FAT, HIGH-CARBOHYDRATE DIET ON SERUM HIGH-DENSITY-LIPOPROTEIN CHOLESTEROL AND TRIGLYCERIDE

Objective: To determine whether substituting carbohydrate for saturate d fat has any adverse effects on serum high density lipoprotein (HDL) cholesterol and triglycerides in free-living individuals. Design: Rand omised crossover trial. Setting: General community. Subjects: Voluntee r sample of 38 healthy free-living men with mean (s.d.) age 37(7)y, mo derately elevated serum total cholesterol 5.51 (0.93) mmol/l and body mass index 26.0 (3.6) kg/m(2). Interventions: Participants completed t wo six week experimental periods during which they consumed either a t raditional Western diet (36%, 18%, and 43% energy from total, saturate d, and carbohydrate, respectively) or a low-saturated fat high-carbohy drate diet (22%, 6% and 59% energy from total, saturated, and carbohyd rate, respectively). Dietary principles were reinforced regularly, but food choices were self-selected during each experimental period. Main outcome measures: Serum lipids, body weight and plasma fatty acids. R esults: Reported energy and nutrient intakes, plasma fatty acids, and a drop in weight from 79.1 (12.5)kg on the Western diet to 77.6 (12.0) kg on the high-carbohydrate diet (P < 0.001) confirmed a high level o f compliance with experimental diets. Total and low density lipoprotei n (LDL) cholesterol fell from 5.52 (1.04) mmol/l and 3.64 (0.88) mmol/ l, respectively on the Western diet to 4.76 (1.10) mmol/l and 2.97 (0. 94) mmol/l on the high-carbohydrate diet (P < 0.001). HDL cholesterol fell from 1.21 (0.27)mmol/l on the Western diet to 1.07 (0.23) mmol/l on the high-carbohydrate diet (P = 0.057), but the LDL:HDL cholesterol ratio improved from 3.17 (1.05) on the Western diet to 2.88 (0.97) on the high-carbohydrate diet (P = 0.004). Pasting triglyceride levels w ere unchanged throughout the study. Conclusions: Replacement of satura ted fat with carbohydrate from grains, vegetables, legumes, and fruit reduces total and LDL cholesterol with only a minor effect on HDL chol esterol and triglyceride. It seems that when free living individuals c hange to a fibre rich high-carbohydrate diet appropriate food choices lead to a modest weight reduction. This may explain why the marked ele vation of triglyceride and reduction of HDL cholesterol observed on st rictly controlled high-carbohydrate diets may not occur when such diet s are followed in practice.