The effect of a low-fat, high-carbohydrate diet on serum high density lipoprotein cholesterol and triglyceride.

OBJECTIVE

To determine whether substituting carbohydrate for saturated fat has any adverse effects on serum high density lipoprotein (HDL) cholesterol and triglycerides in free-living individuals.

DESIGN

Randomised crossover trial.

SETTING

General community.

SUBJECTS

Volunteer sample of 38 healthy free-living men with mean (s.d.) age 37 (7) y, moderately elevated serum total cholesterol 5.51 (0.93) mmol/l and body mass index 26.0 (3.6) kg/m2.

INTERVENTIONS

Participants completed two six week experimental periods during which they consumed either a traditional Western diet (36%, 18%, and 43% energy from total, saturated, and carbohydrate, respectively) or a low-saturated fat high-carbohydrate diet (22%, 6% and 59% energy from total, saturated, and carbohydrate, 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.

RESULTS

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 of compliance with experimental diets. Total and low density lipoprotein (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). Fasting triglyceride levels were unchanged throughout the study.

CONCLUSIONS

Replacement of saturated fat with carbohydrate from grains, vegetables, legumes, and fruit reduces total and LDL cholesterol with only a minor effect on HDL cholesterol and triglyceride. It seems that when free living individuals change to a fibre rich high-carbohydrate diet appropriate food choices lead to a modest weight reduction. This may explain why the marked elevation of triglyceride and reduction of HDL cholesterol observed on strictly controlled high-carbohydrate diets may not occur when such diets are followed in practice.