Objective: To evaluate the effect of diet and drug intervention separately and combined in the treatment of primary hypercholesterolemia.
Design: The study was conducted as a randomized, placebo-controlled factorial trial, double-blinded for drug intervention.
Setting: Subjects were recruited from a population-based cholesterol screening programme.
Subjects: 215 middle-aged men with primary hypercholesterolemia, free from cardiovascular disease.
Interventions: Subjects were randomized to one of four intervention groups: (1) placebo and US National Cholesterol Education Program step 1 diet; (2) placebo and step 2 diet; (3) pravastatin 20 mg day-1 and step 1 diet; or (4) pravastatin 20 mg day-1 and step 2 diet. The intervention period was 6 months.
Main outcome measurements: Efficacy measurements included: serum total cholesterol, HDL cholesterol, triglycerides, apolipoproteins A1 and B. LDL cholesterol was calculated. For safety, values of ALAT, ASAT and CK were measured.
Results: In the group receiving the step 1 diet only, lipid values were stable during the study period. In the placebo group on the step 2 diet, total cholesterol decreased by 6.3% (0.47 mmol L-1 (95% CI: 0.28, 0.67)) during 6 months. In the group receiving both pravastatin and the step 1 diet, there was a mean reduction in serum total cholesterol of 19.4% (1.46 mmol L-1 (95% CI: 1.20, 1.72)). In the group treated with pravastatin and the step 2 diet, the 6 months of data show a reduction of 20.7% (1.55 mmol L-1 (95% CI: 1.30, 1.80)).
Conclusions: If drug therapy with a HMG-CoA reductase inhibitor is considered necessary, a step 2 diet has no additional lipid-lowering effect compared with a step 1 diet in men with primary hypercholesterolaemia. However, favourable 'side-effects' of a lipid-lowering diet, such as weight loss and lowering of blood pressure, may still warrant a low-fat diet in these cases.