Dietary determinants of plasma cholesterol change in the recruitment phase of the Lipid Research Clinics Coronary Primary Prevention Trial.

We have investigated the relationship of diet to plasma lipid and lipoprotein levels in 6494 hypercholesterolemic (Type IIA) men who were instructed in an isocaloric, 400 mg cholesterol, 0.8 polyunsaturated-to-saturated fat ratio diet in the course of recruitment for the Lipid Research Clinics Coronary Primary Prevention Trial. Single 24-hour dietary recalls, plasma total and high density lipoprotein cholesterol, and total triglyceride determinations were obtained approximately 1 month before and 1 month after dietary instruction. Cross-sectional correlation analysis disclosed no significant association between diet and plasma cholesterol at entry. However, when diet-associated changes were similarly analyzed, weight loss, decreased intakes of saturated fat and cholesterol, and increased intake of polyunsaturated fat were all significantly and independently predictive of falls in plasma cholesterol, mainly in its low density lipoprotein fraction. The multiple correlation coefficient for the resultant four-variable regression model was 0.29. Diet-associated changes in plasma very low density lipoprotein cholesterol were less marked but in the same direction. These dietary changes were also weakly associated with a lowering of plasma high density lipoprotein cholesterol, while weight loss had an opposite effect of similar strength. When one takes into account the variability of dietary recall data, the observed diet-associated changes in plasma cholesterol were compatible with the findings of metabolic ward studies.