Determinants of plasma cholesterol responsiveness to diet.

Plasma cholesterol change, or 'responsiveness', to dietary saturated fat modification has long been acknowledged. The present study sought to determine the specific, predicted response of each cholesterol subfraction to known dietary manipulations. Two metabolically controlled diets, one with a low polyunsaturated:saturated fat (low P:S) ratio, and one with a high P:S ratio were fed in a crossover design to sixty-seven normolipidaemic subjects pooled from six foregoing metabolic studies. A series of statistical analyses was performed to identify the lipids and subfractions independently affected by the diet crossover. Multivariate analysis of variance revealed that the changes in total cholesterol (delta TC), low-density-lipoprotein-cholesterol (delta LDL-C), and high-density-lipoprotein-cholesterol (delta HDL-C) were the only statistically significant diet-specific 'responsive' lipids. Multiple regression was performed to identify the independent predictors of delta TC, delta LDL-C and delta HDL-C. It was found that age (years), extent of change in dietary saturated fat, and baseline LDL-C (mg/l) levels determine LDL-C change, while extent of change in saturated and polyunsaturated fat, and baseline HDL-C (mg/l) levels can predict HDL-C change. A series of equations to predict lipoprotein responsiveness to diet are derived for potential use in clinical practice.