Thematic review series: patient-oriented research. Dietary fat, carbohydrate, and protein: effects on plasma lipoprotein patterns

In general, under isoweight conditions, different types of dietary protein or individual amino acids have little effect on lipoprotein patterns. Dietary carbohydrate tends to increase plasma triglyceride when it displaces fat, accompanied by a decrease in HDL cholesterol concentrations. Potential differential effects of types of carbohydrate are difficult to assess because of differences in rates of absorption and confounding of dietary fiber. Saturated fatty acids increase LDL and HDL cholesterol, whereas trans fatty acids increase LDL but not HDL cholesterol. Unsaturated fatty acids decrease LDL and HDL cholesterol, polyunsaturated more so than monounsaturated. There has been considerable interest in the potential benefit of major shifts in dietary macronutrients on weight loss and lipoprotein patterns. Short-term data favor substituting protein and fat for carbohydrate, whereas long-term data have failed to show a benefit for weight loss. During an active weight loss period low-carbohydrate diets more favorably affect triglyceride and HDL and less favorably affect LDL cholesterol concentrations. Additional efforts need to be focused on gaining a better understanding of the effect of dietary macronutrient profiles on established and emerging cardiovascular disease risk factors, mechanisms for changes observed and contributors to individual variability. Such data are needed to allow reassessment and, if necessary, modification of current recommendations.