Thematic review series: Patient-Oriented Research. Dietary fat, carbohydrate, and protein: effects on plasma lipoprotein patterns

Alice H Lichtenstein

doi:10.1194/jlr.r600019-jlr200

Abstract

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.

Highlights

METHODOLOGICAL ISSUESThere are a considerable number of methodological challenges associated with studies designed to assess the effect of diet composition on lipoprotein patterns
Under isoweight conditions, different types of dietary protein or individual amino acids have little effect on lipoprotein patterns
It is difficult to consider the independent effect of dietary fat, carbohydrate, or protein on plasma lipoprotein patterns because, in each case, in addition to contributing unique essential and nonessential nutrients, the macronutrients contribute the majority of metabolic energy to sustain life

Summary

METHODOLOGICAL ISSUES

There are a considerable number of methodological challenges associated with studies designed to assess the effect of diet composition on lipoprotein patterns. Metabolism varies by gender and age, and within each of these categories, multiple changes (e.g., hormonal and body composition) proceed at different rates, making them difficult to factor into the final analysis. With respect to nonhuman interventions, there is no ideal animal model, transgenic or knockout, or in vitro system that yields data consistently analogous to human data. This is attributable to inherent differences in such factors as the physiology of gastrointestinal tracts, the characteristics of endocrine and immune systems, the pathways and nature of lipoprotein metabolism, and differences in body composition and metabolic rates. Critical data have emerged from animal and in vitro systems, with respect to questions that cannot be adequately addressed in humans, these data need to be treated as pieces of the puzzle, critical but considered with caution when out of context

Stable body weight

Body weight change

Dietary fatty acids

Dietary cholesterol

CONCLUSIONS