Saturated fat, carbohydrate, and cardiovascular disease

Abstract

A focus of dietary recommendations for cardiovascular disease (CVD) prevention and treatment has been a reduction in saturated fat intake, primarily as a means of lowering LDL-cholesterol concentrations. However, the evidence that supports a reduction in saturated fat intake must be evaluated in the context of replacement by other macronutrients. Clinical trials that replaced saturated fat with polyunsaturated fat have generally shown a reduction in CVD events, although several studies showed no effects. An independent association of saturated fat intake with CVD risk has not been consistently shown in prospective epidemiologic studies, although some have provided evidence of an increased risk in young individuals and in women. Replacement of saturated fat by polyunsaturated or monounsaturated fat lowers both LDL and HDL cholesterol. However, replacement with a higher carbohydrate intake, particularly refined carbohydrate, can exacerbate the atherogenic dyslipidemia associated with insulin resistance and obesity that includes increased triglycerides, small LDL particles, and reduced HDL cholesterol. In summary, although substitution of dietary polyunsaturated fat for saturated fat has been shown to lower CVD risk, there are few epidemiologic or clinical trial data to support a benefit of replacing saturated fat with carbohydrate. Furthermore, particularly given the differential effects of dietary saturated fats and carbohydrates on concentrations of larger and smaller LDL particles, respectively, dietary efforts to improve the increasing burden of CVD risk associated with atherogenic dyslipidemia should primarily emphasize the limitation of refined carbohydrate intakes and a reduction in excess adiposity.

FIGURE 1

Mean (±SEM) effects of variation in dietary carbohydrate and saturated fat on LDL subclasses. A cohort of 178 men were randomly assigned to 1 of 4 diet groups: diets with varying carbohydrate contents (54%, 39%, or 26% of total energy) and a low saturated fat content (•, 8% of total energy derived primarily from dairy products) or a diet with a relatively low carbohydrate (26%) and a high saturated fat content (□, 15% of total energy) (8). In the context of the 26% carbohydrate diet, high dietary saturated fat was associated with increases in large and medium LDL, but not with small LDL, relative to diets with a lower saturated fat content. Data points represent biochemical profiles for each of the 4 dietary groups. Values are the total lipoprotein mass as measured by analytic ultracentrifugation.