Impact of carbohydrate quality on the association between low-carbohydrate diet scores and longitudinal changes of cardiometabolic risk factors

While low-carbohydrate diet (LCD) patterns have been promoted to improve cardiometabolic risk factors, evidence from long-term studies on the impact of carbohydrate quality in these diets remains equivocal. We examined long-term associations among LCD patterns varying in carbohydrate quality and changes in cardiometabolic risk factors. Dietary, health and lifestyle data were collected from Framingham Offspring cohort participants (n = 3294) every 4 years over a median 16.4-year follow-up. We assessed LCD patterns using 2 LCD scores (LCDSs) reflecting higher total fat and protein intake, and lower intake of (i) low-quality carbohydrates (high-quality LCDS, HQ-LCDS) and (ii) high-quality carbohydrates (low-quality LCDS, LQ-LCDS). Adjusted means of annualized changes in cardiometabolic risk factors across quintiles of LCDSs were estimated using repeated measures linear models. Baseline median age was 55 years, with 54% female participants. Waist circumference annual gains (cm/y) increased across quintiles (mean for Quintile 1, Quintile 5; P-trend) for HQ-LCDS (0.58, 0.69; 0.004), and LQ-LCDS (0.56, 0.74; <0.001). A slower annual increase in systolic blood pressure (mmHg/y) observed for HQ-LCDS (0.16, 0.00; 0.03), and LQ-LCDS (0.21, -0.05; 0.01). Higher HQ-LCDS was associated with a greater annual increase in HDL cholesterol concentrations (mg/dL/y) (0.51, 0.68; 0.005) and greater annual decline in triglyceride concentrations (mg/dL/y) (-1.24, -1.99; <0.001). Although both high- and low-quality LCD patterns were associated with greater increases in waist circumference, our findings support recommendations to preserve high-quality carbohydrate in the context of low-carbohydrate diets and to replace low-quality carbohydrate with more healthy energy sources.