Associations of Lower-Carbohydrate and Lower-Fat Diets with Mortality among People with Cardiovascular Disease.

Background: Although low-carbohydrate and low-fat diets have been shown to have short-term metabolic benefits, the associations of these dietary patterns, particularly different food sources and macronutrient quality, with mortality in people with cardiovascular disease (CVD) remain unclear.

Objectives: To examine the associations of different types of lower-carbohydrate diets (LCDs) and lower-fat diets (LFDs) with mortality in individuals with CVD.

Methods: This study included 3971 adults with CVD from the NHANES 1999-2014. Mortality status was linked to National Death Index mortality data through 31 December 2019. Overall, unhealthy and healthy LCD and LFD scores were determined based on the percentages of energy from total and subtypes of carbohydrate, fat, and protein. Cox proportional hazards regression models were applied to calculate hazard ratios (HRs) and 95% confidence intervals (CIs).

Results: Higher healthy LCD score was associated with favorable blood lipids and higher homeostasis model assessment of insulin resistance, whereas higher unhealthy LFD score was associated with lower high-density lipoprotein and higher C-reactive protein at baseline (all P-trend < 0.05). During 35,150 person-years of follow-up, 2163 deaths occurred. For per 20-percentile increment in dietary scores, the multivariate-adjusted HRs of all-cause mortality were 0.91 (95% CI: 0.86, 0.96) for healthy LCD score (P < 0.001), 0.94 (95% CI: 0.89, 1.00) for healthy LFD score (P = 0.04), and 1.07 (95% CI: 1.00, 1.14) for unhealthy LFD score (P = 0.04).

Conclusions: Overall LCD and LFD scores are not associated with total mortality. Unhealthy LFD scores are associated with higher total mortality, whereas healthy LCD and LFD scores are associated with lower mortality in people with CVD.