Association of Low-Carbohydrate and Low-Fat Diets With Mortality Among US Adults

IMPORTANCE: It is crucial to incorporate quality and types of carbohydrate and fat when investigating the associations of low-fat and low-carbohydrate diets with mortality. OBJECTIVE: To investigate the associations of low-carbohydrate and low-fat diets with total and cause-specific mortality among US adults. DESIGN, SETTING, AND PARTICIPANTS: This prospective cohort study used data from the US National Health and Nutrition Examination Survey from 1999 to 2014 from 37 233 adults 20 years or older with 24-hour dietary recall data. Data were analyzed from July 5 to August 27, 2019. EXPOSURES: Overall, unhealthy, and healthy low-carbohydrate-diet and low-fat-diet scores based on the percentage of energy as total and subtypes of carbohydrate, fat, and protein. MAIN OUTCOMES AND MEASURES: All-cause mortality from baseline until December 31, 2015, linked to National Death Index mortality data. RESULTS: A total of 37 233 US adults (mean [SD] age, 49.7 [18.3] years; 19 598 [52.6%] female) were included in the present analysis. During 297 768 person-years of follow-up, 4866 total deaths occurred. Overall low-carbohydrate-diet and low-fat-diet scores were not associated with total mortality. The multivariable-adjusted hazard ratios for total mortality per 20-percentile increase in dietary scores were 1.07 (95% CI, 1.02-1.11; P = .01 for trend) for unhealthy low-carbohydrate-diet score, 0.91 (95% CI, 0.87-0.95; P