A reverse J-shaped association between carbohydrate intake and mortality among populations with high carbohydrate...

Limited evidence exists on the associations of carbohydrate intake, both in quantity and quality, with mortality in high-carbohydrate populations, particularly in relation to the type of fat replacing carbohydrates. We investigated these associations in relation to all-cause, cancer-specific, and cardiovascular disease (CVD) mortality in a large Korean cohort.

A total of 113,043 participants aged 40-69 years were included from the Health Examinees-Gem (HEXA-G) cohort of the Korean Genome and Epidemiology Study (KoGES). Dietary intake was assessed using a validated food frequency questionnaire (FFQ). Cox proportional hazards regression models were used to estimate hazard ratios (HRs) and 95 % confidence intervals (CIs) for all-cause, cancer-specific, and CVD mortality.

During a mean follow-up of 9.2 years, 2,009 deaths were documented, including 1035 from cancer and 304 from CVD. When considering isocaloric substitution of fat with carbohydrates, a reverse J-shaped association was observed between carbohydrate intake and mortality from all causes and CVD. Compared with 55-<65 % of energy from carbohydrates, the HRs (95 % CIs) for all-cause mortality were 1.50 (1.09-2.06) for <55 %, 0.90 (0.74-1.08) for 65-<70 %, 0.96 (0.78-1.18) for 70-<75 %, 0.96 (0.76-1.21) for 75-<80 %, and 0.94 (0.71-1.24) for ≥80 % (P for trend = 0.16). Similarly, CVD mortality risk was significantly higher among participants with <55 % of energy intake from carbohydrates (HR: 3.04; 95 % CI: 1.44-6.43), compared with those with 55-<65 %. These findings were consistent across fat subtypes when carbohydrates replaced saturated, monounsaturated, or polyunsaturated fatty acids. No significant associations were observed between carbohydrate intake and cancer mortality. Regarding carbohydrate quality, no clear associations were found between dietary glycemic index or glycemic load and all-cause, cancer, and CVD mortality.

In a population with a predominantly high-carbohydrate diet, replacing fat with <55 % of energy from carbohydrates was suggestive of increased risks of all-cause and CVD mortality, and these associations were consistent regardless of the type of fat replaced.