Association of total and source-specific dietary nitrate and nitrite with subclinical atherosclerosis in young adults

Atherosclerosis, a chronic process originating in young adulthood and progressing silently to clinical cardiovascular disease, highlights the need to identify modifiable nutritional exposures. Epidemiological evidence regarding their association with subclinical atherosclerosis in young populations remains limited. This study aimed to investigate the association between total and source-specific (natural versus processed) dietary nitrate and nitrite intake with carotid intima-media thickness (CIMT) in young adults. This cross-sectional analysis included 932 adults aged 20–40 years from the sixth phase of the Tehran Lipid and Glucose Study (2015–2018) with complete dietary data and CIMT measurements. Dietary nitrate and nitrite intakes were estimated using a validated food frequency questionnaire linked to a nationally developed nitrate/nitrite database. Dietary nitrite/nitrate intakes were categorized based on from natural and processed foods. CIMT was measured using an ultrasound examination. Multivariate-adjusted linear and logistic regression was used to determine the association of dietary nitrite/nitrate with CIMT. High CIMT was defined as ≥ 90th percentile for age and sex. The mean age of participants was 28.2 ± 4.25 years (51% men). In crude linear regression, total nitrate intake was inversely associated with CIMT (β =-0.003; 95% CI:-0.005, -0.001; P = 0.003); however, this association was attenuated after adjustment for confounding factors. For processed-source nitrite, participants in the highest tertile demonstrated significantly higher odds of elevated CIMT in crude analysis (OR = 1.80; 95% CI:1.20–2.72; P trend =0.004) and after lifestyle adjustment (OR = 1.62; 95% CI:1.01–2.59; P trend =0.04), but this association was attenuated following adjustment for CVD risk score and BMI (OR = 1.49; 95% CI:0.92–2.41; P trend =0.10). Notably, nitrate intake exceeding the acceptable daily intake (ADI) threshold was independently associated with reduced odds of high CIMT in fully adjusted models (OR per 100 mg above ADI = 0.87; 95% CI:0.76–0.99). Our findings showed that dietary nitrite/nitrate intake whether from the natural or processed food sources were not associated with CIMT. High dietary intake of total nitrate, per 100 mg exceeding ADI, inversely associated with the risk of high CIMT.