Total antioxidant capacity of the diet modulates the association between habitual nitrate intake and cardiovascular events: A longitudinal follow-up in Tehran Lipid and Glucose Study

Background Considering the lack of data on the association between habitual dietary intakes of nitrate (NO3-) and nitrite (NO2-) and cardiovascular events, we assessed possible effects of dietary NO3- and NO2-, in the context of total antioxidant capacity (TAC) of the diet, with the risk of cardiovascular (CVD) outcomes. Methods Adult men and women without CVD (n = 2369) were recruited from the Tehran Lipid and Glucose Study and were followed for a mean of 6.7 years. Dietary NO3- and NO2- intakes, as well as dietary TAC and nitric oxide (NO) index were assessed at baseline (2006-2008). Multivariable-adjusted Cox proportional hazards regression models were used to estimate risk of CVD above and below median of dietary intakes of NO3-/NO2- and dietary TAC and NO index. Due to a significant interaction between NO3-/NO2- intake and TAC, stratified analyses were done for < and ≥ median dietary TAC. Results Daily mean (SD) dietary NO3- and NO2- intakes were 460 (195) and 9.5 (3.9) mg; mean (SD) dietary TAC and NO index was 1406 (740) and 338 (197) μmol trolox equivalent (TE)/100 g. In subjects with lower dietary TAC, higher intake of NO3- (≥ 430 mg/d) was accompanied with an increased risk of CVD (HR = 3.28, 95% CI = 1.54-6.99). There were no significant associations between dietary intakes of NO2-, TAC of the diet and NO index with the occurrence of CVD events during the study follow-up. Conclusion High habitual intake of NO3-, in the context of low TAC of the food, may be associated with the risk of CVD outcomes.