Dietary Intakes of Plant and Animal Nitrate and 5-Year Blood Pressure Changes

BACKGROUND: The long-term health impacts of dietary nitrate may depend on its food source, since coingested components differ between plant-based (eg, polyphenols) and animal-based (eg, heme iron) foods, likely directing nitrate toward distinct metabolic pathways and divergent vascular effects. We investigated whether plant- and animal-sourced nitrate intake showed different associations with 5-year blood pressure (BP) changes and whether these associations were modified by key coingested nutrients. METHODS: In a cohort of 2942 Chinese adults, dietary intake was assessed using a validated food frequency questionnaire. Systolic BP and diastolic BP were measured at baseline and after 5 years. Brachial-ankle pulse wave velocity was assessed at follow-up to define arterial stiffness. Linear and logistic regression models were used to estimate β-coefficients and odds ratios, respectively. RESULTS: Higher plant-sourced nitrate was associated with a greater 5-year SBP decline (β, -3.51 [95% CI, -5.89 to -1.13]) and lower arterial stiffness (odds ratio, 0.59 [95% CI, 0.35-0.98]). Conversely, higher animal-sourced nitrate was associated with diastolic BP increase (β, 1.95 [95% CI, 0.54-3.37]). In joint analyses using a 2×2 approach based on median intakes of each component, high intakes of both plant-sourced nitrate and polyphenols or vitamin C showed the strongest inverse associations with systolic BP change, whereas high intakes of both animal-sourced nitrate and heme iron showed the strongest positive associations with DBP change. CONCLUSIONS: The association between dietary nitrate and BP is determined by its food source and might be affected by accompanying nutrients, highlighting the importance of considering the complete dietary context in nutritional epidemiology.