Pharmacokinetics of Nitrate and Nitrite Following Beetroot Juice Drink Consumption

Background: Nitrate (NO3-)-rich beetroot (BR) juice supplementation has been shown to improve cardiovascular function via reduction to nitrite (NO2-) and then to the bioactive molecule nitric oxide (NO). However, limited research exists for the role of inorganic NO2- that is contained naturally within BR. Objective: As BR juice can naturally contain both NO3- and NO2- the objective of this study was to evaluate the individual effects of NO3- and NO2- consumed from BR on plasma [NO3-]/[NO2-] and their subsequent effects on various cardiovascular measures. Design: In four separate treatments, 11 healthy adults consumed 250 mL of BR containing one of the following: (i) high NO3-, low NO2- (HL; 572 mg NO3-, 32 mg NO2-); (ii) medium NO3-, medium NO2- (MM; 280 mg NO3-, 237 mg NO2-); (iii) low NO3-, medium NO2- (LM; 43 mg NO3-, 262 mg NO2-); (iv) placebo (PL; low NO3-, low NO2-: 8 mg NO3-, 5.8 mg NO2-). Plasma [NO3-]/[NO2-], blood pressure, heart rate, mean arterial pressure (MAP), cardiac output and stroke volume were measured at baseline and every hour or second hour for 6 h post-BR consumption. Outcomes: Ingestion of the HL and MM BR increased plasma [NO2-] and [NO3-] after 2 h, with both remaining elevated after 6 h (p < 0.05). LM increased plasma [NO3-] (p < 0.05) but did not increase plasma [NO2-] compared to PL (p = 0.177). MAP was lower following the consumption of HL at 4 h and LM at 6 h (p < 0.05). Conclusion: Inorganic NO3- consumption is the critical factor in elevating plasma [NO3-] and [NO2-]; however, both NO2- and NO3- show potential to reduce MAP. The known reduction of systolic blood pressure (SBP)/diastolic blood pressure (DBP) following NO3- supplementation was not observed, making it unclear if NO2- contributes to a reduction in SBP/DBP alongside NO3-.

Automated summary

This study found that the ingestion of inorganic nitrate in beetroot juice is a critical factor in elevating plasma nitrate and nitrite levels. Both nitrate and nitrite have potential to reduce mean arterial pressure, with high nitrate concentration leading to significant reductions in mean arterial pressure in a shorter period of time. However, it is currently unclear whether nitrite contributes to the reduction in blood pressure.