Influence of dietary nitrate food forms on nitrate metabolism and blood pressure in healthy normotensive adults.

ABSTRACT

Inorganic nitrate (NO3-) supplementation has been shown to improve cardiovascular health indices in healthy adults. The purpose of this study was to investigate how the vehicle of NO3- administration can influence NO3- metabolism and the subsequent blood pressure response. Ten healthy males consumed an acute equimolar dose of NO3- (∼5.76 mmol) in the form of a concentrated beetroot juice drink (BR; 55 mL), a non-concentrated beetroot juice drink (BL; 456 mL) and a solid beetroot flapjack (BF; 60 g). A drink containing soluble beetroot crystals (BC; ∼1.40 mmol NO3-) and a control drink (CON; 70 mL deionised water) were also ingested. BP and plasma, salivary and urinary [NO3-] and [NO2-] were determined before and up to 24 h after ingestion. All NO3--rich vehicles elevated plasma, salivary and urinary nitric oxide metabolites compared with baseline and CON (P<0.05). The peak increases in plasma [NO2-] were greater in BF (371 ± 136 nM) and BR (369 ± 167 nM) compared to BL (283 ± 93 nM; all P<0.05) and BC (232 ± 51 nM). BR, but not BF, BL and BC, reduced systolic (∼5 mmHg) and mean arterial pressure (∼3-4 mmHg; P<0.05), whereas BF reduced diastolic BP (∼4 mmHg; P < 0.05). Although plasma [NO2-] was elevated in all conditions, the consumption of a small, concentrated NO3--rich fluid (BR) was the most effective means of reducing BP. These findings have implications for the use of dietary NO3-supplements when the main objective is to maintain or improve indices of cardiovascular health.