Influence of dietary nitrate food forms on nitrate metabolism and blood pressure in healthy normotensive adults.
Level 2 - randomized trial
Individual randomized controlled crossover trial
PubMed 29223585 · doi:10.1016/j.niox.2017.12.001
What was done
Ten healthy male participants ingested equimolar doses of inorganic nitrate (~5.76 mmol) delivered in three distinct food vehicles: 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). These were compared against a lower-dose soluble beetroot crystal drink (BC, ~1.40 mmol nitrate) and a deionized water control (CON, 70 mL). Blood pressure and plasma, salivary, and urinary nitrate and nitrite concentrations were measured at baseline and monitored up to 24 hours post-ingestion.
What was found
All nitrate-rich food vehicles elevated plasma, salivary, and urinary nitric oxide metabolites relative to baseline and control (P < 0.05). Peak increases in plasma nitrite were greater in BF (371 ± 136 nM) and BR (369 ± 167 nM) compared to BL (283 ± 93 nM, P < 0.05) and BC (232 ± 51 nM). Only BR significantly reduced systolic blood pressure (~5 mmHg) and mean arterial pressure (~3–4 mmHg, P < 0.05). BF significantly reduced diastolic blood pressure (~4 mmHg, P < 0.05), whereas BL and BC showed no significant blood pressure reductions.
Why it matters
The physical vehicle and concentration of dietary nitrate influence acute vascular responses, showing that identical nitrate doses in different food matrices do not produce uniform blood pressure effects.
Limits
The trial had a very small sample size (n = 10) restricted exclusively to healthy, normotensive males. Only acute (24-hour) effects of single doses were assessed, leaving long-term efficacy and responses in clinical or hypertensive populations unmeasured.
Cited by
- contradicts Concentrated beetroot juice or extract begins taking effect within approximately five minutes and lasts for around three hours.