Influence of acute dietary nitrate supplementation timing on nitrate metabolism, central and peripheral blood pressure and exercise tolerance in young men.
Level 2 - randomized trial
Individual randomized crossover trial
PubMed 38040982 · doi:10.1007/s00421-023-05369-z
What was done
Twelve males completed six experimental visits in a repeated-measures crossover design. Participants ingested nitrate-rich beetroot juice (~13 mmol nitrate) or nitrate-depleted beetroot juice placebo across three timepoints: morning, afternoon, and evening. Researchers measured salivary flow rate, salivary pH, salivary and plasma nitrate/nitrite concentrations, and brachial and central systolic blood pressure before and after supplementation, followed by a severe-intensity cycling time-to-exhaustion test.
What was found
No significant differences were observed between timing conditions for mean salivary flow rate or salivary pH. Plasma nitrite elevations following nitrate ingestion did not differ among morning, afternoon, and evening trials. Brachial systolic blood pressure was unchanged following nitrate supplementation across all conditions. Central systolic blood pressure decreased similarly across all timepoints: morning (-3 ± 4 mmHg), afternoon (-4 ± 3 mmHg), and evening (-2 ± 3 mmHg). Cycling time to exhaustion did not differ between nitrate and placebo at any timepoint.
Why it matters
These findings suggest that diurnal variations in salivary physiology do not meaningfully alter acute nitrate metabolism or its central blood pressure-lowering effect, showing that acute nitrate supplementation does not need to be timed to specific parts of the day.
Limits
The study had a very small sample size (n = 12) restricted entirely to young males. The investigation assessed only acute, single-dose supplementation, precluding conclusions about chronic dosing schedules or performance in trained athletes or clinical populations.
Cited by
- contradicts Concentrated beetroot juice or extract begins taking effect within approximately five minutes and lasts for around three hours.