Author(s): MCLELLAN, A., ROWLAND, S., ODONNELL, E., JAMES, L., CLIFFORD, T., BAILEY, S., Institution: LOUGHBOROUGH UNIVERSITY, Country: UNITED KINGDOM, Abstract-ID: 739

INTRODUCTION:
The dose-response effect of acute dietary nitrate supplementation on brachial systolic blood pressure and exercise capacity has been well documented. However, there is a paucity of data exploring the dose-response effects of nitrate on central blood pressure, pulse wave variables, flow mediated dilation, and endurance exercise performance determinants. Thus, the purpose of the current study was to investigate the acute effects of ingesting three doses of nitrate rich beetroot powder on various cardiovascular function and endurance performance markers.
METHODS:
Eighteen normotensive, healthy participants (mean ± SD: age 23 ± 4 yr, BMI 24 ± 3 kg/m2, systolic blood pressure 119 ± 4 mmHg, V̇O2Peak 46 ± 13 mL·kg-1·min-1) completed four experimental conditions in a double-blind, randomized design. The conditions were: control with no supplement, and beetroot powder providing 200 mg, 400 mg, or 800 mg nitrate. During each trial, brachial and central blood pressure, pulse wave variables, and flow mediated dilation were measured, and a venous blood sample was collected prior to and 2.5 h following supplement ingestion. A ramp incremental cycling test to exhaustion was completed post supplement ingestion for assessment of exercise economy (V̇O2-WR slope), gas exchange threshold (GET), respiratory compensation point (RCP), peak aerobic power (PAP) and V̇O2peak. All data were assessed using one-way linear mixed models.
RESULTS:
Plasma nitrate and nitrite significantly increased (P ≤ 0.001) from control after ingesting 200 mg, 400 mg, and 800 mg nitrate. There were significant main effects of supplement for central systolic blood pressure (P = 0.043), but post-hoc analyses revealed no significant between-condition differences (P ≥ 0.066). There were significant main effects for pulse wave parameters (P ≤ 0.048), with augmentation index and augmentation pressure lower than control following ingestion of 200 mg (∆: -4 ± 7 % and -2 ± 3 mmHg), 400 mg (∆: -7 ± 8 % and -2 ± 3 mmHg), and 800 mg (∆: -6 ± 6 % and -2 ± 2 mmHg) nitrate. There were main effects of supplement for the absolute and percentage changes in artery diameters during flow mediated dilation assessment (P ≤ 0.046), with an increased artery diameter from control after ingesting 400 mg nitrate (∆: 0.002 ± 0.069 mm, P = 0.048), but not 200 mg or 800 mg (P ≥ 0.05). There were no significant effects on peripheral blood pressure variables or V̇O2-WR slope, GET, RCP, PAP and V̇O2peak during the ramp incremental exercise test (P ≥ 0.05).
CONCLUSION:
Acute supplementation with a nitrate-rich beetroot powder improved pulse wave variables and endothelial function, but these variables exhibited different dose-response effects. Brachial blood pressure and determinants of endurance performance were not altered by nitrate ingestion. These findings improve our understanding of the effects of nitrate supplementation on cardiovascular function and exercise capacity in healthy adults.