Acute Dietary Nitrate Supplementation And Cold Pressor Test Cardiovascular Responses In Young Women

Research specific to acute nutritional interventions that alter cardiovascular responses to stress in young women, is lacking. Beet root juice (BRJ) is highly concentrated with dietary nitrate which is a precursor to the compound nitric oxide (NO). NO is a potent vasodilator and has vascular health implications. PURPOSE: The purpose of this study was to investigate the influence of acute BRJ supplementation on cardiovascular responses to a cold pressor test (CPT) in young women. METHODS: 17 (aged 18-23) women completed this placebo-controlled, counter-balanced, crossover protocol. Participants completed 3 laboratory visits (familiarization & 2 experimental). Experimental visits differed in the BRJ formula; whereby the placebo had nitrate removed by the manufacturer. Heart rate (HR), blood pressure (MAP = 1/3 SBP + 2/3 DBP), and rate pressure product [RPP = (HR⸱SBP)⸱0.01] were monitored immediately prior (pre), after (post), and during a 4-minute recovery window following a CPT. A mixed-model, linear regression with fixed factors of time (post, 1-min, 2-min, 3-min, 4-min) and treatment (placebo vs. experimental) were used to explore mean differences in dependent variables (MAP, HR, & RPP). Additionally, pre-measures of HR, MAP, and RPP were used as covariates to account for daily variation. Sidak adjustments were implemented if pairwise comparisons were warranted (α ≤ 0.05). RESULTS: Regression results revealed no interaction (all p > 0.26) nor main effect of treatment (all p > 0.40) for HR, MAP, or RPP. However, as expected, there was a main effect of time (all p < 0.001); whereby minute 0 was higher than minutes 1, 2, 3, and 4 during the recovery window for HR (adjusted mean ± SE; 0-min = 84 ± 1.4 bpm, 1-min = 74 ± 1.4 bpm, 2-min = 75 ± 1.4 bpm, 3-min = 76 ± 1.4 bpm, 4-min = 76 ± 1.4 bpm) and RPP (adjusted mean ± SE; 0-min = 116 ± 2.0 au, 1-min = 87 ± 2.0 au, 2-min = 83 ± 2.0 au, 3-min = 82 ± 2.0 bpm, 4-min = 83 ± 2 au) but no differences in other pairwise comparisons (p > 0.05). Furthermore, MAP (adjusted mean ± SE; 0-min = 107 ± 1.5 mmHg, 1-min = 88 ± 1.5 mmHg, 2-min = 82 ± 1.5 mmHg, 3-min = 80 ± 1.5 mmHg, 4-min = 80 ± 1.5 mmHg) for minutes 0 and 1 were higher than minutes 2, 3, & 4 (all p < 0.001) with no differences in other pairwise comparisons (p > 0.05). CONCLUSIONS: BRJ did not influence cardiovascular reactivity following a cold pressor test when compared to placebo.