Effects of chronic dietary nitrate supplementation on the hemodynamic response to dynamic exercise

Abstract

While acute treatment with beetroot juice (BRJ) containing nitrate (NO3 (-)) can lower systolic blood pressure (SBP), afterload, and myocardial O2 demand during submaximal exercise, effects of chronic supplementation with BRJ (containing a relatively low dose of NO3 (-), 400 mg) on cardiac output (CO), SBP, total peripheral resistance (TPR), and the work of the heart in response to dynamic exercise are not known. Thus, in 14 healthy males (22 ± 1 yr), we compared effects of 15 days of both BRJ and nitrate-depleted beetroot juice (NDBRJ) supplementation on plasma concentrations of NOx (NO3 (-)/NO2 (-)), SBP, diastolic blood pressure (DBP), mean arterial pressure (MAP), CO, TPR, and rate pressure product (RPP) at rest and during progressive cycling exercise. Endothelial function was also assessed via flow-mediated dilation (FMD). BRJ supplementation increased plasma NOx from 83.8 ± 13.8 to 167.6 ± 13.2 μM. Compared with NDBRJ, BRJ reduced SBP, DBP, MAP, and TPR at rest and during exercise (P < 0.05). In addition, RPP was decreased during exercise, while CO was increased, but only at rest and the 30% workload (P < 0.05). BRJ enhanced FMD-induced increases in brachial artery diameter (pre: 12.3 ± 1.6%; post: 17.8 ± 1.9%). We conclude that 1) chronic supplementation with BRJ lowers blood pressure and vascular resistance at rest and during exercise and attenuates RPP during exercise and 2) these effects may be due, in part, to enhanced endothelium-induced vasodilation in contracting skeletal muscle. Findings suggest that BRJ can act as a dietary nutraceutical capable of enhancing O2 delivery and reducing work of the heart, such that exercise can be performed at a given workload for a longer period of time before the onset of fatigue.

Medium-term effects of dietary nitrate supplementation on systolic and diastolic blood pressure in adults

“…25 The burden of hypertension is particularly important in developing countries where the 26 limited access to adequate treatments and health care and the concomitant occurrence of 27 communicable diseases and nutritional deficiencies increase the risk for disability and 28 cardiovascular fatal events [2].…”

“…Eight studies had a cross-over study design [7,16, 26]and the remaining five studies adopted a parallel study design [17][18][19]27,28]. Ten studies 129 used a double-blind placebo controlled design [7,16,18,[22][23][24][25][26][27][28]. The trials were conducted characteristics of the studies included in the analysis are presented in Table S1 of the online 133 supplementary material.…”

“…Participant characteristics: Five studies recruited young, non-smoking, healthy 135 participants [7,21,23,25,26], three studies were conducted in older healthy subjects [17,19,27],…”

“…Five studies investigated the effects of dietary nitrate and beetroot juice on 140 exercise performance and recruited primarily young, physically active men [7,21,23,25,26].…”

“…The 143 choice of the placebo varied between studies and included sodium chloride solutions (two 144 studies) [21,27], blackcurrant juice (two studies) [7,17], negative control (one study [19] and 145 nitrate-depleted beetroot juice (eight studies) [16,18,[22][23][24][25][26]28]. All solutions were given 146 orally.…”