Dietary nitrate (NO(3)(-)) supplementation with beetroot juice (BR) over 4-6 days has been shown to reduce the O(2) cost of submaximal exercise and to improve exercise tolerance. However, it is not known whether shorter (or longer) periods of supplementation have similar (or greater) effects. We therefore investigated the effects of acute and chronic NO(3)(-) supplementation on resting blood pressure (BP) and the physiological responses to moderate-intensity exercise and ramp incremental cycle exercise in eight healthy subjects. Following baseline tests, the subjects were assigned in a balanced crossover design to receive BR (0.5 l/day; 5.2 mmol of NO(3)(-)/day) and placebo (PL; 0.5 l/day low-calorie juice cordial) treatments. The exercise protocol (two moderate-intensity step tests followed by a ramp test) was repeated 2.5 h following first ingestion (0.5 liter) and after 5 and 15 days of BR and PL. Plasma nitrite concentration (baseline: 454 ± 81 nM) was significantly elevated (+39% at 2.5 h postingestion; +25% at 5 days; +46% at 15 days; P < 0.05) and systolic and diastolic BP (baseline: 127 ± 6 and 72 ± 5 mmHg, respectively) were reduced by ∼4% throughout the BR supplementation period (P < 0.05). Compared with PL, the steady-state Vo(2) during moderate exercise was reduced by ∼4% after 2.5 h and remained similarly reduced after 5 and 15 days of BR (P < 0.05). The ramp test peak power and the work rate at the gas exchange threshold (baseline: 322 ± 67 W and 89 ± 15 W, respectively) were elevated after 15 days of BR (331 ± 68 W and 105 ± 28 W; P < 0.05) but not PL (323 ± 68 W and 84 ± 18 W). These results indicate that dietary NO(3)(-) supplementation acutely reduces BP and the O(2) cost of submaximal exercise and that these effects are maintained for at least 15 days if supplementation is continued.
[Show abstract][Hide abstract] ABSTRACT: Inorganic nitrate is present at high levels in beetroot and celery, and in green leafy vegetables such as spinach and lettuce. Though long believed inert, nitrate can be reduced to nitrite in the human mouth and, further, under hypoxia and/or low pH, to nitric oxide. Dietary nitrate has thus been associated favorably with nitric-oxide-regulated processes including blood flow and energy metabolism. Indeed, the therapeutic potential of dietary nitrate in cardiovascular disease and metabolic syndrome-both aging-related medical disorders-has attracted considerable recent research interest. We and others have shown that dietary nitrate supplementation lowers the oxygen cost of human exercise, as less respiratory activity appears to be required for a set rate of skeletal muscle work. This striking observation predicts that nitrate benefits the energy metabolism of human muscle, increasing the efficiency of either mitochondrial ATP synthesis and/or of cellular ATP-consuming processes. In this mini-review, we evaluate experimental support for the dietary nitrate effects on muscle bioenergetics and we critically discuss the likelihood of nitric oxide as the molecular mediator of such effects.
Frontiers in Physiology 08/2015; 6:211. DOI:10.3389/fphys.2015.00211 · 3.53 Impact Factor
"A growing body of evidence demonstrates that dietary supplementation with inorganic nitrate (NO − 3 ) can enhance exercise capacity in healthy adults (Hoon, Johnson, Chapman, & Burke, 2013; Jones, 2014). Improvements in cycling, running and rowing have all been reported following ingestion of NO − 3 -rich beetroot juice (Hoon et al., 2014; Lansley et al., 2011; Vanhatalo et al., 2010). The physiological adaptations following supplementation are not attributable to the NO − 3 compound per se, but more likely due to its reduction into the multipurpose cell signalling nitric oxide (NO) molecule. "
"Similarly, BJ has been found to improve exercise performance (Bond et al. 2012; Lansley et al. 2011). Using either a chronic (~5–8 mmol per day over 3 days; Bailey et al. 2010) or an acute dose of beetroot juice (~5–8 mmol ingested 2.5 h prior to exercise; Lansley et al. 2011), studies have reported a 3–5 % reduction in submaximal ˙ VO 2 for a given workload, indicating increased efficiency of exercise (Bailey et al. 2009; Larsen et al. 2011; Vanhatalo et al. 2010). Other studies have reported improvement in cycling time-trial performance (Cermak et al. 2012; Lansley et al. 2011) following 5–11.2 "
[Show abstract][Hide abstract] ABSTRACT: Sodium phosphate (SP) and beetroot juice (BJ) supplementation was assessed on repeated-sprint ability (RSA).
Thirteen female team-sport participants completed four trials: (1) SP and BJ (SP + BJ), (2) SP and placebo (for BJ), (3) BJ and placebo (for SP) and (4) placebo (for SP + BJ), with ~21 days separating each trial. After each trial, participants performed a simulated team-game circuit (STGC) consisting of four 15 min quarters, with a 6 × 20-m repeated-sprint set performed at the start, half-time and end.
Total sprint times were between 0.95-1.30 and 0.83-1.12 s faster for each RSA set and 3.25 and 3.12 s faster overall (~5 % improvement) after SP compared with placebo and BJ, respectively (p = 0.02 for sets 1, 2 and overall; Cohen's effect size: d = -0.51 to -0.90 for all sets and overall). Additionally, total sprint times were 0.48 s faster after SP + BJ compared with placebo (set 2; p = 0.05, ~2 % improvement). Furthermore, best sprints were 0.13-0.23 and 0.15-0.20 s faster (~6 % improvement; p < 0.01) after SP compared with placebo and BJ, respectively, for all sets (d = -0.54 to -0.89).
SP improved RSA in team-sport, female athletes when fresh (set 1) and during the later sets of a STGC (sets 2 and 3). Specifically, total and best sprint times were faster after SP compared with placebo and BJ.
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