Acute dietary nitrate supplementation does not attenuate oxidative stress or the hemodynamic response during submaximal exercise in hypobaric hypoxia

Abstract

The purpose of this study was to investigate changes in oxidative stress, arterial oxygen saturation (SaO), blood pressure (BP), and heart rate (HR) during exercise in hypobaric hypoxia following acute dietary nitrate supplementation. Nine well-trained (maximal oxygen consumption, 60.8 ± 7.8 mL·kg·min) males (age, 29 ± 7 years) visited the laboratory on 3 occasions, each separated by 1 week. Visit 1 included a maximal aerobic cycling test and five 5-min increasing-intensity exercise bouts in a normobaric environment (1600 m). A single dose of either a nitrate-depleted placebo (PL) or a nitrate-rich beverage (NR; 12.8 mmol nitrate) was consumed 2.5 h prior to exercise during visits 2 and 3 (3500 m) in a double-blind, placebo-controlled, crossover study consisting of a 5-min cycling warm-up and 4 bouts, each 5 min in duration, separated by 4-min periods of passive rest. Exercise wattages were determined during visit 1 and corresponded to 25%, 40%, 50%, 60%, and 70% of normobaric maximal oxygen consumption. Catalase and 8-isoprostane were measured before and after exercise (immediately before and 1 h postexercise, respectively). NR increased plasma nitrite (1.53 ± 0.83 μmol·L) compared with PL (0.88 ± 0.56 μmol·L) (p < 0.05). In both conditions, postexercise (3500 m) 8-isoprostane (PL, 23.49 ± 3.38 to 60.90 ± 14.95 pg·mL; NR, 23.23 ± 4.12 to 52.11 ± 19.76 pg·mL) and catalase (PL, 63.89 ± 25.69 to 128.15 ± 41.80 mmol·min·mL; NR, 78.89 ± 30.95 to 109.96 ± 35.05 mmol·min·mL) were elevated compared with baseline resting values (p < 0.05). However, both 8-isoprostane and catalase were similar in the 2 groups (PL and NR) (p = 0.217 and p = 0.080, respectively). We concluded that an acute, pre-exercise dose of dietary nitrate yielded no beneficial changes in oxidative stress, SaO, BP, or HR in healthy, aerobically fit men exercising at 3500 m.

Potential Benefits of Nitrate Supplementation on Antioxidant Defense System and Blood Pressure Responses after Exercise Performance

“…In addition, in the acute group, the nitrate supplementation did not attenuate oxidative stress. These results corroborate an earlier study, which showed that acute dietary nitrate supplementation did not attenuate oxidative stress [18]. Therefore, chronic nitrate supplementation can be an alternative method for improving oxidative stress after physical exercise.…”

“…Likewise, there is little evidence on the influence of nitrate supplementation on oxidative stress in physical exercise. Carriker et al [18] showed that acute dietary nitrate supplementation does not attenuate oxidative stress during submaximal exercise. However, no study showed the effect of chronic nitrate supplementation on oxidative stress after exercise.…”

Antioxidant Responses in Hypertensive Postmenopausal Women after Acute Beetroot Juice Ingestion and Aerobic Exercise: Double Blind and Placebo‐Controlled Crossover Trial

“…The sample calculation was performed using G.Power 3.1, using as main variable the variation of catalase after BJ ingestion and exercise (−33:18 ± 35 nmol/min/mL) [30]. Therefore, we found that the minimum sample should be 12 (power of 0.80; effect size of 0.474; alpha of 0.05; 3 groups and 4 measures).…”

The benefits and risks of beetroot juice consumption: a systematic review

“…Additionally, several studies have found that BRJ improves exercise tolerance or rate of perceived exhaustion in normoxia (Aucouturier et al 2015;Bailey et al 2015;Balsalobre-Fern andez et al 2018;Breese et al 2013;Wylie, Kelly, Fulford, et al 2013) as well as hypoxia (Kelly et al 2014;Vanhatalo et al 2011). Other studies, however, have failed to show such an effect on oxidative stress (Carriker et al 2018), rate of fatigue or perceived exertion (de Castro, de Assis Manoel, et al 2019;Lee et al 2019).…”