Key result
An acute pre-exercise dose of dietary nitrate yielded no beneficial changes in oxidative stress, arterial oxygen saturation, blood pressure, or heart rate in healthy men exercising at 3500m.
Why the study?
Does acute dietary nitrate supplementation reduce oxidative stress or improve hemodynamic responses during submaximal exercise in hypobaric hypoxia in well-trained males?
RCT (n=9)
Double-blind
Crossover
No
Does acute dietary nitrate supplementation reduce oxidative stress or improve hemodynamic responses during submaximal exercise in hypobaric hypoxia in well-trained males?
Absolute Event Rate: 52.11% vs 60.9%
p-value: p=0.217
An acute pre-exercise dose of dietary nitrate does not yield beneficial changes in oxidative stress, oxygen saturation, or hemodynamics in healthy, aerobically fit men exercising at high altitude.
Acute nitrate shows no hypoxic exercise benefit; small trial leaves open any role for oxidative stress or hemodynamics at altitude.
The purpose of this study was to investigate changes in oxidative stress, arterial oxygen saturation (SaO 2 ), 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 −1 ·min −1 ) 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 −1 ) compared with PL (0.88 ± 0.56 μmol·L −1 ) (p < 0.05). In both conditions, postexercise (3500 m) 8-isoprostane (PL, 23.49 ± 3.38 to 60.90 ± 14.95 pg·mL −1 ; NR, 23.23 ± 4.12 to 52.11 ± 19.76 pg·mL −1 ) and catalase (PL, 63.89 ± 25.69 to 128.15 ± 41.80 mmol·min −1 ·mL −1 ; NR, 78.89 ± 30.95 to 109.96 ± 35.05 mmol·min −1 ·mL −1 ) 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 2 , BP, or HR in healthy, aerobically fit men exercising at 3500 m.
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Carriker et al. (2018) conducted an RCT in Healthy (n=9). Dietary nitrate (beetroot juice) vs. Nitrate-depleted placebo was evaluated on Plasma 8-isoprostane 1-hour post-exercise (pg/ml) (p=0.217). An acute pre-exercise dose of dietary nitrate yielded no beneficial changes in oxidative stress, arterial oxygen saturation, blood pressure, or heart rate in healthy men exercising at 3500m.
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