Dietary nitrate enhances arterial oxygen saturation after dynamic apnea

Breath-hold divers train to minimize their oxygen consumption to improve their apneic performance. Dietary nitrate has been shown to reduce the oxygen cost in a variety of situations, and our aim was to study its effect on arterial oxygen saturation (SaO₂ ) after dynamic apnea (DYN) performance. Fourteen healthy male apnea divers (aged 33 ± 11 years) received either 70 mL of concentrated nitrate-rich beetroot juice (BR) or placebo (PL) on different days. At 2.5 h after ingesting the juice, they were asked to perform 2 × 75 m DYN dives in a pool with 4.5-min recovery between dives. Each dive started after 2-min countdown and without any warm-up apneas, hyperventilation, or lung packing. SaO₂ and heart rate were measured via pulse oximetry for 90 s before and after each dive. Mean SaO₂ nadir values after the dives were 83.4 ± 10.8% with BR and 78.3 ± 11.0% with PL (P < 0.05). At 20-s post-dive, mean SaO₂ was 86.3 ± 10.6% with BR and 79.4 ± 10.2% with PL (P < 0.05). In conclusion, BR juice was found to elevate SaO₂ after 75-m DYN. These results suggest an oxygen conserving effect of dietary nitrate supplementation, which likely has a positive effect on maximal apnea performance.