Nitrate-Rich Red Spinach Extract Supplementation Increases Exhaled Nitric Oxide Levels and Enhances High-Intensity Exercise Tolerance in Humans

Abstract

Acute and chronic administration of dietary inorganic nitrate source, such as beetroot, can promote Nitric Oxide (NO) production via the nitrate-nitrite-NO pathway and improves exercise performance. However, whether NO3− rich red spinach extract (RSE) could prominently elicits similar effects remains unclear. The current study therefore evaluated the effects of chronic (15-day) NO3− rich RSE supplementation on resting blood pressure (BP) breath NO production and high-intensity exercise tolerance. Eleven healthy males were randomly allocated in a double-blind, crossover trial design to receive 15-day of red spinach extract (RSE; 4 g·day−1 containing ~6 mmol of NO3−) and placebo (maltodextrin), with a washout period of not less than 7 days separating each trial. On day 15 of supplementation, participants completed a resting fractional exhaled NO (FeNO) measurement prior to an exhaustive high intensity exercise. The systolic BP were significantly lowered, and FeNO levels were higher (p < 0.05; p < 0.001), following RSE trial (124 ± 3 mmHg; 41 ± 14 ppb), compared to the PRE (129 ± 4; 21 ± 5 ppb) and PLA treatment (128 ± 4 mmHg; 21 ± 6 ppb), respectively. The time-to-exhaustion (TTE) in the high-intensity exercise increased during the RSE (764 ± 221 s) compared the placebo (642 ± 198 s) (p = 0.024). These findings suggest chronic dietary NO3− supplementation from red spinach source reduces BP and demonstrated to be a practical ergogenic intervention, partly through improving nitric oxide bioavailability.