Beetroot juice improves performance in recreational runners without participation of antioxidant activity: a randomized blind double and controlled study

Purpose: Beetroot improves the performance of athletes mainly due to the action of nitrate, but it is also rich in antioxidants, and this juice property has been little explored. Thus, this study investigated the effects of beetroot juice on physical performance, nitrite plasmatic and oxidative stress in recreational runners. Method: Eighteen males recreational runners (38.1 ± 8.1 years, VO2 max 55.4 ± 7.2 ml.kg.min) performed a test until exhaustion on a treadmill at 80% of the VO2 max two hours after ingested of 140 ml of beetroot juice (8.2 mmol of NO3-) or control drink in cross over fashion. Blood samples were performed at baseline (before supplementation), pre-exercise (2 hours after supplementation) and immediately post-exercise to analyze plasma nitrite (NO), total antioxidant capacity (TAC), malondialdehyde (MDA), creatine kinase (CK) and lactate dehydrogenase (LDH). Result: Running time to exhaustion was 17.5 ± 2.5% higher with juice intake (BTJ: 61.3 ± 18.4 vs. CON: 54.1 ± 19.5 minutes, p = 0.00). The increase in performance was accompanied by an increase in plasma nitrite pre-exercise (BTJ: 16.3 ± 7.4 μM vs. CON: 11.6 ± 5.0 μM, p = 0.00) and post-exercise (BTJ: 16.9 ± 4.7 μM, vs. 12.2 ± 7.4 μM, p = 0.00). There was no significant difference between groups in MDA, TAC, CK, LDH. Conclusion: Beetroot juice improvement of performance in a race test until exhaustion however without any antioxidant or oxidative stress participation. Trial registration number and date of registration: RBR-9ydn4bn, June 09, 2022.