ETD

• beetroot
• inflammation
• nitric oxide
• oxidative stress
• sports nutrition
• triathlon

Background: Triathlon is a multisport discipline that combines swimming, cycling and running performed sequentially in this order. The high physical demands of triathlon make meeting nutritional requirements challenging; consequently, triathletes often rely on nutritional supplements to enhance their performance. Beetroot (Beta vulgaris) is a natural source of inorganic nitrate (NO₃⁻) and, as a dietary supplement, has been shown to effectively elevate circulating nitric oxide (NO) concentrations. Literature reports and reviews have shown that dietary nitrates can enhance cardiorespiratory endurance in athletes by increasing muscle contraction efficiency and improving performance at both anaerobic threshold and maximal oxygen consumption (VO₂max) intensities over various distances. Furthermore, at submaximal intensities, dietary nitrates have been shown to increase time to exhaustion. Nitrite (NO₂⁻) and NO have also been shown to suppress radical formation and neutralize potentially damaging reactive oxygen (ROS) and nitrogen (RNS) species, suggesting that NO₃⁻ may also exhibit antioxidant properties.
Methods: NOBEET® is a dietary supplement that contains nitrate-rich beetroot extract (Trubeet®), L-citrulline and L-arginine as NO precursors. The present pilot study was designed as a randomized, cross-over trial with two 7-day periods (Beetroot Supplementation vs No treatment), separated by a 15-day washout. Biomarkers were evaluated at baseline (T0), 2h post-first dose (T1), and after 7 days (T2), including NO pathway (NOx, nitrite (NO2), iNOS, peroxynitrite, 3-nitrotyrosine (3-NT)), oxidative stress (ROS production, 8-isoprostane, SOD activity), and cytokines (IL-6, IL-10). A total of 10 male triathletes (mean age 48.1±9.8 years and BMI 23.9±2.2 kg/m²) participated in this study.
Results: No adverse events occurred. Acute supplementation (T1 vs T0) significantly increased 3-NT concentration. After 7 days of supplementation (T2 vs T0), significant increases of NOx in plasma and urine, iNOS, peroxynitrite, ROS and IL-6 were recorded. At T2, NOx in plasma and urine, iNOS, peroxynitrite and ROS production were significantly higher after Beetroot Supplementation compared to No treatment, with no significant differences for 3-NT, SOD, 8-isoprostane, IL-6, and IL-10.
Conclusions: Beetroot-based nitrate supplementation may enhance NO-related pathway in non-professional endurance athletes without inducing oxidative or inflammatory stress.