The aim of this study was to assess the impact of diet and active substances in beetroot juice on the parameters of oxidative stress, inflammation, and muscle damage as well as on the maximum rate of oxygen uptake (VO_2max) in elite fencers (10 women, 10 men). Athletes during four weeks realized dietary recommendations (ID) and, after that, diet with freeze-dried beetroot juice supplementation (ID&BEET). At baseline and after each stage, fasting antioxidants, biomarkers of oxidative stress, inflammation, and skeletal muscle damage were measured, and a VO_2max test was performed. Only after ID&BEET was a significant increase of VO_2max observed, and changes of this parameter were negatively related with changes of serum lactate dehydrogenase (∆LDH) activity, as well as with serum ∆β-carotene and malondialdehyde concentration (∆MDA). Additionally, positive relationships were observed between ∆β-carotene versus changes of the serum concentration of advanced oxidation protein products (∆AOPP), changes of serum glutathione peroxidase activity (∆GPx3) versus both changes of physical activity level and ∆LDH, as well as erythrocyte glutathione peroxidase activity (∆GPx1) versus ∆LDH. To summarize, we showed that long-term beetroot juice supplementation increases lipid peroxidation, and improvement of VO_2max after ID&BEET seems to be dependent on LDH activity, as well as on the serum concentration of MDA and β-carotene.

This study aimed at assessment of the long-term (4 weeks) metabolic effect of a diet with and without beetroot juice supplementation in fencers using the untargeted metabolomics method with the UPLC Q-TOF/MS system to carry out an analysis of urine samples. Ten women and 10 men underwent the cardiovascular fitness VO_2max test at baseline—(B) and after two stages of implementation of the dietary recommendations—the first 4 weeks without beetroot juice (D) and the second with 26 g/d of freeze-dried beetroot juice supplementation (D&J). The urine samples were collected one hour after the VO_2max test at B and after D and D&J. The meal before the VO_2max test after D&J contained beetroot juice, whereas to the meal at B and after D maltodextrin was added. Changes in metabolites and VO_2max were significant only for comparison of D versus D&J. During D and D&J, there were no significant changes in the physical activity level, body mass, and body composition. We observed significant changes in tyrosine and tryptophan metabolism, mainly associated with such neurotransmitter’s metabolism as: Serotonin, noradrenaline, and adrenaline. Changes in signal intensity of bile acid, AICAR, and 4-Hydroxynonenal (peroxidation of polyunsaturated fatty acids product) were also observed. The obtained results indicate that long-term beetroot juice supplementation induces considerable changes in metabolism.

OBJECTIVE: This study aimed to analyze the long-term (4 weeks) effect of a diet and beetroot juice supplementation on hematological parameters, glutathione peroxidase activity in erythrocytes (GPx), and physical performance in elite fencers. METHODS: The study included 20 fencers and was conducted during the preparatory phase. Fencers underwent the fitness VO2max test at baseline - (B) and after two stages of implementation of the dietary recommendations – the first 4 weeks without beetroot juice (D) and the second with 26 g/d of freeze dried beetroot juice supplementation (D&J). At B and after D and D&J fasting blood samples were collected. RESULTS: After D and D&J activities of GPx were significantly higher than those in B (p < 0.000, p = 0.005 – respectively). After D&J versus D significant increased red blood cells count (p = 0.038) and hemoglobin (p = 0.029), as well as decreased platelet count (p = 0.007), were observed. Additionally, after D&J versus B a higher level of mean platelet volume (p = 0.043), energy (p = 0.001), and carbohydrate intake (p < 0.000) were observed and a lower level of red cell distribution width (p = 0.006). CONCLUSION: Our findings provide evidence that long-time consumption of beetroot juice may improve some hematological parameters (red blood cells count, hemoglobin, platelet count, mean platelet volume) - one of the key elements of physical performance. However, seems to be that this effect is largely determined by an appropriate level of energy and nutrients intake.