Effects of Short-Term Sodium Nitrate versus Sodium Chloride Supplementation on Energy and Lipid Metabolism during High-Intensity Intermittent Exercise in Athletes

The aim of this study was to investigate the possible effects of chronic nitrate supplementation on the metabolites of energy metabolism during high-intensity, high-volume intermittent training (HIHVT). In this placebo-controlled double-blind study, 17 participants exercised 3 times a week on a cycle ergometer. Sodium nitrate or sodium chloride as the placebo was supplemented daily at 8.5 mg/kg body weight for 10 days. The training exercise consisted of a warm-up, a 45-min interval period, and a post-exercise period. Oxygen uptake, respiratory exchange ratio, and various parameters were measured in the venous blood and plasma. During training, the oxygen uptake and respiratory exchange ratio did not differ between the nitrate and the placebo group. Venous plasma concentrations of nitrate and nitrite were significantly increased in the nitrate group (p < 0.001 and p = 0.007, respectively). Triglyceride concentrations were significantly lower in the nitrate group than in the placebo group (p = 0.010). The concentration of free fatty acids in the plasma did not change upon nitrate supplementation and no significant differences were observed in the contribution of fat to energy metabolism during exercise. An increase in plasma ammonia concentration was observed in the nitrate group during and after exercise (p = 0.048). Metabolites of energy-rich phosphates did not differ between the nitrate and chloride groups, suggesting no improvement in efficiency through the supplemented nitrate. It was concluded that nitrate supplementation did not reduce oxygen uptake and adenosine triphosphate resynthesis by hydrolysis or through creatine kinase activity during high-intensity, high-volume intermittent exercise. Although, lipid metabolism as well as amino acid metabolism might be affected by nitrate supplementation during HIHVT.