Moderate dose of watercress and red radish does not reduce oxygen consumption during graded exhaustive exercise

Objective: Very recent studies have reported positive effects of dietary nitrate on the oxygen consumption during exercise. This research aimed to study the effect of moderate dose of high-nitrate vegetables, watercress (Nasturtium officinale) and red radish (Raphanus sativus) compared with a control group on the incremental treadmill exercise test following a standard Bruce protocol controlled by computer. Materials and Methods: Group 1 consumed 100 g watercress (n=11, 109.5 mg nitrate/day), and group 2 consumed 100 g red radish (n=11, mg 173.2 mg nitrate/day) for seven days, and control group (n=14) was prohibited from high nitrate intake. Results: During exercise, watercress group showed significant changes in the maximum values of Respiratory Exchange Ratio (RER) (p<0.05), End-Tidal O(2) Fraction (FETO(2)) (p<0.05), and energy consumption from carbohydrate (p<0.01). Red radish group had a significant increase in the VCO(2) (p<0.01), RER (p<0.01), VT (p<0.05), VCO(2)/kg (p<0.05), and energy consumption from carbohydrates (p<0.01). When all groups in the same workload were normalized by the subject’s body mass, watercress had a significant increase in the total expired CO(2 )(p<0.05), RER (p<0.05), FETO(2) (p<0.05), and energy consumption from carbohydrates (p<0.05) compared with the control group. Similar comparison between red radish and control group revealed a significant increase during pre-test in the total CO(2) production (p<0.05), VCO(2) (p<0.05), RER (p<0.01), VT (p<0.05), and VCO(2)/kg (p<0.05). Conclusion : Current results indicate higher carbon dioxide production in the experimental groups in the same workload. This might have a negative impact on the exercise performance. Further investigations with controlled exercise program will be necessary.