The Effects of Dietary Nitrate on Oxygen Consumption in College Aged Males

Abstract

**Please note that the full text is embargoed** ABSTRACT: INTRODUCTION: Nitrate (NO3-) is an inorganic polyatomic ion readily available in foods such as lettuce, celery, spinach, and beetroot. Once ingested nitrate is ultimately converted into nitric oxide (NO) by several metabolic pathways. NO is a well-known vasodilator which has been shown to improve exercise performance. Therefore, several researchers have studied the effects of dietary nitrate on exercise performance. Additionally, dietary nitrate supplementation has exhibited the ability to reduce the body's oxygen demand during submaximal work. The Bruce protocol is an incremental maximal exercise test used to determine oxygen consumption. PURPOSE: The purpose of this study was to examine the effects of dietary nitrate on maximal oxygen consumption. METHODS: Five men (age 24 ± 5.7 yrs.) from the University of Texas at Arlington volunteered to participate in this study. The subjects either ingested 70ml of Beet It Sport Shot (400mg of nitrates) or 70ml of a Placebo (black cherry Kool-Aid) for three days and then performed a Bruce protocol maximal exercise test in which the speed and grade progressively increased until the subject reached exhaustion. The subjects were then asked to return and consume the opposite of the two drinks for three days and perform the Bruce protocol again. During each test, maximum oxygen consumption (VO2max), time to exhaustion, the rate of perceived exhaustion (RPE), and maximal heart rate (HRmax) were recorded. The alpha level for significance was set at p < 0.05. RESULTS: Five men: age 24 ± 5.7 yrs., height 182 ± 9.0 cm, and weight 82 ± 8.5 kg. The maximal values for the subjects with the placebo were: VO2max = 47.4 ml/kg/min ± 8.2, time to fatigue = 12.9 min ± 1.9, RPE = 17.4 ± 1.7, HRmax= 189.4 bpm ± 5.7. The values for the subjects with beetroot supplement were: VO2max = 50.4 ml/kg/min ± 7.2, time to fatigue = 13.1 min ± 2.0, RPE = 16.6 ± 1.67, HRmax = 187.8 bpm ± 5.9. Statistical analysis between the two conditions indicated that there were no significant differences (p > 0.05). CONCLUSION: The results of this study indicate that there was no significant difference between VO2max with or without beetroot supplement in this group (p= 0.55). Additionally, there was no significant difference in time to exhaustion (p= 0.86). Previous studies that have provided larger amounts of beetroot juice for longer periods of time have demonstrated improvement in maximal exercise. Therefore, the lower amounts of beetroot consumed for a short period of time may have impacted the results.