Beetroot juice and exercise: pharmacodynamic and dose-response relationships

Abstract

Ϫ ] increased in a dose-dependent manner, with the peak changes occurring at approximately 2-3 h. Compared with PL, 70 ml BR did not alter the physiological responses to exercise. However, 140 and 280 ml BR reduced the steady-state oxygen (O2) uptake during moderateintensity exercise by 1.7% (P ϭ 0.06) and 3.0% (P Ͻ 0.05), whereas time-to-task failure was extended by 14% and 12% (both P Ͻ 0.05), respectively, compared with PL. The results indicate that whereas plasma [NO 2 Ϫ ] and the O2 cost of moderate-intensity exercise are altered dose dependently with NO 3 Ϫ -rich BR, there is no additional improvement in exercise tolerance after ingesting BR containing 16.8 compared with 8.4 mmol NO 3 Ϫ . These findings have important implications for the use of BR to enhance cardiovascular health and exercise performance in young adults.nitrate; nitrite; nitric oxide; blood pressure; exercise economy; O2 uptake; exercise tolerance NITRIC OXIDE (NO) IS A GASEOUS signaling molecule that modulates human physiological function via its role in, for example, the regulation of blood flow, neurotransmission, immune function, glucose and calcium homeostasis, muscle contractility, and mitochondrial respiration (9, 36). 1 NO is generated through the oxidation of the amino acid L-arginine Ϫ ] peaked 3 h postingestion, remained close to peak values until 5 h postingestion, and returned to baseline after 24 h (39). The systolic and diastolic BP and the mean arterial pressure (MAP) were reduced significantly, by ϳ10, ϳ8, and ϳ8 mmHg, respectively, at 2.5-3 h after BR intake. The same research group later reported a dose-dependent increase in plasma [ ] was accompanied by significant reductions in both systolic BP (of ϳ2, ϳ6, and ϳ9 mmHg, respectively) and diastolic BP (of ϳ4, ϳ4, and ϳ6 mmHg, respectively). However, since BR contains polyphenols and antioxidants, which can facilitate the synthesis of NO from NO 2 Ϫ in the stomach (30), it is unclear whether BP is similarly impacted when different doses of BR are ingested compared with equivalent doses of NO 3 Ϫ salts. Given the growing interest in dietary NO 3 Ϫ supplementation in the form of BR amongst athletes and the general population, it is important to determine the pharmacokinetic-pharmacodynamic relationship between different volumes of BR consumption and changes in plasma [NO 2 Ϫ ] and BP to establish an optimal dose for beneficial effects.Recent investigations suggest that dietary NO 3 Ϫ supplementation has the potential to influence human physiology beyond 1 This article is the topic of an Invited Editorial by L. Burke (5a).

Dietary nitrate supplementation enhances high-intensity running performance in moderate normobaric hypoxia, independent of aerobic fitness

“…Consistent with previous investigations, plasma nitrate and nitrite, and exhaled NO concentrations were significantly elevated following dietary nitrate supplementation [1,2,5,8,55,22,39,38], signifying an increase in the 'substrates' available for NO generation via the nitrate-nitrite-NO pathway [11]. Peak plasma nitrite concentration was 602 % higher in BRJ versus PLA, similar to Arnold et al [38] (775 %) (~ 7 mmol nitrate), but considerably greater than reported by Muggeridge et al [22] (134 %) (~ 5 mmol nitrate) and Vanhatalo et al [8] (150 %) (~ 9.3 mmol).…”

“…Finally, there is some evidence of a dose-response to nitrate supplementation [55,65,66], and it is possible that well-trained athletes may require a high nitrate dose to appreciably alter plasma nitrite concentration relative to untrained individuals [30]. Therefore, the high nitrate dose administered in this study relative to investigations which have not observed an effect of nitrate supplementation (~ 5 -7 mmol) [38][39][40] may have also contributed towards the consistent ergogenic effect observed here.…”

Two weeks of watermelon juice supplementation improves nitric oxide bioavailability but not endurance exercise performance in humans

“…Taken together, these findings suggest that watermelon juice supplementation might represent an effective nutritional intervention to increase nitric oxide production and bioavailability. deproteinised plasma) used in this study [43]. Therefore, the increase in nitric oxide synthesis after watermelon juice supplementation in this study was likely insufficient to evoke an improvement in cycling economy.…”

“…Specifically, they were asked to record food and drink intake for 5 days, starting two days prior to the first control trial and ending on the day of the final control trial. They were provided with a list of foods rich in nitrate and asked to avoid these foods whilst completing the food diary to avoid a potential confounding influence of dietary nitrate intake on the physiological and performance measurements completed in this study [43]. Subjects were instructed to replicate their diet for the final 5 days of the subsequent supplementation periods.…”

“…[nitrite] via chemiluminescence [43], and [L-arginine] and [L-citrulline] via high-performance liquid chromatography (see below for details). The resting pulse rate, blood pressure and plasma data are expressed as the mean values collected on the two visits for the control, watermelon juice and placebo trials.…”