Correction: A randomized controlled trial of nitrate supplementation in well-trained middle and older-aged adults.

[This corrects the article DOI: 10.1371/journal.pone.0235047.].

A randomized controlled trial of nitrate supplementation in well-trained middle and older-aged adults.

PURPOSE: Nitrate (NO3-), through its conversion to nitrite (NO2-) and nitric oxide, has been shown to increase exercise tolerance in healthy younger adults and older diseased patients. Nitrate's effect in well-trained middle to older-aged adults has not been studied. Therefore, the purpose of this investigation was to examine the effects of a NO3- rich beverage on submaximal constant work rate exercise time in well-trained middle to older-aged adults. METHODS: This was a randomized controlled cross-over trial with 15 well-trained middle to older-aged adults, 41-64 year-old, who received one of two treatments (NO3- rich beverage then placebo or placebo then NO3- rich beverage), after which an exercise test at 75 percent of the subject's maximal work rate was completed. RESULTS: The NO3- rich beverage increased plasma NO3- and NO2- levels by 260 µM and 0.47 µM, respectively (p<0.001). Exercise time was not significantly different (p = 0.31) between the NO3- rich versus placebo conditions (1130±151 vs 1060±132 sec, respectively). Changes in exercise time between the two conditions ranged from a 55% improvement to a 40% decrease with the NO3- rich beverage. Oxygen consumption and rating of perceived exertion were not significantly different between the two conditions. CONCLUSION: In middle to older-aged well-trained adults, NO3- supplementation has non-significant, albeit highly variable, effects on exercise tolerance. ClinicalTrials.gov Identifier: NCT03371966.

A randomized pilot study of nitrate supplementation with beetroot juice in acute respiratory failure.

Nitrate rich beetroot juice (BRJ) can enhance nitric oxide signaling, leading to improved physical function in healthy and diseased populations, but its safety and biologic efficacy have not been evaluated in a critically ill population. We randomized 22 previously functional acute respiratory failure patients to either BRJ or placebo daily until day 14 or discharge. We measured blood nitrate and nitrite levels and quantified strength and physical function at intensive care unit (ICU) and hospital discharge. Participants were predominantly male (54%), aged 68.5 years with an APACHE III score of 62. BRJ increased plasma nitrate (mean 219.2 µM increase, p = 0.002) and nitrite levels (mean 0.144 µM increase, p = 0.02). We identified no adverse events. The unadjusted and adjusted effect sizes of the intervention on the short physical performance battery were small (d = 0.12 and d = 0.17, respectively). In this pilot trial, administration of BRJ was feasible and safe, increased blood nitrate and nitrate levels, but had a small effect on physical function. Future studies could evaluate the clinical efficacy of BRJ as a therapy to improve physical function in survivors of critical illness.