Effects of dietary nitrate on respiratory physiology at high altitude - Results from the Xtreme Alps study
Cumpstey AF, Hennis PJ, Gilbert-Kawai ET, Fernandez BO, Poudevigne M, Cobb A, Meale P, Mitchell K, Moyses H, Pöhnl H, Mythen MG, Grocott MPW, Feelisch M, Martin DS, Xtreme Alps research group
Nitric oxide : biology and chemistry · 17 citations
Review labels
Neutral facts our review recorded about how this study was done. They describe method, never whether we like the result.
How it was studied
- Design
- Randomized controlled trial (classified by our AI screen)
- Studied in
- People
- Main outcome
- Health markers and function
- Intake measured by
- Not stated
Who paid for it
- Funding
- Industry funded
- Government
- National Institute for Health and Care Research
- University or hospital
- University of Southampton
- University or hospital
- University College London
- Government
- Medical Research Council
- Government
- National Institute for Health Research (NIHR)
- Authors
- At least one author declares a financial tie to industry
- Grants
- Medical Research Council (MR/P008887/1); National Institute for Health and Care Research (ACF-2015-26-003)
Based on 5 listed funder(s) and full-text disclosure statement.
Publication
- Published
- 2017-10-16 · Nitric Oxide · vol. 71 · pp. 57–68
- Publisher
- Elsevier BV
- Cited
- 17 citations · more than 84% of similar papers · 1.4× the field average
- References
- 74 works
- Access
- Open access (hybrid journal) · CC-BY
- Research areas
- High Altitude and Hypoxia · Neuroscience of respiration and sleep · Chronic Obstructive Pulmonary Disease (COPD) Research
- Keywords
- Nitrate, Nitrite, Exhaled breath condensate, Effects of high altitude on humans, Nitric oxide, Placebo, Hypoxia (environmental), Saliva, Exhaled nitric oxide, Animal science, Altitude (triangle), Altitude sickness, Chemistry, Internal medicine, Physiology, Medicine, Oxygen, Biology, Spirometry, Pathology
- MeSH
- lung, saliva, humans, beta vulgaris, altitude sickness, nitrates, nitrites, oxygen, nitric oxide, dietary supplements, adult, female, male, respiratory rate, fruit and vegetable juices
14 authors
From GB
- Andrew F. CumpsteySouthampton General Hospital; University Hospital Southampton NHS Foundation Trust; NIHR Southampton Respiratory Biomedical Research Unit; University of Southampton
- Philip J HennisUniversity College London
- Edward T. Gilbert-KawaiUniversity College London
- Bernadette O. FernandezUniversity Hospital Southampton NHS Foundation Trust; University of Warwick; NIHR Southampton Biomedical Research Centre; University of Southampton
- Matthieu PoudevigneUniversity Hospital Southampton NHS Foundation Trust; NIHR Southampton Biomedical Research Centre; University of Southampton
- Alexandra CobbUniversity College London
Abstract
Nitric oxide (NO) production plays a central role in conferring tolerance to hypoxia. Tibetan highlanders, successful high-altitude dwellers for millennia, have higher circulating nitrate and exhaled NO (ENO) levels than native lowlanders. Since nitrate itself can reduce the oxygen cost of exercise in normoxia it may confer additional benefits at high altitude. Xtreme Alps was a double-blinded randomised placebo-controlled trial to investigate how dietary nitrate supplementation affects physiological responses to hypoxia in 28 healthy adult volunteers resident at 4559 m for 1 week; 14 receiving a beetroot-based high-nitrate supplement and 14 receiving a low-nitrate 'placebo' of matching appearance/taste. ENO, vital signs and acute mountain sickness (AMS) severity were recorded at sea level (SL) and daily at altitude. Moreover, standard spirometric values were recorded, and saliva and exhaled breath condensate (EBC) collected. There was no significant difference in resting cardiorespiratory variables, peripheral oxygen saturation or AMS score with nitrate supplementation at SL or altitude. Median ENO levels increased from 1.5/3.0 mPa at SL, to 3.5/7.4 mPa after 5 days at altitude (D5) in the low and high-nitrate groups, respectively (p = 0.02). EBC nitrite also rose significantly with dietary nitrate (p = 0.004), 1.7-5.1 μM at SL and 1.6-6.3 μM at D5, and this rise appeared to be associated with increased levels of ENO. However, no significant changes occurred to levels of EBC nitrate or nitrosation products (RXNO). Median salivary nitrite/nitrate concentrations increased from 56.5/786 μM to 333/5,194 μM with nitrate supplementation at SL, and changed to 85.6/641 μM and 341/4,553 μM on D5. Salivary RXNO rose markedly with treatment at SL from 0.55 μM to 5.70 μM. At D5 placebo salivary RXNO had increased to 1.90 μM whilst treatment RXNO decreased to 3.26 μM. There was no association with changes in any observation variables or AMS score. In conclusion, dietary nitrate supplementation is well tolerated at altitude and significantly increases pulmonary NO availability and both salivary and EBC NO metabolite concentrations. Surprisingly, this is not associated with changes in hemodynamics, oxygen saturation or AMS development.
Abstract via Europe PMC. Copyright remains with the authors or publisher (CC BY).
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