Acute Nitrate Supplementation in Cyclists

Acute Nitrate Ingestion on Athletic Performance Clinical Trial

Official title:

Acute Dietary Nitrate Supplementation to Improve Performance in Endurance Trained Athletes

Clinical Trial Details — Status: Completed

Administrative data

• NCT number: NCT01384968
• Other study ID #: 11-3-033
• Status: Completed
• Phase: N/A
• First received: June 23, 2011
• Last updated: October 16, 2012
• Start date: July 2011
• Est. completion date: May 2012

Study information

• Verified date: October 2012
• Source: Maastricht University Medical Center
• Contact: n/a
• Is FDA regulated: No
• Health authority: Netherlands: The Central Committee on Research Involving Human Subjects (CCMO)
• Study type: Interventional

Clinical Trial Summary

Six days of dietary nitrate (NO3-) supplementation in the form of beetroot juice (~0.5 L•d-1; 5.1-11.2 mmol NO3- •d-1) has been purported to reduce pulmonary oxygen uptake (VO2) during submaximal exercise and increase tolerance to high-intensity workloads. These results suggest that dietary nitrate supplementation has the potential to act as an ergogenic aid. Recently, we assessed submaximal oxygen uptake and 10 km time trial performance after 6 d of dietary nitrate supplementation in trained cyclists. We demonstrated an improvement in time trial performance compared to the nitrate-depleted placebo. However, the minimal dosage and duration of nitrate supplementation that is needed to elicit these performance effects remain largely unknown. Therefore, the purpose of the study is to assess performance capacity following an acute dose of nitrate supplementation consumed 3 h prior to the onset of exercise in trained cyclists. We will test the hypothesis that a single dose (140 mL; ~8 mmol NO3-) of dietary nitrate supplementation in the form of beetroot juice, ingested 3 h prior to exercise will improve time trial performance in trained cyclists compared to a nitrate-depleted placebo.

Description:

Recent work in humans suggests that increasing nitric oxide (NO) bioavailability may induce physiological changes beyond the well known hemodynamic effects (Dejam, Hunter et al. 2004; Webb, Patel et al. 2008). NO plays a key role in the regulation of blood flow, muscle contractility, myocyte differentiation, glucose and calcium homeostasis (Dejam, Hunter et al. 2004). Within the human body, exogenous nitrate (NO3-) which has a half-life of 6-7 hours (h) (Lundberg, Weitzberg et al. 2008) is reduced to bioactive nitrite (NO2-) by facultative anaerobic bacteria in the saliva and further to NO via various pathways (Duncan, Dougall et al. 1995; Zhang, Naughton et al. 1998). Several groups (Larsen, Weitzberg et al. 2007; Bailey, Fulford et al. 2009; Bailey, Winyard et al. 2010; Larsen, Weitzberg et al. 2010; Vanhatalo, Bailey et al. 2010; Lansley, Winyard et al. 2011) have investigated whether dietary nitrate provision affects metabolic or circulatory parameters during exercise in vivo in humans. Oral ingestion of sodium nitrate (0.1 mmol•kg-1•d-1) for 2-3 days (d) has been shown to significantly reduce pulmonary oxygen uptake (VO2) during submaximal cycling exercise in both untrained (Larsen, Weitzberg et al. 2010) and trained men (Larsen, Weitzberg et al. 2007). Since the use of sodium nitrate is regulated in most countries, researchers have started to examine the impact of ingesting nitrate-rich foods, such as beetroot juice, on the physiological response to exercise (Bailey, Fulford et al. 2009; Bailey, Winyard et al. 2010; Vanhatalo, Bailey et al. 2010; Lansley, Winyard et al. 2011).

Recent work by Jones and colleagues have demonstrated that ingestion of 0.5 L beetroot juice per d for 6 d reduces pulmonary oxygen uptake during submaximal exercise (Bailey, Fulford et al. 2009; Vanhatalo, Bailey et al. 2010; Lansley, Winyard et al. 2011) and lowers the ATP cost of muscle force production suggesting an enhanced contractile efficiency (Bailey, Winyard et al. 2010). This improvement in exercise efficiency was evident acutely (2.5 h) after ingestion of a single 0.5 L bolus of beetroot and persisted for 15 d when supplementation was continued (Vanhatalo, Bailey et al. 2010). Although the active ingredient in beetroot has been assumed to be nitrate, beetroot is rich in several other potentially metabolically-active compounds (e.g. polyphenols). To confirm whether the proposed cardiovascular and physiological benefits of beetroot juice are solely attributable to its high NO3- content, Jones and colleagues tested beetroot juice against nitrate-depleted beetroot juice. They verified their previous findings (Bailey, Fulford et al. 2009) by demonstrating a lowered O2 cost of submaximal exercise following ingestion of 0.5 L beetroot juice for 6 d when compared with the nitrate-depleted juice (Lansley, Winyard et al. 2011).

From the proposed improvements in metabolic efficiency, it has been suggested that nitrate supplementation (0.5 L•d-1; ~5.1-11.2 mmol NO3- •d-1) may increase exercise tolerance or time to fatigue when exercise is performed at higher workloads (Bailey, Fulford et al. 2009; Bailey, Winyard et al. 2010; Vanhatalo, Bailey et al. 2010; Lansley, Winyard et al. 2011). The latter suggests that inorganic nitrate ingestion may act as a strong ergogenic aid. We recently tested the potential ergogenic properties of nitrate using a more practical, performance-based study that simulated athletic competition in a trained subject population (Cermak, Gibala et al. 2011). We demonstrated that following 6 d of dietary nitrate supplementation in the form of concentrated beetroot juice (140 mL•d-1; ~4 mmol NO3- •d-1), mean VO2 was lower during submaximal exercise and 10 km time-trial performance improved in trained cyclists (Cermak, Gibala et al. 2011). However, the minimal dosage and duration of nitrate supplementation that is needed to elicit these performance effects remains largely unknown. Although time to exhaustion is not a very practical performance measurement, improvements in such performance tests have been observed after only 4 d of dietary nitrate supplementation (0.5 L•d-1; ~6.2 mmol•d-1 NO3-). Furthermore, even a single dose of nitrate (~5.2 mmol NO3-) has been shown to lower mean VO2 values measured 2.5 h after ingesting 0.5 L of beetroot juice (Vanhatalo, Bailey et al. 2010). Whether a similar improvement in time-trial performance would also be observed after a shorter supplementation period is presently unknown. Therefore, the present study aims to investigate whether a single dose of dietary nitrate (140 mL; ~8 mmol NO3-) ingested 3 h prior to the onset of exercise will improve time-trial performance in trained cyclists.

Furthermore, inorganic nitrate ingestion (beetroot juice) has also been demonstrated to improve time to claudication pain while walking in peripheral artery disease patients (Kenjale, Ham et al. 2011), and lower plasma triglycerides in patients at risk for cardiovascular disease (Zand, Lanza et al. 2011), providing evidence for inorganic nitrate ingestion to improve vasodilation/perfusion. Whether a bolus ingestion of nitrate would also influence the perfusion of nutrients following the ingestion of a small meal remains unknown. Therefore, in a secondary aim, we want to investigate the plasma metabolite response in addition to nitrate and nitrite concentrations following the nitrate supplementation and subsequent meal ingestion.

1. OBJECTIVES The main objective will be to identify whether a bolus (140 mL) ingestion of dietary nitrate (~8 mmol NO3-) in the form of concentrated beetroot juice will acutely increase time-trial performance compared to a nitrate-depleted placebo (140 mL; ~0.0047 mmol NO3-). A secondary objective will be to measure blood samples after nitrate and meal ingestion to assess any changes in the concentration of nitrate, nitrite, glucose, insulin, lactate and free fatty acids. In this secondary objective, we are most interested in determining whether nitrate supplementation changes blood metabolites (glucose, insulin, lactate, free fatty acids) following 1) meal ingestion and 2) immediate post-exercise recovery period in comparison to the placebo. We will test the hypothesis that a single dose (140 mL; ~8 mmol NO3-) of dietary nitrate supplementation (beetroot juice) ingested 3 h prior to exercise will improve time-trial performance in trained cyclists compared to the nitrate-depleted placebo.

2. STUDY DESIGN (Protocol) After the assessment of aerobic capacity (step-wise exercise cycling test to exhaustion) and familiarization testing, subjects will be randomized in a double-blind fashion to the treatment order of a bolus ingestion of nitrate (beetroot juice) and placebo (nitrate-depleted beetroot juice). For the two experimental trials, subjects will report to the laboratory at 8.00 h for the insertion of the blood catheter into an antecubital vein. Subjects will then be asked to consume 140 mL of either concentrated beetroot juice nitrate or concentrated nitrate-depleted beetroot juice (placebo). Following the consumption of the beverage, subjects will be given a standardized breakfast and will then rest in the lab for 2.5 h before being weighed and fitted with a heart-rate monitor for the commencement of the time-trial (3 h post ingestion of treatment beverage). Blood samples will be drawn at time 0 min (before beverage ingestion), 30, 60, 90, 120, 150, 180 min (start of time-trial). Two more blood samples will be drawn immediately post and 30 minutes post time-trial (Figure 1). Sampling will occur every 30 minutes based on previous research examining blood metabolites following meal ingestion or an oral glucose load (van Dijk, Manders et al. 2011) and nitrate/nitrite concentrations (Webb, Patel et al. 2008). The last two blood samples will occur immediately following the time-trial and 30 min into the recovery period to assess any changes in metabolites and nitrate/nitrite concentrations from the exercise and during the short-term recovery period.

To assess time-trial performance, subjects will be instructed to perform a set amount of work in the shortest time possible. Total work to be performed will be calculated according to the equation of Jeukendrup, Saris, Brouns, and Kester (Jeukendrup, Saris et al. 1996), adapted by our lab (Beelen, Berghuis et al. 2009) :

Total amount of work = 0.60 • Wmax • 3,600

where Wmax is the maximal workload capacity determined during Visit 1 and 3,600 is the duration in seconds (equivalent to 1 hr). The ergometer will be set in linear mode to obtain 60% Wmax when subjects' cycle at their preferred cadence determined during Visit 1. The ergometer will be connected to a computer that will calculate and display the total amount of work performed. Subjects will receive no verbal or physiological feedback during the time-trial. The only information subjects will receive is the absolute amount of work performed and the percentage of total work performed relative to the set amount of work that needs to be completed. A fan will be placed 1 meter behind each participant to provide cooling and air circulation during the trials. Heart rate (Polar, Finland) will be recorded continuously throughout the test. This type of time-trial has been validated and used before in our lab (Beelen, Berghuis et al. 2009), for an overview of validation studies see (Currell and Jeukendrup 2008). Examples of coefficients of variation in similar trials are 1.1 (Palmer, Dennis et al. 1996), 0.7 (Smith, Davison et al. 2001) and 0.9 (Laursen, Shing et al. 2003). Water will be provided ad libitum during visits 1 and 2. However, the water consumed during visit 2 (familiarization trial) will be measured and repeated for visits 3 and 4 (exercise trials).

Recruitment information / eligibility

• Status: Completed
• Enrollment: 20
• Est. completion date: May 2012
• Est. primary completion date: January 2012
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: Male
• Age group: 18 Years to 30 Years

Eligibility

Inclusion Criteria:

• Healthy

• Male

• 18 - 30 years of age

• Endurance cycling trained (=3 sessions of endurance exercise per week)

• VO2 max = 50 ml/kg/min

• Training history of more than one year of =3 sessions of endurance cycling exercise per week

• BMI <25 kg/m2

Exclusion Criteria:

• Use of medication

• Smoking

• Currently supplementing diet with beetroot juice

Study Design

Allocation: Randomized, Intervention Model: Crossover Assignment, Masking: Double Blind (Subject, Investigator)

Related Conditions & MeSH terms

• Acute Nitrate Ingestion on Athletic Performance

Intervention

Dietary Supplement:
• beetroot juice
170 mL beetroot juice (Beet It, James White drinks Ltd).

Locations

Country	Name	City	State
Netherlands	Maastricht University	Maastricht	Limburg

Sponsors (1)

Lead Sponsor	Collaborator
Maastricht University Medical Center

Country where clinical trial is conducted

Netherlands, 

References & Publications (21)

Bailey SJ, Fulford J, Vanhatalo A, Winyard PG, Blackwell JR, DiMenna FJ, Wilkerson DP, Benjamin N, Jones AM. Dietary nitrate supplementation enhances muscle contractile efficiency during knee-extensor exercise in humans. J Appl Physiol (1985). 2010 Jul;109(1):135-48. doi: 10.1152/japplphysiol.00046.2010. Epub 2010 May 13. Erratum in: J Appl Physiol. 2010 Sep;109(3):943. — View Citation

Bailey SJ, Winyard P, Vanhatalo A, Blackwell JR, Dimenna FJ, Wilkerson DP, Tarr J, Benjamin N, Jones AM. Dietary nitrate supplementation reduces the O2 cost of low-intensity exercise and enhances tolerance to high-intensity exercise in humans. J Appl Physiol (1985). 2009 Oct;107(4):1144-55. doi: 10.1152/japplphysiol.00722.2009. Epub 2009 Aug 6. — View Citation

Beelen M, Berghuis J, Bonaparte B, Ballak SB, Jeukendrup AE, van Loon LJ. Carbohydrate mouth rinsing in the fed state: lack of enhancement of time-trial performance. Int J Sport Nutr Exerc Metab. 2009 Aug;19(4):400-9. — View Citation

Cermak NM, Gibala MJ, van Loon LJC. Nitrate supplementation improves 10 km time trial performance in trained cyclists. Medicine & Science in Sports & Exercise (under review), 2011.

Currell K, Jeukendrup AE. Validity, reliability and sensitivity of measures of sporting performance. Sports Med. 2008;38(4):297-316. Review. — View Citation

Dejam A, Hunter CJ, Schechter AN, Gladwin MT. Emerging role of nitrite in human biology. Blood Cells Mol Dis. 2004 May-Jun;32(3):423-9. Review. — View Citation

Duncan C, Dougall H, Johnston P, Green S, Brogan R, Leifert C, Smith L, Golden M, Benjamin N. Chemical generation of nitric oxide in the mouth from the enterosalivary circulation of dietary nitrate. Nat Med. 1995 Jun;1(6):546-51. — View Citation

Jeukendrup A, Saris WH, Brouns F, Kester AD. A new validated endurance performance test. Med Sci Sports Exerc. 1996 Feb;28(2):266-70. — View Citation

Kenjale AA, Ham KL, Stabler T, Robbins JL, Johnson JL, Vanbruggen M, Privette G, Yim E, Kraus WE, Allen JD. Dietary nitrate supplementation enhances exercise performance in peripheral arterial disease. J Appl Physiol (1985). 2011 Jun;110(6):1582-91. doi: 10.1152/japplphysiol.00071.2011. Epub 2011 Mar 31. — View Citation

Lansley KE, Winyard PG, Fulford J, Vanhatalo A, Bailey SJ, Blackwell JR, DiMenna FJ, Gilchrist M, Benjamin N, Jones AM. Dietary nitrate supplementation reduces the O2 cost of walking and running: a placebo-controlled study. J Appl Physiol (1985). 2011 Mar;110(3):591-600. doi: 10.1152/japplphysiol.01070.2010. Epub 2010 Nov 11. — View Citation

Larsen FJ, Weitzberg E, Lundberg JO, Ekblom B. Dietary nitrate reduces maximal oxygen consumption while maintaining work performance in maximal exercise. Free Radic Biol Med. 2010 Jan 15;48(2):342-7. doi: 10.1016/j.freeradbiomed.2009.11.006. Epub 2009 Nov 12. — View Citation

Larsen FJ, Weitzberg E, Lundberg JO, Ekblom B. Effects of dietary nitrate on oxygen cost during exercise. Acta Physiol (Oxf). 2007 Sep;191(1):59-66. Epub 2007 Jul 17. — View Citation

Laursen PB, Shing CM, Jenkins DG. Reproducibility of a laboratory-based 40-km cycle time-trial on a stationary wind-trainer in highly trained cyclists. Int J Sports Med. 2003 Oct;24(7):481-5. — View Citation

Lundberg JO, Weitzberg E, Gladwin MT. The nitrate-nitrite-nitric oxide pathway in physiology and therapeutics. Nat Rev Drug Discov. 2008 Feb;7(2):156-67. doi: 10.1038/nrd2466. Review. — View Citation

Palmer GS, Dennis SC, Noakes TD, Hawley JA. Assessment of the reproducibility of performance testing on an air-braked cycle ergometer. Int J Sports Med. 1996 May;17(4):293-8. — View Citation

Smith MF, Davison RC, Balmer J, Bird SR. Reliability of mean power recorded during indoor and outdoor self-paced 40 km cycling time-trials. Int J Sports Med. 2001 May;22(4):270-4. — View Citation

van Dijk JW, Manders RJ, Hartgens F, Stehouwer CD, Praet SF, van Loon LJ. Postprandial hyperglycemia is highly prevalent throughout the day in type 2 diabetes patients. Diabetes Res Clin Pract. 2011 Jul;93(1):31-7. doi: 10.1016/j.diabres.2011.03.021. Epub 2011 Apr 16. — View Citation

Vanhatalo A, Bailey SJ, Blackwell JR, DiMenna FJ, Pavey TG, Wilkerson DP, Benjamin N, Winyard PG, Jones AM. Acute and chronic effects of dietary nitrate supplementation on blood pressure and the physiological responses to moderate-intensity and incremental exercise. Am J Physiol Regul Integr Comp Physiol. 2010 Oct;299(4):R1121-31. doi: 10.1152/ajpregu.00206.2010. Epub 2010 Aug 11. — View Citation

Webb AJ, Patel N, Loukogeorgakis S, Okorie M, Aboud Z, Misra S, Rashid R, Miall P, Deanfield J, Benjamin N, MacAllister R, Hobbs AJ, Ahluwalia A. Acute blood pressure lowering, vasoprotective, and antiplatelet properties of dietary nitrate via bioconversion to nitrite. Hypertension. 2008 Mar;51(3):784-90. doi: 10.1161/HYPERTENSIONAHA.107.103523. Epub 2008 Feb 4. — View Citation

Zand J, Lanza F, Garg HK, Bryan NS. All-natural nitrite and nitrate containing dietary supplement promotes nitric oxide production and reduces triglycerides in humans. Nutr Res. 2011 Apr;31(4):262-9. doi: 10.1016/j.nutres.2011.03.008. — View Citation

Zhang Z, Naughton D, Winyard PG, Benjamin N, Blake DR, Symons MC. Generation of nitric oxide by a nitrite reductase activity of xanthine oxidase: a potential pathway for nitric oxide formation in the absence of nitric oxide synthase activity. Biochem Biophys Res Commun. 1998 Aug 28;249(3):767-72. Erratum in: Biochem Biophys Res Commun 1998 Oct 20;251(2):667. — View Citation

* Note: There are 21 references in all — Click here to view all references

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Time-trial performance	Subjects will be asked to visit the laboratory for a total of 4 visits over 4 weeks. During visits 2,3 and 4 time-trial performance will be assessed. Each visit will be separated on average by at least 1 week. Therefore, if subjects have their first visit (max text) in week 1, their time trial performance will be assessed during weeks 2, 3 and 4.	Laboratory visits 2, 3 and 4 (each visit separated by ~ 1wk))	No
Secondary	Nitrate and nitrite plasma concentration	During visits 3 and 4 (during the 4 week study), subjects will undergo blood sampling whereby we will assess plasma concentration for nitrate and nitrite. Each visit will be separated by approximately 1 week. Therefore, if subjects enroll in the study during week 1, we will assess nitrate and nitrite during weeks 3 and 4.	Laboratory visits 3 and 4 (approximately 1 wk apart)	No
Secondary	blood metabolites (glucose, insulin, lactate, free fatty acids)	During visits 3 and 4, subjects will undergo blood sampling whereby we will assess plasma concentration for blood metabolites (glucose, insulin, lactate and free fatty acids). Each visit will be separated by approximately 1 week. Therefore, if subjects enroll in the study during week 1, we will assess blood metabolites during weeks 3 and 4.	Laboratory visits 3 and 4 (approximately 1 wk apart)	No