Acute Nitrate Supplementation in Cyclists

October 16, 2012 updated by: Maastricht University Medical Center

Acute Dietary Nitrate Supplementation to Improve Performance in Endurance Trained Athletes

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.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed 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).

Study Type

Interventional

Enrollment (Actual)

20

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Netherlands
    • Limburg
      • Maastricht, Limburg, Netherlands, 6229ER
        • Maastricht University

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

16 years to 28 years (Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

Male

Description

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 Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Allocation: Randomized
  • Interventional Model: Crossover Assignment
  • Masking: Double

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Beetroot juice
beetroot juice (170 mL, 8 mmol nitrate)
Dietary supplement: beetroot juice
170 mL beetroot juice (Beet It, James White drinks Ltd).
Other Names:
  • Beet It, James White Drinks Ltd.
Placebo Comparator: Nitrate-depleted beetroot juice
140 mL ...0 nitrate. Beetroot juice
Dietary supplement: beetroot juice
170 mL beetroot juice (Beet It, James White drinks Ltd).
Other Names:
  • Beet It, James White Drinks Ltd.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Time-trial performance
Time Frame: Laboratory visits 2, 3 and 4 (each visit separated by ~ 1wk))
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))

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Nitrate and nitrite plasma concentration
Time Frame: Laboratory visits 3 and 4 (approximately 1 wk apart)
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)
blood metabolites (glucose, insulin, lactate, free fatty acids)
Time Frame: Laboratory visits 3 and 4 (approximately 1 wk apart)
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)

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Maastricht University Medical Center

Investigators

  • Study Director: Luc van Loon, Ph.D., Maastricht University
  • Principal Investigator: Naomi Cermak, Ph.D., Maastricht University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start

July 1, 2011

Primary Completion (Actual)

January 1, 2012

Study Completion (Actual)

May 1, 2012

Study Registration Dates

First Submitted

June 23, 2011

First Submitted That Met QC Criteria

June 28, 2011

First Posted (Estimate)

June 29, 2011

Study Record Updates

Last Update Posted (Estimate)

October 17, 2012

Last Update Submitted That Met QC Criteria

October 16, 2012

Last Verified

October 1, 2012

More Information

Terms related to this study

Keywords

Other Study ID Numbers

  • 11-3-033

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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