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The Effects of Vitamin D Supplementation on Aerobic Fitness in Athletes (VDAF)

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT02278172
Recruitment Status : Completed
First Posted : October 29, 2014
Last Update Posted : May 25, 2016
Northern Ireland Executive
Information provided by (Responsible Party):
Dr Pamela Magee, University of Ulster

Brief Summary:

The primary aim of the study is to identify if vitamin D3 supplementation influences VO2max in athletes.

Secondary aims are to determine if vitamin D3 supplementation impacts on measures of muscle function, lung function, body composition, immune function and the self-reported incidence of upper respiratory tract infection.

This double-blind, randomised, placebo-controlled trial is of parallel design and will aim to recruit a total of 50 athletes randomised into either a placebo or treatment group for a 12-week intervention.

Condition or disease Intervention/treatment Phase
Aerobic Fitness (VO2max) Dietary Supplement: Vitamin D Dietary Supplement: Placebo Phase 4

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Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 44 participants
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary Purpose: Basic Science
Official Title: The Effects of Vitamin D Supplementation on VO2max in Athletes: a Randomised, Double-blind, Placebo-controlled Trial
Study Start Date : October 2014
Actual Primary Completion Date : April 2015
Actual Study Completion Date : April 2015

Resource links provided by the National Library of Medicine

MedlinePlus related topics: Vitamin D
Drug Information available for: Vitamin D

Arm Intervention/treatment
Active Comparator: Vitamin D3 3000IU (75μg)
Treatment solution delivered via oral spray once daily for 12-weeks
Dietary Supplement: Vitamin D
3000IU (75 μg) vitamin D in a commercially available oral spray solution
Other Names:
  • cholecalciferol
  • vitamin D3

Placebo Comparator: Placebo
Placebo solution delivered via oral spray once daily for 12-weeks
Dietary Supplement: Placebo
Placebo oral spray solution manufactured to mimic the vitamin D oral spray

Primary Outcome Measures :
  1. Aerobic fitness (VO2max) [ Time Frame: At baseline and at 12-weeks ]

    A medical screening questionnaire will be completed prior to the test. Athletes resting blood pressure will be measured twice to rule out resting hypertension. After a standardised warm-up, starting speed will be 8/km/hr at 1% incline, until 17/km/hr, after which incline will increase by 1% every minute until VO2max is met. A metabolic cart (Metalyzer 3B) will measure the athlete's ventilation (oxygen uptake and carbon dioxide output) throughout the test.

    The test will be terminated when two of the following criterion are met*:

    Respiratory exchange ratio reaches/exceeds 1.15 AND VO2 plateau observed OR Heart rate within 10bpm of age-predicted maximum

    * Except when volitional exhaustion occurs Athletes will be asked to refrain from strenuous activity for 24 hours prior to VO2max testing in order to control for last bout effects.

    Post-exercise lactate concentration (age and gender adjusted) will further-verify that VO2max was attained using a Lactate Pro device.

Secondary Outcome Measures :
  1. Hand grip strength [ Time Frame: At baseline and at 12-weeks ]
    Hand grip dynamometry will be used to assess athletes grip strength. This will be measured on both dominant and non-dominant hands three times. The athlete will be asked to hold the device and grip as tightly as possible whilst holding the device alongside their body. There will be a 10 second rest period between measurements.

  2. Vertical jump height [ Time Frame: At baseline and at 12-weeks ]
    Athletes will be asked to reach upwards as far as possible, from a standing position and mark this point on a wall. After this they will be asked to perform a counter-movement jump a total of 3 times with a 10 second rest-period between jumps, reaching as high as possible and making a mark each time. Vertical jump height is calculated from the difference between standing reach height and the best height reached when performing a counter-movement jump.

  3. Lung function [ Time Frame: At baseline and at 12-weeks ]

    Forced expiratory volume at 1 second (FEV1) and forced vital capacity (FVC) will be measured. A calibrated Carefusion® MicroLab portable spirometer will be used to measure these variables.The athletes will need to take a maximal inhalation and then perform a full exhalation as fast as possible into a disposable mouthpiece.

    This procedure will be repeated three times and an average taken at each time-point. The timing of repeats will be at the athletes discretion.

  4. Nutrient intake [ Time Frame: At baseline only/ at baseline and at 12-weeks ]

    Dietary vitamin D and calcium intake will be estimated using a validated food frequency questionnaire at one time point (baseline only). This is due to studies highlighting equivocal variation in dietary vitamin D intake throughout the year.

    24hr recalls will be completed at baseline and at 12-weeks in order to derive mean nutrient intakes for the vitamin D and placebo treatment groups respectively.

  5. Self-reported upper respiratory illness [ Time Frame: Once per week up to week 12 ]
    An online questionnaire will allow athletes to record if they have any symptoms that are associated with upper respiratory infections. The athlete will be asked to mark a series of boxes to indicate how many symptom(s) if any that they have had each week.

  6. Physical activity levels [ Time Frame: At baseline and at 12-weeks ]
    The 'Modified Recent Physical Activity Questionnaire' produced by the Medical Research Council (a validated physical activity questionnaire) will be completed on two occasions to estimate physical activity levels.

  7. Body composition [ Time Frame: At baseline and at 12-weeks ]
    Body composition will be measured using the BodPod, employing air plethysmography (displacement of air) to accurately measure percentage fat mass and percentage fat-free mass.

  8. Vitamin D status [ Time Frame: At baseline and at 12-weeks ]
    25-hydroxyvitamin D (25(OH)D) will be quantified, in serum, using liquid chromatography-tandem mass spectrometry (LCMS/MS). Other biomarkers of vitamin D metabolism (adjusted calcium and parathyroid hormone) will be quantified using a clinical chemistry analyser and commercially available enzyme-linked immunosorbent assay.

  9. Immune function [ Time Frame: At baseline and at 12-weeks ]
    A range of immune markers such as interleukin-6, cathelicidin (LL-37) and C-reactive protein will be measured using a commercially available multiplex immunoassay.

Information from the National Library of Medicine

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Ages Eligible for Study:   18 Years and older   (Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • Athletes whose sport does not primarily consist of an anaerobic component
  • Apparently healthy
  • Over the age of 18

Exclusion Criteria:

  • Resting arterial hypertension
  • Individuals who are not an athlete at a University/local sports team
  • Athletes who predominantly utilise anaerobic energy systems
  • Athletes under the age of 18
  • Those that have consumed a supplement containing vitamin D (greater than 400IU/day) or iron supplements for up to 30 days prior to starting the study
  • Those with health conditions identified by the screening questionnaire
  • Individuals that are on prescribed medication that is known to affect vitamin D metabolism
  • Those following a vegan diet
  • Those with a physical disability that would prevent successful completion of the exercise test
  • Those who have either had a sun holiday in the 4 weeks prior to starting the study
  • Those planning a sun holiday during the intervention period

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT02278172

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United Kingdom
Human Intervention Studies Unit (HISU), University of Ulster
Coleraine, Londonderry, United Kingdom, BT52 1SA
Sponsors and Collaborators
University of Ulster
Northern Ireland Executive
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Principal Investigator: Pamela J Magee, PhD University of Ulster
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Responsible Party: Dr Pamela Magee, University of Ulster Identifier: NCT02278172    
Other Study ID Numbers: REC14.0087
First Posted: October 29, 2014    Key Record Dates
Last Update Posted: May 25, 2016
Last Verified: May 2016
Keywords provided by Dr Pamela Magee, University of Ulster:
vitamin D
Additional relevant MeSH terms:
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Vitamin D
Growth Substances
Physiological Effects of Drugs
Bone Density Conservation Agents
Calcium-Regulating Hormones and Agents