Effect of Vitamin D3 Supplementation on Cardiometabolic Risk
Condition: Cardiovascular Disease; Diabetes; Bone Disease
MeSH terms: Bone Diseases; Cardiovascular Diseases
Study type: Interventional

Summary: 
      Supplementation studies with vitamin D have been performed where cardiometabolic risk markers
      have been assessed but these are few, and results are inconsistent. Hence, the purpose of
      this study is to determine:

        1. Whether administering supplemental Vitamin D3 at a dose of 5000IU/day (125µg) in
           overweight and obese adult participants for 8 weeks will significantly increase
           circulating concentrations of 25(OH)D or achieve optimal vitamin D status.

        2. Whether administering supplemental Vitamin D3 at a dose of 5000IU/day (125µg) in
           overweight and obese participants for 8 weeks will significantly improve the
           cardiometabolic parameters measured.

        3. To evaluate the relationship between these variables and 25(OH)D concentration. We
           hypothesise that there will be a significant increase in plasma 25(OH)D following 8
           weeks (56days) supplementation of oral vitamin D3 at a dose of 5000IU/day (125µg);
           Administering supplemental Vitamin D3 at a dose of 5000IU/day (125µg) in overweight and
           obese participants for 8 weeks will significantly improve the cardio metabolic
           parameters measured, and there will be a relationship between these variables and
           25(OH)D concentrations.
    

Detailed description: 
      This study is a parallel randomised, double-blind placebo - controlled trial which will be
      conducted at the University of Chester, Chester, United Kingdom. Ethical permission has been
      obtained through the University of Chester Faculty Research Ethics Committee(855/13/AT/CSN).
      Participants, especially students/staff will be recruited from the University of Chester by
      email, posters/leaflets.

      Males were chosen for this study due to their higher risk of developing cardiometabolic
      diseases compared to premenopausal women. The participants will be randomised to receive
      either a vitamin D supplement (5000IU (125µg)/d) or placebo for eight weeks. A computer
      generated random number sequence will be used to assign participants to the intervention and
      placebo group. Eligibility will be based on 25(OH)D assessment made at a screening visit
      before the baseline visit, and participants with plasma 25(OH)D level ≤ 75nmol/l will be
      invited to participate in the study. To ensure compliance with the intervention, participants
      will be sent reminders about the intervention appointments by email or phone calls. The study
      will be performed according to the declaration of Helsinki. All participants will provide
      written consent. Study participants will be instructed to store the study supplements at room
      temperature. All unconsumed supplements will be returned and counted to assess compliance.

      MEASUREMENTS Dietary intake will be estimated at baseline and post intervention using a three
      day food diary and information about health conditions, medications and health related
      behaviors will be assessed by a pre-screen test questionnaire, physical activity will be
      evaluated as the average of the metabolic equivalent of task (MET-min/week) using the
      International Physical Activity Questionnaire. Participants will be assessed at baseline (day
      0), days 28 and 56. The plasma samples will be batch analyzed at the end of the trial.

      ANTHROPOMETRIC MEASUREMENTS Height (m2) will be measured without shoes at baseline, using a
      stadiometer to the nearest 0.1cm precision, Body weight (kg) will be measured without shoes
      at baseline through post intervention using a digital scale with participants wearing light
      indoor clothing, BMI will be calculated as weight in kilograms divided by the square of
      height in meters (kg/m2), and waist circumference at the iliac crest will be measured with a
      tape measure with the subject standing.

      PULSEWAVE VELOCITY AND BLOOD PRESSURE MEASUREMENTS Participants will be given a glass of
      water and allowed to rest for 5 minutes in a supine position and afterwards the pulse wave
      velocity meter (Arteriograph) cuff, for measuring arterial stiffness and blood pressure will
      be placed tightly round the dominant arm. Overall, three measurements will be performed but
      only the mean of two measurements will be taken.

      BIOCHEMICAL MEASUREMENTS A morning blood sample will be collected by venepuncture from the
      antecubital vein according to standard protocols, with participants in a sitting position
      after an overnight fast of at least 8 hours. Blood samples will be drawn into 10ml lithium
      heparin and ethylene diamine triacetic acid (EDTA) tubes to avoid clotting after which they
      will be immediately transferred into an ice box and then centrifuged for 10 minutes at four
      degrees Celsius at 3500rpm. Afterwards the centrifuged plasma will be transferred into
      aliquots and stored at -80 degrees Celsius until analyzed.

      CONDUCT OF THE STUDY

      This study will require the participants to attend four clinic sessions on four separate
      days.

      Clinic 1(day 0): Participants are expected to complete a consent form and screening test
      questionnaire after which their weight, height and waist circumference are to be measured.
      Afterwards, approximately 0.5ml of blood will be collected by finger prick and put in a
      heparin tube to avoid clotting for vitamin D status screening to ascertain if participant is
      eligible to partake in the study. Eligible participants will be invited to take part in the
      study.

      Clinic 2 (week 0): Weight, height, waist circumference and blood pressure and body fat
      measurements will be performed. Afterwards, 25ml of blood will be collected to assess the
      cardiometabolic risk markers. Participants will then be randomised to receive either vitamin
      D or placebo (without the active ingredient) supplements for the intervention period.

      Clinic 3 (week 4): The procedure performed in clinic 2 will be repeated in this clinic.

      Clinic 4 (Week 8): The procedure performed in clinic 2 will be repeated. It is anticipated
      that the maximum length of each clinic visit will be 45mins.

      Participants will be expected to complete a three-day food diary and physical activity
      questionnaire at Clinic 2 and 4.

      SAMPLE-SIZE ESTIMATION

      The estimated sample size will be 58 (29 per group), this sample size will allow for the
      detection of a treatment difference at 95% power, 0.97 effect size and 5% significance. The
      power calculation was based on a study by (Witham et al., 2012), and the primary outcome flow
      mediated dilation (FMD) a parameter of endothelial function from which an estimate of 29 per
      group was obtained, to allow for loss to follow up, sample size was increased to 37 (25%) per
      group (n= 74). Sample size estimation was conducted using G. Power version 3.1 software.

      DATA-ANALYSIS

      Data will be checked for a normal distribution by using Shapiro-Wilk since n = 74, and a
      homogenous variance will be assessed by Levene's statistic. if assumptions of a normal
      distribution and homogenous variance have been met , a parametric approach will be adopted,if
      not, a non parametric approach will be adopted

      To assess the difference between the groups and the repeated measurement, i will perform a
      Mixed Model Anova,and any difference observed will be further analysed by a post- hoc, Tukey
      test.

      To check for a relationship between variables and 25(OH)D, Pearson's correlation will be
      conducted if assumptions were met or spearman's correlation if assumptions were not met .

      Descriptive statistics will be consulted to determine where findings differ from baseline
      values.The mean and standard deviation will provide information about changes that will
      occur.
    

Intervention name(s): Vitamin D3; Placebo
Intervention type(s): Dietary Supplement; Other
Intervention description(s): 5000IU (125mcg) vitamin D3 tablet daily over 8 weeks (56 days).; 100% Lactose tablet daily over 8 weeks (56 days).
Other intervention name(s): Cholecalciferol; Non-active ingredient
Intervention MeSH terms: Vitamin D; Cholecalciferol
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Prevention
Keywords: Vitamin D; Cardiovascular disease; Diabetes; Obesity; Cardiometabolic; Bone disease