HTN: Vitamins (2015)


Wamberg L, Kampmann U, Stodkilde-Jorgensen H, Rejnmark L, Pedersen SB, Richelsen B. Effects of vitamin D supplementation on body fat accumulation, inflammation, and metabolic risk factors in obese adults with low vitamin D levels: Results from a randomized trial. Eur J Intern Med. 2013; 24: 644-649.

PubMed ID: 23566943
Study Design:
Randomized Controlled Trial
A - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
To determine the effect of vitamin D supplementation in obese adults with low plasma levels of 25OH-D on liver fat content and obesity-related conditions including hypertension, dyslipidemia, inflammation and insulin resistance.
Inclusion Criteria:
  • Age less than 18 years
  • BMI 30kg/m2 or more
  • Plasma vitamin D levels less than 50nmol per L (less than 20ng per ml)
  • Informed consent.
Exclusion Criteria:
  • Weight more than 125kg
  • History of diabetes
  • History of sarcoidosis
  • History of nephrolithiasis
  • History of osteomalacia
  • History of alcohol or substance abuse
  • Fasting plasma glucose higher than 7mmol per L (higher than 126mg per dL)
  • Hypercalcemia
  • Impaired renal function (plasma creatinine higher than 130mcgmol per L
  • Impaired hepatic function (alanine aminotransferase higher than 135 IU)
  • Recent weight change of ±3kg
  • Vitamin D treatment within the past three months.
Description of Study Protocol:


Newspaper announcements.


Randomized controlled trial:

  • Randomized to vitamin D supplementation or placebo by hospital pharmacy:
    • Computer-generated randomization code
    • Block randomization procedure used with strata (gender, fasting glucose).

Blinding Used

Placebo was similar in appearance to vitamin D supplement.


  • 7,000 IU cholecalciferol (175mcg, 35mcg each x five pills) vs. placebo (five pills) for 26 weeks
  • Usual diet and physical activity.

Statistical Analysis

  • Modified intention to treat approach, including all included subjects who completed the trial
  • Two sample T-test or Mann-Whitney U-test: Evaluate changes between groups
  • Paired T-test: Evaluate changes within groups
  • Pearson's correlation
  • Sample size calculation suggested that 26 participants were required in each group
  • Participants stratified by gender and fasting blood glucose (6.1mmol per L, 110mg per dL)
  • Statistical significance: P<0.05.
Data Collection Summary:

Timing of Measurements

  Baseline Week 2 Week 10 Week 18
Clinical exam x      
Anthropometrics x      
Physical activity assessment x      
Blood pressure x     x
Blood sampling x     x
Three-day food record   x    
Body composition x     x
Safety assessment   x x x
Adverse events   x x x
Compliance assessment   x x x

Dependent Variables

  • Primary: Decrease in high-sensitive C-reactive protein (hsCRP)
  • Secondary:
    • Total fat mass (% total fat, DXA)
    • Total lean body mass (DXA)
    • Abdominal and visceral adipose tissue (MRI imaging)
    • Intrahepatic and intramyocellular lipids (1H-MR spectroscopy)
    • Plasma cholesterol and triglycerides
    • Plasma 25OHD levels (isotope dilution liquid chromatography-tandem mass spectrometry)
    • Plasma glucose, insulin, hsCRP, IL-6, MCP-1, adiponectin, leptin, MMP-9, PAI-1, osteopontin (commercial kits)
    • Insulin resistance (HOMA-IR).

Independent Variables

Vitamin D supplementation vs. placebo.


Description of Actual Data Sample:

Initial N

N=52 (15 males and 37 females):

  • Vitamin D supplement: N=26 (8 males and 18 females)
  • Placebo: N=26 (seven males and 9 females).

Attrition (final N)


  • Vitamin D supplement: N=22:
    • Withdrew consent, personal reasons: N=2
    • Dropped out: N=2.
  • Placebo: N=21:
    • Withdrew consent, personal reasons: N=3
    • Pregnancy: N=1
    • Dropped out: N=1.


 Range of 18 years to 50 years (mean±SD):

  • Vitamin D supplement: 39.5±8.0 years
  • Placebo: 41.2±6.8 years.

Other Relevant Demographics

No differences between groups at baseline for the following: fasting blood glucose, plasma PTH, smoking history and physical activity levels.

  • Plasma 25OH-D (nmol per L), mean±SD:
    • Vitamin D supplement: 34.5±10.8
    • Placebo: 34.6±10.3.
  • Dietary vitamin D (mcg per day), median (25%; 75%):
    • Vitamin D supplement: 2.1 (1.5; 4.0)
    • Placebo: 1.7 (1.4; 3.1).
  • Dietary calcium (mg per day), mean±SD:
    • Vitamin D supplement: 992±400
    • Placebo: 936±389.


  • BMI (mean±SD):
    • Vitamin D supplement: 36.1±3.4
    • Placebo: 35.0±3.2.
  • Blood pressure (SBP and DBP), mean±SD:
    • Vitamin D supplement: 133±17 and 84.1±10
    • Placebo: 132±10 and 82±10.


Aarhus University, Aarhus University Hospital; Aarhus, Denmark.


Summary of Results:

Key Findings

  • Primary outcome: No significant changes were observed within and between groups from baseline to end of study for hsCRP.
  • Secondary outcomes:
    • Significant differences in plasma 25OH-D levels were noted within groups at end of study:
      • Within group differences: Baseline; end of study (mean±SD)
        • Vitamin D supplement: 33.0±10.8; 110.2±21.2, P<0.001
        • Placebo: 34.0±9.0; 46.8±17.3, P<0.001.
      • Significant between group differences were observed at the end of study (P<0.001).
    • No significant changes were noted within and between groups at the end of study for blood pressure and other metabolic and inflammatory markers
    • No significant differences were observed within and between groups at the end of study for body composition measures and liver fat content
    • At baseline intra-hepatic lipid content and visceral adipose tissue was inversely related to 25OH-D levels (R=–0.37, P=0.008 and R=–0.33, P=0.02, respectively)
    • At baseline intra-hepatic lipid content was positively related to plasma insulin (R= 0.30, P=0.04), intra-myocellular lipids (R=0.37, P=0.01) and visceral adipose tissue (R=0.52, P<0.0001).

Other Findings

  • Compliance:
    • Overall compliance was more than 80% for all subjects
    • Vitamin D supplement (mean±SD): 95±6%
    • Placebo (mean±SD)94±8%.
  • No significant differences in adverse events were reported between groups. Side effects included constipation, nausea, headaches and tiredness. Symptomatic hypercalcemia was not noted among participants during the study.
  • Three participants were using hypertensive medications and one was using lipid-lowering medications; no changes in dosages occurred during the study.
Author Conclusion:
Cholecalciferol supplementation in obese adults with low vitamin D status for 26 weeks had no effect on blood pressure, metabolic or inflammatory markers, body composition indices or liver fat accumulation.
Funding Source:
Pharmaceutical/Dietary Supplement Company:
University/Hospital: Aarhus University, Aarhus University Hospital; Aarhus, Denmark
Reviewer Comments:
  • Seventeen percent of the participants dropped out resulting in a loss of power
  • Small number of males
  • Women were pre-menopausal or peri-menopausal
  • No one was receiving hormone therapy
  • Short intervention period
  • Increase in plasma vitamin D levels in the placebo group attributed to seasonal variation
  • Exclusion criteria did not mention anything about vitamin supplements or conditions and medications affecting the absorption of calcium and vitamin D
  • Not intention to treat; used modified intention to treat
  • The hypothesis listed in the article indicated that higher plasma 25OH-D levels would decrease liver fat content, which would result in improved obesity-related complications such as inflammation, insulin resistance, dyslipidemia and hypertension and chose hsCRP as the outcome variable. In the discussion the authors focused on secondary outcome variables and did not address hsCRP or inflammation. This brings up the question of why hsCRP was chosen as the primary outcome variable.
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? Yes
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? Yes
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? ???
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? ???
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? ???
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? ???
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? No
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? ???
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? Yes
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes