Cardiovascular Disease and Micronutrients

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To determine the effect of vitamin E on fasting blood sugar, serum insulin and glycated hemoglobin in patients with Type II non-insulin dependent diabetes.

Inclusion Criteria:
  • Aged 20 to 60 years
  • Non-smokers
  • Normal serum lipid levels
  • Normal blood pressure
  • Type II diabetes
  • Only drugs equal to oral hypoglycemic agents
  • Provided informed consent.
Exclusion Criteria:
  • Less than 18 years of age or greater than 60 years
  • Smokers
  • Complications related to diabetes
  • Elevated serum lipids
  • Elevated blood pressure
  • Type I diabetes
  • Taking medications other than oral hypoglycemic agents.
Description of Study Protocol:
  • Recruitment: Recruited from the Isfahan Social Security Service Clinic
  • Design: Randomized controlled trial
  • Blinding used: Placebo for vitamin E.

Intervention

  •  Participants randomized to one of two groups:
    • 200 IU vitamin E daily
    • Placebo.
  • Duration of the study was 27 weeks
  • Study medication taken one hour before breakfast, two hours after breakfast or four hours after lunch.

Statistical Analysis

  • Paired T-test was used to compare treatment effects within each group
  • Independent T-test was used to compare changes between the vitamin E and placebo groups
  • ANOVA was used to compared means of independent variables.
Data Collection Summary:

Timing of Measurements

 
Baseline
Three Weeks
Six Weeks
10 Weeks

14
W
eeks

18
Weeks
22
Weeks
27
Weeks
Fasting Blood Sugar
X
X
X
X
X
X
X
X
Glycated Hemoglobin
X
X
X
X
X
X
X
X
Serum Iinsulin
X
X
X
X
X
X
X
X
Vitamin E
X
 
 
 
 
 
 
X
Total Cholesterol
X
 
 
 
 
 
 
X
Triglycerides
X
 
 
 
 
 
 
X

Dependent Variables

  • Fasting blood sugar
  • Glycated hemoglobin
  • Serum insulin
  • Serum lipids
    • Total cholesterol
    • Triglycerides.
  • Vitamin E.

Independent Variables

  • 200 IU vitamin E
  • Placebo.
Description of Actual Data Sample:

Initial N

 N=100

  • Placebo: N=50
  • Vitamin E: N=50.

Attrition (Final N)

N=92 (excluded for lack of full participation)

  • Placebo: N=45
  • Vitamin E: N=47.

Age (Mean ±SD)

  • Placebo: 54.5±7.3 years
  • Vitamin E: 52.8±8.8 years.

Ethnicity

Not described.

Other Relevant Demographics

  • Duration of diabetes (months, mean ±SD)
    • Placebo: 59.±28.2
    • Vitamin E: 68.4±53.0
    • P=0.000.
  • Dose of glibenclamide (oral hypoglycemic agent, mean ±SD)
    • Placebo: 13.7±8.2mg per day
    • Vitamin E: 9.4±7.0mg per day
    • P=0.03.
  • Groups similar relative to sex, religion, marital status, education, occupation and dietary pattern.

Anthropometrics

  • BMI (mean ±SD)
    • Placebo: 24.2±3.6kg/m2
    • Vitamin E: 25.0±3.6kg/m2.

Location

Iran.

Summary of Results:

 Comparison of Baseline and End of Treatment (Mean ±SD)

Variables Placebo Group Vitamin E Group Statistical Significance of Group Difference
Baseline End Baseline End

Fasting Blood Sugar (mg/dL)

193.0±84.0
166.0±35.9
196.3±51.9

187.8±61.4

Not significant
Serum Insulin (IU/mL)
11.9±6.6

 

14.0±9
14.6±10.6

17.1±5.7

Not significant

Glycated Hemoglobin (Percentage)

9.7±1.6

 

9.8±1.6
10.1±1.2

9.7±1.6

Not significant
Total cholesterol (mg/dL)

161.7±41.9

 

174.7±70.7
156.2±36.9

159.1±50.4

Not significant
Triglycerides (mg/dL)

185.3±17.5

 

199.3±40.3
180.2±18.07

95.9±41.3

Not significant
Vitamin E (μmol/L)

10.8±3.0

 

10.0±2.9
10.2±3.6

16.5±2.8

Not significant

No significant within-group differences for any parameter except for the vitamin E level in the vitamin E supplemented group.

 

Author Conclusion:

Vitamin E supplementation had no effect on fasting blood sugar, glycated hemoglobin, insulin or lipid levels in people with Type II diabetes without complications.

Funding Source:
Government: Academy of Medical Science of Iran
Reviewer Comments:
  • Number of male and female participants in the study not described
  • Compliance with study medication not described
  • In terms of excluding participants, authors could have described the phrase "lack of full participation" better. It is uncertain whether the participants did not take the study medications as directed or were lost to follow-up.
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) No
  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? No
  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? ???
  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? Yes
  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? ???
  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? Yes
  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? Yes
  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? ???
  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)? No
  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? No
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