Cardiovascular Disease and Micronutrients
Citation:
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
The research purpose was to determine if supplemental vitamins C and E were effective in lowering serum lipids in healthy middle aged and older adults.
Inclusion Criteria:
- No known cardiovascular disease
- Aged 50 years or older.
Exclusion Criteria:
None listed.
Description of Study Protocol:
- Recruitment: Volunteers from a university-based outpatient clinic
- Design: Double-blind, placebo-controlled RCT (extensive randomization described)
- Blinding used: Both subjects and investigators blinded.
Intervention
- Group A (N=30): 1,000mg vitamin C
- Group B (N=30): 100 IU vitamin E
- Group C (N=30): Both 1,000mg vitamin C and 100 IU vitamin E
- Group D (N=30): Placebo.
Statistical Analysis
- Paired T-tests
- ANOVA
- Significance, P<0.05.
Data Collection Summary:
Timing of Measurements
Baseline and 75 days.
Dependent Variables
- Total serum cholesterol
- HDL-cholesterol
- LDL-cholesterol
- Triglycerides.
Independent Variables
- Group A: 1,000mg vitamin C
- Group B: 100 IU vitamin E
- Group C: Both 1,000mg vitamin C and 100 IU vitamin E
- Group D: Placebo.
Description of Actual Data Sample:
Initial N
120 (60 males, 60 females).
Attrition (Final N)
98 (19% attrition)
- Group A (N=27): 1,000mg vitamin C
- Group B (N=24): 100 IU vitamin E
- Group C (N=26): Both 1,000mg vitamin C and 100 IU vitamin E
- Group D (N=19): Placebo
Age
- Range: 50 to 75 years
- Mean: 60.5±7 years.
Ethnicity
Not described.
Anthropometrics
Investigators reported no significant differences at baseline, but:
- Mean serum cholesterol of four groups ranged from 171mg to 206mg per dL at baseline
- Mean triglyceride levels of four groups ranged from 152mg to 195mg per dL at baseline
- Mean LDL-cholesterol levels of four groups ranged from 97mg to 130mg per dL at baseline.
Location
Lebanon.
Summary of Results:
Change in Serum Lipids
|
Vit C
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Vit E
|
Vit C&E
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Placebo
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Pre
|
Post
|
Pre
|
Post
|
Pre
|
Post
|
Pre
|
Post
|
|
TG (mg/dL)
|
195
|
191
|
215
|
207*
|
152
|
144*
|
186
|
188
|
Cholesterol (mg/dL)
|
171
|
163*
|
178
|
167*
|
184
|
171*
|
206
|
212**
|
HDL-Cholesterol (mg/dL)
|
38
|
44*
|
32
|
43*
|
33
|
44*
|
37
|
36
|
LDL-Cholesterol (mg/dL)
|
97
|
80*
|
103
|
84*
|
121
|
101*
|
130
|
137*
|
* significantly different P<0.0001
**significantly different P<0.05.
Author Conclusion:
Supplementation with vitamins C and E can lower cholesterol and LDL levels and increase HDL levels in healthy middle-aged to older adults.
Funding Source:
Other: |
Reviewer Comments:
Quality Criteria Checklist: Primary Research
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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? | ??? | |
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%.) | No | |
4.3. | Were all enrolled subjects/patients (in the original sample) accounted for? | No | |
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? | Yes | |
6.3. | Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? | Yes | |
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? | 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)? | ??? | |
8.5. | Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? | N/A | |
8.6. | Was clinical significance as well as statistical significance reported? | No | |
8.7. | If negative findings, was a power calculation reported to address type 2 error? | N/A | |
9. | Are conclusions supported by results with biases and limitations taken into consideration? | No | |
9.1. | Is there a discussion of findings? | Yes | |
9.2. | Are biases and study limitations identified and discussed? | No | |
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 | |