Cardiovascular Disease and Micronutrients
To study the relative effect of tocotrienol supplements of different compositions (mixed alpha- plus gamma-, high gamma- or P25-complex tocotrienol) on blood lipids, fasting blood glucose and the excretion of 8-iso-prostaglandin F2alpha in healthy hypercholesterolemic men and women.
- Male or female adult
- Healthy (determined based on blood chemistry analysis and as the subjects reported on a medical history questionnaire)
- Initial baseline serum total cholesterol concentration was 5.17mmol to 7.76mmol per L
- Initial baseline LDL-cholesterol was greater than 3.36mmol per L
- Initial baseline triacylglycerol was less than or equal to 4.52mmol per L.
- Subjects currently (or within the previous three months) taking prescription medication known to have an effect on blood lipids
- Subjects currently (or within the past 30 days) taking bulk laxatives or dietary supplements to reduce blood cholesterol concentrations
- Women taking hormone replacement therapy or oral contraceptives for less than three months prior to the study
- Women taking hormone replacement therapy or oral contraceptives for more than three months prior to the study with varying dosages.
- Recruitment: Not described
- Design: Randomized, double-blind parallel design
- Blinding used: Supplements were sealed in bottles and labeled with a masked study number.
Intervention
- Subjects were randomly assigned to receive one of three tocotrienol supplements or placebo
- Additionally, they followed a NCEP Step 1 diet and followed a meal pattern including a regular daily lunch meal and consumed all capsules at the midday meal.
Statistical Analysis
- Subjects were ranked in descending order, blocked by four and randomly assigned to four groups according to their baseline LDL-cholesterol concentrations. Data collected at baseline and during the run-in-phase and supplementation phase were examined to test the assumption of normally-distributed residuals with the use of the Shapiro-Wilk test
- Comparison of the groups for values obtained during the run-in and supplementation phases and the calculated percentage change from the run-in phase to the supplementation phase was first carried out with two-way repeated-measures analysis of variance
- Because an interaction (group-by-time) was significant, one-way ANOVA was used to analyze the run-in and supplementation phases and the percentage change data, if the assumption of non-normally distributed residuals was met at each time point
- Variables for which the residuals showed evidence of being non-normally distributed at greater than or equal to one time point were ranked and one-way ANOVA was carried out on the rank data (Kruskal-Wallis one-way layout test)
- When significant group effects were detected, a post-hoc Tukey's honestly significant difference test was used to identify the pair that caused the significant difference
- Spearman's rank correlation coefficients were calculated to compare blood lipid and tocotrienol data and the correlation between blood lipid and urine data
- Demographic variables were summarized with frequencies and percentages.
Timing of Measurements
- Fasting blood samples from subjects were taken once at screening, on Days 19 and 21 during the Step 1 diet run-in phase and on Days 47 and 49 during the supplementation phase
- Urine samples (overnight; 12 hours plus morning void) were collected by subjects twice, on Day 19 or 21 during the Step 1 diet run-in phase and on Day 47 or 49 during the supplementation phase.
Dependent Variable
- Total cholesterol, measured enzymatically with the use of a validated method on a diagnostic autoanalyzer
- LDL-cholesterol, calculated with the use of the Friedwald's equation, where LDL equals total cholesterol, HDL-cholesterol (triacylglycerols divided by five)
- HDL-cholesterol, measured enzymatically with the use of a validated method on a diagnostic autoanalyzer; measured after the the precipitation of apolipoprotein B with the use of dextran sulfate
- Triglycerides, measured enzymatically with the use of a validated method on a diagnostic autoanalyze
- Glucose, measured with an automated glucose hexokinase enzymatic assay on a diagnostic autoanalyzer
- 8-iso-prostaglandin F2alpha, measured by radioimmunoassay after alkaline hydrolysis.
Independent Variables
Tocotrienol supplements:
- Mixed alpha plus gamma analyzed by normal-phase HPLC with the use of a Diol column
- High gamma analyzed by normal-phase HPLC with the use of a Diol column
- P25-complex tocotrienol analyzed by normal-phase HPLC with the use of a Diol column.
- Initial N: 68 healthy subjects (39 men, 29 females)
- Attrition (final N): 67 healthy subjects (38 men, 29 females)
- Age: 25 to 65 years
- Ethnicity: Not described
- Location: Not described.
Significance Levels Between Fasting Serum Levels and Treatment Group
Alpha- Plus Gamma- |
Gamma- |
P25-Complex |
|
Total Cholesterol |
Not significant |
Not significant |
Not significant |
LDL-Cholesterol |
Not significant |
Not significant |
Not significant |
HDL-Cholesterol |
Not significant |
Not significant |
Not significant |
Triacylglycerols |
Not significant |
Not significant |
Not significant |
Glucose |
Not significant |
Not significant |
Not significant |
8-iso-prostaglandin F2alpha |
Not significant |
Not significant |
Not significant |
Other Findings
When values for total cholesterol, HDL-cholesterol and glucose were expressed as a percentage change from the concentration during the run-in phase the increases in total and LDL-cholesterol were significantly greater (P<0.05) in the group consuming the alpha- plus gamma- tocotrienol supplement than those consuming the P25-complex supplement.
Supplementation with 200mg tocotrienols per day from three commercially-available sources had no beneficial effect on key cardiovascular disease risk factors in highly compliant adults with elevated blood lipid concentrations.
Industry: |
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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) | 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? | 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? | N/A | |
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? | Yes | |
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? | 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)? | N/A | |
8.5. | Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? | Yes | |
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? | N/A | |
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 | |