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DF: Cardiovascular Disease (2008)

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

To examine the effect on blood lipids of yeast-derived beta-glucan fiber during eight weeks in hypercholesterolemic obese subjects, with a follow up of 12 weeks.

Inclusion Criteria:
  • Obese male subjects at more than 120% of ideal weight
  • Aged between 20 years and 60 years
  • Cholesterol concentrations more than 240mg per dL.
Exclusion Criteria:
  • Subjects taking cholesterol-lowering medication; hyperlidipidemia was secondary to hypothyroidism, diabetes mellitus or renal disease
  • Excluded from the analyses: Four subjects; reasons not mentioned.
Description of Study Protocol:

Recruitment

Subjects were recruited from the Beth Israel Deaconess Medical Center's Nutrition and from the local newspaper advertisements.

Design

  • Time-series study for 12 weeks
  • All subjects were under a run-in period of three weeks, followed by a period of eight weeks' treatment with yeast-derived beta-glucan fiber and a total, followed-up, of 12 weeks
  • Subjects completed, weekly, a three-day food record during the baseline and treatment periods
  • Each week, subjects completed questionnaires designed to gauge the effect of the product
  • There was no modification in their diets.

Blinding Used

Not used: Lab tests.

Intervention

Treatment Group: 15g of yeast-derived beta-glucan fiber per day.

Statistical Analysis

One-way analysis of variance, followed by Bonferroni correction to compare baseline and each period treatment when ANOVA was significant.

Data Collection Summary:

Timing of Measurements

  • Blood lipids collected weekly during the baseline (three weeks) and at the end of Weeks Seven, Eight and 12
  • Weight and BMI were measured during baseline and after Weeks Eight and 12.

Dependent Variables

  • Total cholesterol and HDL-cholesterol, measured directly 
  • LDL-cholesterol was calculated
  • Plasma triacylglycerols
  • Satiety, tolerance and acceptability ratings
  • Weight and BMI.

Independent Variables

Fiber: Yeast-derived beta-glucan fiber.

Control Variables

None.

Description of Actual Data Sample:
  • Initial N: 19 males
  • Attrition (final N): 15 males
  • Age: Mean, 51 years
  • Ethnicity: N/A
  • Other relevant demographics: Not mentioned
  • Anthropometrics: Weight and BMI matched at baseline to enroll only overweight subjects (BMI=27.7±5)
  • Location: Beth Israel Deaconess Medical Center, Boston, MA.
Summary of Results:

Plasma Lipids

  • Fiber consumption significantly reduced plasma total cholesterol by 8% at Week Seven and 6% at Week Eight (P<0.05), but not at Week 12
  • No significant differences were noted between baseline LDL-cholesterol and values at Weeks Seven, Eight and 12, when comparing individual groups, even though the ANOVA with repeated measures was highly significant; P<0.001
  • There was a tendency to reduce LDL-cholesterol to 8% at Week Eight
  • HDL-cholesterol increased significantly after fiber treatment; P<0.005. However, only at Week 12 was a group difference observed when compared to baseline; P<0.05
  • Triacylglycerol did not change.

Weight and BMI

There was no change in the weight and BMI before and after treatment.

Dietary Fiber

Intake was 17±3 at baseline and 19±5 (plus 15g yeast fiber) during treatment period.

Author Conclusion:
  • The yeast beta-glucan fiber lowered total cholesterol and was well tolerated
  • HDL-cholesterol was raised at Week 12 after the fiber was stopped
  • Yeast beta-glucan improved the lipid profile more than NCEP Step II diet, so it would be interesting to study whether there would be an additional benefits with both of them combined.
Funding Source:
Reviewer Comments:
  • The major problems with this study were the small sample size, which can increase the risk of type 2 error, and the inclusion only of males
  • The study also may have a conflict of interest, as the first author belongs to the company which issued the patent for the beta-glucan fiber, even though the research was conducted before the author went to work for this company.
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? No
  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? No
  2.4. Were the subjects/patients a representative sample of the relevant population? No
3. Were study groups comparable? N/A
  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? ???
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  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? ???
  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%.) Yes
  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? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  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? 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? No
  6.6. Were extra or unplanned treatments described? No
  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)? No
  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? No
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? No
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? No