Fiber

DF: Cardiovascular Disease (2008)

Citation:

Schwab U, Louheranta A, Torronen A, Uusitupa M. Impact of sugar beet pectin and polydextrose on fasting and postprandial glycemia and fasting concentrations of serum total and lipoprotein lipids in middle-aged subjects with abnormal glucose metabolism. Eur J Clin Nutr. 2006 Sep; 60(9): 1,073-1,080. Epub 2006 Mar 8. PMID: 16523204.

 
Study Design:
Randomized Controlled Trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To examine the effects of sugar beet pectin (SBP) and polydextrose (PDX) on the following in middle-aged participants with abnormal glucose metabolism:

  • Fasting plasma glucose concentration
  • Serum lipid profile
  • Post-prandial glycemia.
Inclusion Criteria:
  • Normal liver, kidney and thyroid function
  • Body mass index (BMI): 35kg per m2
  • Age: 30 to 65 years
  • Fasting plasma glucose: Eight mmol per L 
  • B-GHbA1c: 8%
  • Total cholesterol: Under 7.5mmol per L 
  • Total serum triacylglycerols (TG): Under four mmol per L.
Exclusion Criteria:
  • Normal fasting and two-hour plasma glucose concentrations (up to six mmol and under 7.8mmol per L, respectively)
  • Use of lipid-lowering medication, oral hypoglycemic medication or insulin 
  • Unstable angina, history of myocardial infarction, coronary artery bypass graft, percutaneous transluminal coronary angioplasty within the past six months, transient ischemic attacks or malignancy
  • Use any nutrient supplements during the intervention or within one month of the beginning of the intervention.
Description of Study Protocol:

Recruitment

Newspaper ads.

Design

Placebo-controlled, randomized, parallel double-masked study. Subjects were randomly assigned to one of the following groups:

  • SBP group: Drink enriched in SBP obtained from Danisco Sugar (Helsinki, Finland and Nakskov, Denmark)
  • PDX group: Drink enriched in PDX formed by Danisco Sweeteners (Helsinki, Finland and Nakskov, Denmark; Litesse®)
  • The control group consumed a drink without fiber enrichment.

All the drinks had the same ingredients:

  • Water
  • Fructose (70g per L)
  • Sodium bentsoate (0.11g per L)
  • Potassium sorbate (0.23g per L)
  • Citric acid 0.5g per L.

Artificial flavor was raspberry in the SBP drink and blackcurrant in the PDX and control drinks. The SBP drink contained 40g per L SBP, of which 76% was soluble fiber and the PDX drink contained 40g per L PDX.

The following were collected after an overnight fast at Weeks Zero, Four, Eight and 12:

  • Weight
  • Blood pressure
  • Serum total and lipoprotein lipid concentrations
    • Samples were ultracentrifuged for 18 hours at the density of 1.006kg per L to remove very low-density lipoprotein (VLDL)
    • High-density lipoprotein in the infranate was separated from LDL by precipitation of LDL with dextran sulfate and magnesium chloride
    • Low-density lipoprotein-cholesterol concentration was calculated as the difference between the mass of cholesterol in the infranate and HDL
    • Enzymatic colorimetric methods with commercial kits (cholesterol, CHOD-PAP; triglyceride, GPO-PAP; Roche Diagnostics GmbH, Mannheim, Germany) were used to determine cholesterol and TG concentrations from whole serum and separated lipoproteins with an automated instrument (Kone Specific Clinical Analyzer, Kone Ltd, Espoo, Finland).
  • Fasting glucose
    • Concentration was analyzed using the glucose dehydrogenase method (Granutest 500, Merck KGaA, Darmstadt, Germany).
  • Plasma insulin concentration
    • Analyzed with a radioimmunoassay (RIA) method (Phadeseph Insulin RIA 100, Pharmacia Diagnostics, Uppsala, Sweden).

Blinding Used

Treatment assignment was double-masked

Intervention

  • 12-week trial providing daily liquid dose of four dL (16g fiber per day or placebo)
  • During the first week of the intervention, the subjects consumed only half of the daily dose (two dL)
  • The subjects met a clinical nutritionist at the visits of Weeks Zero, Two, Four and Eight, counseling on the modification of the quality of fat and increasing the intake of dietary fiber
  • The diet counseled was eucaloric and active weight-loss was not an aim. 

Statistical Analysis

  • Kolmogorov–Smirnov test with Lilliefors significance correction (Normality)
    • Variables with non-normal distribution (TG, HDL-cholesterol and GHbA1c) were log-transformed and the log-values were used in further analyses.
  • Area under the curve (AUC) of post-prandial plasma glucose, insulin and C-peptide was calculated using a Canvas software 
  • Two-factor repeated-measures ANOVA (changes within time and group and to examine the interaction between time and group)
  • Paired samples T-test was used for two-tailed comparisons within the groups
  • Student's T-test was used for between-group comparisons
  • Friedman's test and Wilcoxon matched-pairs signed-ranks test (changes in variables that did not become normal by log-transformation).
Data Collection Summary:

Timing of Measurements

The following were collected at Weeks Zero, Four, Eight and 12 visits:

  • Weight
  • Blood pressure
  • Blood samples were drawn after an overnight fast (12 hours)
    • Serum glucose
    • Serum insulin
    • Serum lipids
    • HgbA.

Dependent Variables

  • Serum total and lipoprotein lipid concentrations
  • Fasting glucose
  • Plasma insulin.

Independent Variables

Fiber intake in the form of SBP or PDX.

Control Variables

N/A.

Description of Actual Data Sample:
  • Initial N: 70 (31 male 39 female)
  • Attrition (final N): 66 (29 male 37 female)
  • Age
    • Control: 53±8 years
    • PDX: 55±7 years.
  • SBP: 51±9
  • Ethnicity: Finnish
  • Anthropometrics: Similar BMI and gender distribution between groups
  • Location: Kuopio University Hospital, Finland.
Summary of Results:

 HgbA1C

  • Increase in SBP and PDX groups (P<0.05)
  • No change in control group.

Glucose

  • No change in fasting glucose in PDX or SBP groups
  • Significant increase in fasting glucose in control group (P<0.05)
  • No difference in AUC for plasma glucose, C-peptide or insulin.

Blood Pressure

Decrease in blood pressure in SBP group.

Lipids

  • No decrease in total cholesterol in PDX or SBP groups
  • Decrease in total cholesterol in control group (P<0.05).

HDL

Increase in intervention group.

LDL

Decrease in control and PDX groups.

Triglycerides

No change in any group.

Other Findings

  • No difference in feelings of hunger, satiety, fullness or desire to eat
    • Decrease in feeling of hunger in PDX group over time.
  • All three groups reduced saturated fat and cholesterol and increased carbohydrate and fiber intake
  • Small but significant (under two kg) reductions in body weight were observed in control and PDX groups.
Author Conclusion:

In summary, in subjects with abnormal glucose metabolism, SBP and PDX do not have positive effect on fasting or post-prandial plasma glucose concentrations or plasma lipid profile.

Funding Source:
University/Hospital: University of Koupio (Finland)
Reviewer Comments:
  • No description of randomization method
  • No measure of compliance reported
  • No power calculation reported
  • Excluded four participants who dropped out, but two dropped out at the end and should have been included in the analysis
  • Stated the trial was double-blinded, but the flavor of the drink made by the study sponsor (Danisco) was raspberry and the other two drinks were blackcurrant flavor
  • Measured and reported many parameters in addition to outcome measures without adjustment for multiple comparison.
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? 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? ???
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? ???
  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? No
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? Yes
  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? No
  8.1. Were statistical analyses adequately described and the results reported appropriately? No
  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? N/A
  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? ???
  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? ???