HTN: Fiber (2007)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To determine the effects of long-term supplementation of arabinogalactan (a soluble, nonviscous dietary fiber) isolated from larch and from tamarack on serum lipids, glucose and insulin levels.
Inclusion Criteria:
Healthy men and women 18 to 55 years old were included although there were some mildly hypercholesterolemic subjects in each group.
Exclusion Criteria:
There is no mention of exclusion criteria.
Description of Study Protocol:
  • Recruitment: No discussion of method of recruitment
  • Design: Randomized double-blind, placebo controlled parallel clinical trial with a six-month duration. Baseline measures were collected and subjects were randomized to one of three groups: Placebo; larch arabinogalactan; tamarack arabinogalactan. Interventions occurred for six months with measurements taken monthly.
  • Blinding used: Double-blinded with placebo selected because of its similar appearance to the arabinogalactan supplements. 


  • Control Group: 8.4g per day rice starch consumed in a beverage or food (N=16)
  • Larch Arabinogalactin Group: 8.4g per day consumed in a beverage or food (N=18) 
  • Tamarack Arabinogalactin Group: 8.4g per day consumed in a beverage or food (N=19).

Statistical Analysis

  • Repeated-measures ANOVA was used to determine the effect of arabinogalactin
  • Two-sided P-values used
  • A subset of mildly hyperlipidemic subjects from each group was analyzed using the same methods. 
Data Collection Summary:

Timing of Measurements

 At baseline and at the end of each month of intervention (Months One through Six).

Dependent Variables

  • Plasma lipids and apoproteins including plasma cholesterol, triglycerides, HDL-C, LDL-C, apolipoprotein A-1 and apolipoprotein B (methods of measurement was not discussed for any of the variables)
  • Plasma insulin and glucose
  • BP
  • Weight 
  • GI symptoms including frequency of stools, consistency of stools, degree of intestinal bloating and degree of flatulence.

Independent Variables

  • 8.4g per day of rice starch added to diet
  • 8.4g per day of arabinogalactin isolated from larch added to diet
  • 8.4g per day of arabinogalactin isolated from tamarack added to diet.
Description of Actual Data Sample:
  • Initial N: Not mentioned
  • Attrition (final N): 54 completed the protocol (28 men)
  • Age: 18 to 55 years old; mean, 29 years
  • Ethnicity: Not discussed
  • Other relevant demographics: None
  • Anthropometrics: Values not given: There were no differences among the three groups at baseline for age, body weight, body mass index or dietary components of kcalories, fat, carbohydrate, protein, choleserol and soluble and insoluble fiber.
  • Location: St. Paul, MN.


Summary of Results:

Other Findings

  • There were no changes from baseline for any of the groups for serum cholesterol, triglycerides, HDL-C, apolipoprotein A, apolipoprotein B, cholesterol:LDL, LDL:HDL or insulin
  • Each group had decreases in serum glucose from baseline (P<0.05 to P<0.01), however all values were within normal ranges
  • There were no differences among groups for GI symptoms reported, except for increased flatulence at Month One for the Arabinogalactan groups (P<0.05).
Author Conclusion:
  • There were no differences among groups for any measured endpoint
  • Results from supplementation with arabinogalactan, in combination with data in the literature clearly illustrate that health benefits obtained from different dietary fibers vary and are dependent on fiber type and source.
Funding Source:
University/Hospital: University of Minnesota St. Paul
Reviewer Comments:
  • No discussion of recruitment methods, activity, alcohol use, smoking or ethnic differences
  • Three-day diet records were collected from each subject each month, however data was not presented
  • Dietary intake did not change during the study, with the exception of the supplemented starch or fiber.
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? No
  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? ???
3. Were study groups comparable? ???
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) ???
  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.) 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%.) ???
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? ???
  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? No
  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? No
  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? 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? No
  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? ???
  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? No
  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? ???
  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)? ???
  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? ???
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? N/A
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