DF: Diabetes (2008)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To determine the extent to which beta-glucan reduces the glycemic index (GI) of oat products and whether high levels of beta-glucan impair palatability.
Inclusion Criteria:
  • type 2 diabetes
Exclusion Criteria:
None specifically mentioned.
Description of Study Protocol:

Recruitment:  subjects drawn from patient pool at diabetes clinic and from respondents to public advertisements; subjects received a financial award for their participation

Design open-label, randomized crossover design with six treatment segments

Blinding used (if applicable): none

Intervention (if applicable):  subjects were given, in random order, test meals with 50 g of available carbohydrate in the form of

  • white bread (3 trials)
  • commercial oat bran breakfast cereal
  • prototype beta-glucan-enriched  (6.5%) breakfast bar
  • prototype beta-glucan-enriched (8.1%) breakfast cereal

Statistical Analysis

  • the significance of differences between mean glycemic response areas among the four test meals was assessed using a two-way ANOVA and after establishment of a significant F-value, by the Student-Neuman-Keuls procedure.
  • the incremental areas under the blood glucose-response curve, ignoring the area below the fasting level, were calculated geometrically.
  • the area under the curve for each food was expressed as a percentage of the mean area for the three white bread tests and the resulting mean values for all subjects represented the GI of the food.
  • four volunteers were asked to repeat test sessions and means of all the tests for the food were used to calculate the GI.


Data Collection Summary:

Timing of Measurements

  • capillary blood samples taken fasting and then 30, 60, 90,120, 150, and 180 minutes after the start of the meal

Dependent Variables

  • palatablility using a bipolar scale ranging from -3 (dislike extremely) to +3 (like extremely)
  • blood glucose response, using finger prick blood samples and analyzed using glucose oxidase method
  • total cholesterol, tryglycerides, and HDL using desktop Cholestech LDX analyzer

 Independent Variables

  •  test meals with 50 g of available carbohydrate in the form of
    • white bread (3 trials)
    • commercial oat bran breakfast cereal
    • prototype beta-glucan-enriched  (6.5%) breakfast bar
    • prototype beta-glucan-enriched (8.1%) breakfast cereal

Control Variables


Description of Actual Data Sample:

Initial N: 16; 10 men, 6 women

Attrition (final N): 16

Age: 61±1.8 y, range 46-70

Ethnicity: not specified

Other relevant demographics:

  • HbA1c  7.4±0.4%, range 5.5±11.4%


  • BMI 29±1.6, range 19.4-43.0

Location:  Canada

Summary of Results:

All meals were highly acceptable to volunteers.

The blood glucose levels for both the prototype beta-glucan bar and beta-glucan cereal were significantly lower at 60, 90, and 120 minutes than white bread (P<0.05). 


Incremental area under the blood glucose curve

Predicted GI

Observed GI

GI reduction of beta-glucan

Palatability Score

Oat Bran breakfast cereal



86±6 **




beta-glucan cereal






beta-glucan bar






 *significantly lower than for white bread

**significantly lower than for white bread

***significantly greater than the value for white bread (P<0.05)

Other Findings


Author Conclusion:
Each gram of betal-glucan can be expected to lower the GI of a food by four GI units and the effect is not attenuated by processing, including the use of fructose to enhance palatability.
Funding Source:
Reviewer Comments:
Inclusion/exclusion criteria not well described.
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? ???
  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? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  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%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  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? 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? Yes
  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? N/A
  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? 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)? No
  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? 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? No
  10.2. Was the study free from apparent conflict of interest? Yes