DF: Diabetes (2008)

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

To compare the effect of guar incorporated into crispbreads, with that of unprocessed high-fiber foods on blood glucose concentrations in diabetic volunteers.

Inclusion Criteria:
  • Diabetic (five insulin-dependent, one controlled by diet alone)
  • Previous participants in a study testing the effect of guar and high-fiber foods on diabetic control.
Exclusion Criteria:

Not described.

Description of Study Protocol:


Diabetic subjects that had participated in a previous study examining the impact of guar and high-fiber foods on glycemic control were invited to participate.


  • Subjects consumed one of seven test breakfasts every two to four weeks over 4.5 months
  • Following an overnight fast and administration of normal medication, dosage meals were eaten over 15 to 20 minutes
  • Digital blood samples were collected and analyzed for glucose level every 30 minutes, from time zero to 180 minutes after the meal.

Blinding Used

  • N/A
  • Blood glucose measurements.


  • Seven breakfasts were tested:
    • Whole-meal bread (88g): 9.0±1.2g fiber
    • Whole-meal bread (46g) and guar crispbread (7g): 12.4±1.5g fiber
    • Whole-meal bread (46g) and soy beans (96g): 16.5±2.0g fiber
    • Guar crispbread (7g) and soy beans (96g): 19.8±2.9g fiber
    • Soy beans (75g) and lentils (41g): 15.5±1.7g fiber
    • Corn flakes (22g) and whole-meal bread (45g): 7.7±1.4g fiber
    • Porridge oats (26g) and whole-meal spaghetti (27g): 4.8±0.8g fiber.
  • Edam, cheddar and cottage cheese were used to balance the fat and protein of the guar and leguminous-seed meals, which also included 120g tomato and 500±50ml tea, made with 50ml milk
  • The methods for all studies were as follows:
    • Following a fast, the meal was eaten in 15 to 20 minutes
    • Blood was collected (via finger-prick) at zero, 30, 60, 90 and 120 minutes and analyzed for glucose levels.

Statistical Analysis

  • Mean with standard error
  • Student’s paired T-test.
Data Collection Summary:

Timing of measurements: Blood was collected at zero, 30, 60, 90 and 120 minutes and analyzed for glucose

Dependent variables: Glucose

Independent Variables

  • Quantity of guar gum (crispbread) consumed
  • Quantity of unprocessed high-fiber foods consumed.

Control Variables


Description of Actual Data Sample:
  • Initial N: Six (two male, four female)
  • Attrition: Not described
  • Age: 43±5 years
  • Ethnicity: Not described

Other Relevant Demographics

  • Five subjects receiving insulin (16u to 60u per day)
  • One controlled with diet alone..


99±3% IBW.


Central Middlesex Hospital, London, England.

Summary of Results:


Fasting Blood Glucose (mmol/L)

Three-Hour Glucose AUC (mmol/min/L)

Percentage of Bread Meal

Bread and Cheese




Bread and Guar Crispbread




Bread and soy beans





Guar Crispbread and Soy Beans




Soy Beans and Lentils




Porridge and Spaghetti





Cornflakes and Bread





Guar crispbread and soybean meal was the most effective at decreasing glycemic response to a breakfast meal.

Other Findings

All meals were well tolerated and consumed completely.

Author Conclusion:

The addition of a combination of a purified fiber product (guar crispbread), in combination with a leguminous fiber in its whole form (soy beans), led to a significant decrease in post-prandial glucose in diabetic individuals. This combination may decrease the quantity of fiber consumption required to see an effect.

Funding Source:
Reviewer Comments:
  • Poor description of limited study sample (six people; inclusion and exclusion criteria not explicitly specified)
  • Test meals varied in fiber and macronutrient content, so the effect of type of food vs. fiber content cannot be differentiated
  • Attrition (N=4) for two of the test meals may be responsible for lack of statistical significance
  • No discussion of limitations.
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? N/A
  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) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? No
  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%.) No
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? No
  4.4. Were reasons for withdrawals similar across groups? No
  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? 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? 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? No
  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? No
  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? 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)? Yes
  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? 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? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes