DF: Diabetes (2008)

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

To correlate glycemic and insulin responses to the dietary fiber content of commonly-used cereal meals.

Inclusion Criteria:
  • Type 2 diabetes
  • Diet-controlled
  • Saw a dietitian within the past 12 months.
Exclusion Criteria:

Not described.

Description of Study Protocol:
  • Recruitment: Not described
  • Design: Comparison of the effect of four cereal grain dishes (pasta and fiber, pasta, rice, barley) on glycemic control and insulin response in 10 diet-controlled type 2 diabetics.


  • Participants received randomly-assigned test meals at two-week intervals during lunch in a "day hospital"
  • Patients saw the dietitian during the study period
  • Subjects did not take any hypoglycemics
  • Samples of the diets were chemically analyzed for fiber and starch content
  • The dietary fiber content of the four meals was determined as total dietary fiber by the AOAC procedure and non-starch polysaccharide by the Englyst method
  • In-vitro susceptibility to alpha-ammylase of the four meals was measured by the Wong method (means of at least five replicates)
  • In-vitro digestibility of the four pastas was measured by the Englyst method.

Composition of the Four Test Meals (per Meal)







Pasta and Fiber
























Statistical Analysis

Not described.

Data Collection Summary:
  • Timing of measurements: Not explicitly stated, but based on the figures, blood was sampled every 15 minutes from baseline to two hours after the test meal to measure glycemic response
  • Dependent variables: Glycemic response; no details provided
  • Independent variables: Dietary fiber content of the four meals
  • Control variables: Not described.
Description of Actual Data Sample:
  • Initial N: 10 (seven male, three female)
  • Attrition (final N): None reported
  • Age: 59.8±2.2 years
  • Ethnicity: Not described
  • Other relevant demographics: Diabetes duration 2.3±0.9 years
  • Anthropometrics: BMI, 24±0.6kg per m2
  • Location: Forlanini Hospital; Rome, Italy.
Summary of Results:



Pasta and Fiber (P+F)



Statistical Significance of Group Difference

Glycemic Response, mmol/L (90 minutes Post- Test Meal)

Not reported




P<0.01 (barley vs. rice)
P<0.05 (P+F vs. rice)
NS (P+F vs. barley)

Fiber Content of Meals

Total Fiber (g/100g Fresh Weight)* (Percentage Soluble)

1.6 (38%)

3 (27%)

1.4 (30%)

1.8 (29%)

Not reported

Non-Starch Polysaccharide (g/100g Fresh Weight)* (Percentage Soluble)

1.5 (53%)

3 (41%)

0.8 (60%)

1.75 (54%)

Not reported

 *Estimated from figure in the paper

Glycemic response lowest in Pasta and Fiber, followed by Barley, Pasta, then Rice.

Other Findings

In-vitro digestibility:

  • Rice and barley were similar and more digestible than pasta, 83% to 88% of the starch was rapidly digestible starch and only 6% was resistant starch
  • Both pasta and P+F had higher amounts of both slowly disestible starch (24%) and resistant starch (14% for pasta and 11% for P+F)
  • In-vitro digestibility at 20 minutes is highly correlated with glycemic response at 90 minutes (R=0.9, P<0.05).
Author Conclusion:
  • Results show that cereal food contains all three categories of starch, in highly variable proportions, depending on several factors (botanic origin, degree of damage, grinding and thermal processing)
  • The results of the in-vitro starch digestibility have been confirmed by data on in-vivo absorption, as demonstrated in the NIDDM patients by the high correlation between maximal glycemic plasma response and the rate of in-vitro starch hydrolysis.
Funding Source:
Government: National Institute of Nutrition (Rome Italy)
University/Hospital: Forlanini Hosptal (Rome Italy)
Reviewer Comments:
  • No description of eligibility criteria
  • No description of method of randomization
  • No description of study protocol (i.e., administration of test meal, blood draws)
  • No description of statistical methods
  • Primary focus was on the food composition analysis.
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? No
  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? No
  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.) No
  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? No
  4.1. Were follow-up methods described and the same for all groups? No
  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? ???
  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.) No
  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? No
  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? 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? No
  8.3. Were statistics reported with levels of significance and/or confidence intervals? No
  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)? No
  8.6. Was clinical significance as well as statistical significance reported? No
  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