DM: Carbohydrates (2007)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To determine whether the use of low glycemic index foods over a longer time period would result in improved metabolic control in type 1 and type 2 diabetic subjects.
Inclusion Criteria:
None specifically mentioned.
Exclusion Criteria:
None specifically mentioned.
Description of Study Protocol:

Recruitment

Before entry into the study, all patients had been seen regularly in the department.

Design

Randomized Crossover Trial.

Blinding used (if applicable)

Not used.

Intervention (if applicable)

After run-in period of 15 days, patients assigned to either high mean glycemic index (64 +/- 2%) or low mean glycemic index (38 +/- 5%) diet for 5 weeks each.  Both diets were equivalent in terms of nutrient content and total and soluble fiber content.

Statistical Analysis

Statistical comparisons using Student's t tests for paired data were used irrespective of the order of the test.  No order effects were observed.

Data Collection Summary:

Timing of Measurements

Patients were asked to do at least 3 blood glucose measurements every day, 1 fasting and 2 postprandially (2 hours after meals).  Fasting random venous blood samples also obtained at start and completion of each study period.

Dependent Variables

  • Plasma glucose measured using glucose oxidase method
  • Fructosamine measured using modified colorimetric procedure
  • Plasma lipids measured using standard methods
  • Insulin binding 

Independent Variables

  • High mean glycemic index (64 +/- 2%) or low mean glycemic index (38 +/- 5%) diet for 5 weeks each.  Both diets were equivalent in terms of nutrient content and total and soluble fiber content.
  • Patients kept food diaries for compliance, reviewed by RD

Control Variables

 

Description of Actual Data Sample:

Initial N: 18 patients, 12 type 1, 6 type 2, 12 men, 6 females

Attrition (final N):  18

Age:  mean age 47.2 +/- 11.6 years

Ethnicity:  not mentioned

Other relevant demographics:  BMI 24.8 +/- 2.6 

Anthropometrics:

Location: France

 

Summary of Results:

Other Findings

There were no statistically significant differences between type 1 and type 2 patients.

At the end of the study periods, the following variables were improved on the low compared to the high glycemic index diet:

  • fructosamine (3.9 +/- 0.9 vs 3.4 +/- 0.4 mmol/l, p < 0.05)
  • fasting blood glucose (10.8 +/- 2.8 vs 9.6 +/- 2.7 mmol/l, p < 0.02)
  • 2 hour postprandial blood glucose (11.6 +/- 2.9 vs 10.3 +/- 2.5 mmol/l, p < 0.02)
  • mean daily blood glucose (12.0 +/- 2.5 vs 10.4 +/- 2.7 mmol/l, p < 0.02)
  • serum triglycerides (1.5 +/- 0.9 vs 1.2 +/- 0.5 mmol/l, p < 0.05)

No significant differences were found in body weight, HbA1c, insulin binding to erythrocytes, insulin and drug requirements, and other circulating lipids (cholesterol, HDL-cholesterol, phospholipids, apolipoprotein A1, apolipoprotein B).

 

 

Author Conclusion:
We conclude that a low glycemic index diet is beneficial in the management of type 1 and type 2 diabetic patients on a long-term basis, since the improvement of blood glucose control and plasma lipid levels may be of a major importance in the prevention of micro- and macro-angiopathy.  Any systematic application to long-term dietary use will require a much more comprehensive classification of foods.  It will also require a better understanding of nutrient interactions in foods and meals if the therapeutic potential of this maneuver is to be realized.
Funding Source:
University/Hospital: Pierre and Marie Curie University (Paris France)
Reviewer Comments:
Recruitment methods and 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? ???
  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? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
3. Were study groups comparable? N/A
  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.) N/A
  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? 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? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  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? 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? Yes
  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)? N/A
  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? ???
  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