DM: Carbohydrates (2007)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To observe the effects of a high carbohydrate diet on glucose tolerance and serum lipid profiles in Japanese patients with mild type 2 diabetes.
Inclusion Criteria:
  • diagnosis of type 2 diabetes
Exclusion Criteria:
  • taking medications for glycemic control
Description of Study Protocol:

Recruitment :  subjects were recruited from patients hospitalized in the metabolic ward of a medical university hospital

Design

  • after 1 week of FPG measurements below 150 mg/dl, subjects assigned to either a standard carbohydrate diet (S) or a high-carbohydrate diet (H) for 7 days
  • after 7 days, OGTT and fasting serum lipids obtained
  • then, the diet was crossed over for another 7 days
  • OGTT and fasting serum lipids repeated

Blinding used (if applicable):  none

Intervention (if applicable)

  • diet composition
    • standard carbohydrate:  55-60% CHO, 15-18% protein, 22-30% fat
    • high-carbohydrate:  78-80% CHO, 14=16% protein, 4-8% fat 

Statistical Analysis

  • all continuous variables expressed as the mean ± SD
  • the differences in the background characteristics or various parameters between the groups H and S were analyzed by Mann-Whitney U-test or by Fisher's exact test.
  • the effect of the stratification of various parameters on glucose tolerance was evaluated by Fisher's PLSD test
  • Wilcoxon signed-ranks test was applied to evaluate statistical significance between each parameter of the S diet vs. the H diet.
  • Linear regression was performed and Pearson's correlation coefficient was obtained.

 

Data Collection Summary:

Timing of Measurements:  measures of glycemic control and serum lipids performed after each 7-day diet test period

Dependent Variables

  • FPG
  • AUG for area under the glucose concentration-time curve during OGTT
  • Insulinogenic index:  (IRI at 30 minutes during OGTT-fasting IRI)/plasma glucose at 30 min during OGTT-FPG)
  • AUI- area under the insulin  concentration-time curve during OGTT
  • HDL
  • LDL
  • triglycerides
  • serum leptin
  • homeostasis model assessment insulin resistance (HOMA-R)
  • homeostasis model assessment beta-cell function (HOMA-B)

Independent Variables

  • diet composition
    • standard carbohydrate:  55-60% CHO, 15-18% protein, 22-30% fat
    • high-carbohydrate:  78-80% CHO, 14=16% protein, 4-8% fat 

 Control Variables

  • age
  • length of hospitalization

 

Description of Actual Data Sample:

Initial N:24; 9 female, 15 male

Attrition (final N): 24

Age: 54.5±11.0 yrs

Ethnicity: not specified

Other relevant demographics: HbA1c 7.2±1.1%

Anthropometrics: BMI 26.3±3.4. 

The H group had significantly higher age (59 vs.  51 years), FPG, PG1 and AUG than the S group ; but no other differences in characteristics between groups

Location: Japan

 

Summary of Results:

 

 

 
Standard Carbohydrate Diet
High-Carbohydrate Diet
P value
Insulin Resistance, HOMA-R
2.18±1.11
1.74±0.65
0.0386
LDL-chol, mmol/l
3.20±1.08
2.87±0.82
0.0250
HDL-chol, mmol/l
1.01±0.24
0.87±0.18
0.0011
Triglycerides, mmol/l
1.4±0.51
1.58±0.49
0.0358

Other Findings

The correlation between the FPG high-carbohydrate/standard carbohydrate ratio and HOMA-R on the standard carbohydrate diet was -0.434, P=0.0378.

 

 

Author Conclusion:

The present study shows that an 80% high-carbohydrate diet for 1 week reduced HOMA-R in patients with mild type 2 diabetes mellitus and improved glucose tolerance in two-thirds of the patients.

Improvement if FPG was predicted from HOMA-R on a standard carbohydrate diet.

Hypertriglyceridemia did not seem to be a contraindication of a high -carbohydrate diet.

Funding Source:
Reviewer Comments:
One week is too short a time to draw conclusions about the effects of dietary change on serum lipids.  Dietary compliance was not monitored.  Quasi-random method used to allocate diets.
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? Yes
  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? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  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? 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? No
  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? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  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? N/A
  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? 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? ???
  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? Yes
  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? 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? No
  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)? Yes
  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? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
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