DM: Carbohydrates (2007)
- diagnosis of type 2 diabetes
- taking medications for glycemic control
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.
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
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
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Standard Carbohydrate Diet
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High-Carbohydrate Diet
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P value
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Insulin Resistance, HOMA-R
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2.18±1.11
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1.74±0.65
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0.0386
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LDL-chol, mmol/l
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3.20±1.08
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2.87±0.82
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0.0250
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HDL-chol, mmol/l
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1.01±0.24
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0.87±0.18
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0.0011
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Triglycerides, mmol/l
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1.4±0.51
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1.58±0.49
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0.0358
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The correlation between the FPG high-carbohydrate/standard carbohydrate ratio and HOMA-R on the standard carbohydrate diet was -0.434, P=0.0378.
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.
Quality Criteria Checklist: Primary Research
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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 | |