DF: Diabetes (2008)
Qi L, Rimm E, Liu S, Rifai N, Hu FB. Dietary glycemic index, glycemic load, cereal fiber, and plasma adiponectin concentration in diabetic men. Diabetes Care. 2005 May; 28 (5): 1,022-1,028. PMID: 15855561.
PubMed ID: 15855561
To examine the impact of dietary fibers, glycemic load and glycemic index on adiponectin concentration in men with type 2 diabetes mellitus.
- Male health professionals
- Aged 40 to 75 years
- Confirmed type 2 diabetes, as per the National Diabetes Group criteria.
- Evidence of
- Fatal coronary heart disease
- Non-fatal MI
- CABG
- Percutaneous transluminal coronary angioplasty
- Fatal stroke
- Non-fatal stroke at blood draw.
Recruitment
Male health professionals recruited to the Health Professionals' Follow-Up Study, nationally.
Design
- Cross-sectional analysis of 780 type-2 diabetic men enrolled in the Health Professionals' Follow-Up Study, that meet inclusion criteria
- Detailed dietary information regarding intake in the previous year was collected using semi-quantitative FFQ in 1986, 1990 and 1994. Cumulative average of the three FFQ was used.
- For the purposes of this study, data was collected on carbohydrate intake, fat intake, glycemic index, glycemic load and fiber
- Carbohydrate intake and fat intake were expressed as nutrient density
- Glycemic index, glycemic load and fiber were energy-adjusted, using residual method
- Blood samples were collected between 1993 and 1994 and analyzed for adiponectin
- Anthropometric and lifestyle questionnaires were administered once in 1986
- Physical activity was expressed as metabolic equivalents, based on self-report.
Statistical Analysis
- Linear regression (dietary intake and adiponectin levels)
- Quintiles (dietary variables)
- Adjustment for confounding variables
- Test for effect modifications (BMI, physical activity, alcohol consumption).
Timing of Measurements
- Food Frequency Questionnaire: Three times (1986, 1990 and 1994)
- Blood analysis: Once between 1993 and 1994
- Anthropometric and lifestyle questionnaires: Once (1986).
Dependent Variables
Serum adiponectin level.
Independent Variables
- Cereal fiber intake
- Dietary glycemic load
- Dietary glycemic index.
Control Variables
- Age
- BMI
- Smoking
- Alcohol consumption
- Physical activity
- Hypertension
- Hypercholesterol.
- Initial N: 780 (780 males, zero females)
- Attrition (final N): Not applicable.
Age
- Q1: 53±8 years
- Q2: 55±8 years
- Q3: 55±9 years
- Q4: 57±7 years
- Q5: 58±8 years.
Ethnicity
Not described.
Other Relevant Demographics
- Highest quintile of adiponectin were or had:
- Older
- Leaner
- More likely to consume alcohol
- More physically active
- More use of insulin
- Less hypertension
- Less hypercholesterolemia
- Less family history of MI.
Anthropometrics
No significant differences between quintiles.
Location
National, Health Professionals' Follow-Up Study.
- Carbohydrate: No significant effect on plasma adiponectin levels
- Glycemic index
- Decreasing adiponectin with increasing intake of high-glycemic index foods (P=0.005; multivariate modeling plus BMI)
- Adiponectin 13% lower in highest quintile of high-glycemic index food intake.
- Glycemic load
- Decreasing adiponectin with increasing intake of high-glycemic load foods (P=0.004; multivariate modeling plus BMI)
- Adiponectin 18% lower in highest quintile of high-glycemic load food intake.
- Total fiber: No significant effect on plasma adiponectin levels
- Cereal fiber
- Decreased adiponectin with increased intake of cereal fibers (P=0.043; multivariate modeling plus BMI)
- Adiponectin 19% lower in highest quintile of high-cereal fiber intake
- Attenuated with adjustment for magnesium.
- Vegetable fiber: No significant effect on plasma adiponectin levels
- Fruit fiber: No significant effect on plasma adiponectin levels
- Magnesium: Increased adiponectin levels with increased magnesium intake (P=0.011, multivaritae modeling plus BMI)
- Other results: Highest intake of cereal fiber and lowest glycemic load had highest adiponectin levels (P=0.0097).
Lower dietary glycemic index and glycemic load are associated with higher plasma adiponectin levels independent of fiber intake, indicating a potential benefit in type-2 diabetics; whereas cereal intake is associated with lower plasma adiponectin levels and may be less beneficial to individuals with type-2 diabetes.
Government: | NIH |
Data based on an average of three FFQ.
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? | Yes | |
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? | Yes | |
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? | Yes | |
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.) | Yes | |
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? | No | |
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.) | No | |
5.3. | In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? | No | |
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? | N/A | |
6.2. | In observational study, were interventions, study settings, and clinicians/provider described? | Yes | |
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)? | 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? | N/A | |
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 | |