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
- Percutaneous transluminal coronary angioplasty
- Fatal stroke
- Non-fatal stroke at blood draw.
Male health professionals recruited to the Health Professionals' Follow-Up Study, nationally.
- 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.
- 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).
Serum adiponectin level.
- Cereal fiber intake
- Dietary glycemic load
- Dietary glycemic index.
- Alcohol consumption
- Physical activity
- Initial N: 780 (780 males, zero females)
- Attrition (final N): Not applicable.
- Q1: 53±8 years
- Q2: 55±8 years
- Q3: 55±9 years
- Q4: 57±7 years
- Q5: 58±8 years.
Other Relevant Demographics
- Highest quintile of adiponectin were or had:
- More likely to consume alcohol
- More physically active
- More use of insulin
- Less hypertension
- Less hypercholesterolemia
- Less family history of MI.
No significant differences between quintiles.
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.
Data based on an average of three FFQ.
Quality Criteria Checklist: Primary Research
|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|
|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|