DF: Cardiovascular Disease (2008)
Qi L, Vam Dam RM, Liu S, Franz M, Mantzoros C, Hu FB. Whole-grain, bran, and cereal fiber intakes and markers of systemic inflammation in diabetic women. Diabetics Care. 29: 207-211, 2006.

To evaluate the impact of dietary fiber on markers of systemic inflammation and endothelial dysfunction in women with type 2 diabetes.
Sub-set of The Nurses' Health Study
- Caucasian (over 95%)
- Ages, 30 to 55
- Self-reported diabetics, supplementary questionaire
- Use National Diabetes Data Group criteria.
- History of the any of the following at the first blood draw between 1989 and 1990:
- Myocardial infarction
- Coronary artery bypass grafting
- Percutaneous transluminal coronary angioplasty
- Stroke.
Recruitment
Analysis included women recruited and enrolled in the Nurses' Health Study in 1976.
Design
- Cross-sectional analysis of data from 902 self-reported diabetic women enrolled in the Nurses' Health Study
- Measurements of dietary intake were obtained in 1976, 1986 and 1990 using food-frequency questionnaires
- Fiber intakes along with demographics, BMI, physical activity, menopausal status, hormone therapy and duration of diabetes were assessed from survey tool
- Blood analysis was completed in 1989 and 1990 for inflammation and endothelial markers, C-reactive protein (CPR), tumor necrosis factor-a (TNF-R2), cellular cell adhesion molecule (1CAM)-1 and E-selectin.
Statistical Analysis
- Linear regression model to evaluate the associations between the dietary variables and plasma concentrations of the inflammatory markers (used average intake of nutrients from the questionaires)
- Dietary variables were analyzed in quintiles
- Logrithmic transformation of non-normally distributed variables (Inflammatory markers)
- Linear trend calculated by assigning median value for each quintile.
Timing of Measurements
- Semi-quantitative food frequency: Administered twice (1986 and 1990)
- Laboratory analysis: Administered once between 1989 and 1990.
Dependent Variables
- Markers of inflamation
- C-reactive protein (CPR)
- Tumor necrosis factor-a receptor 2 (TNF)
- Endothelial function
- Soluble intracellular cell adhesion molecule (ICAM)-1
- E-selectin.
Independent Variables
- Dietary intakes; fiber
- Total fiber
- Whole grains
- Germ
- Bran
- Glycemic load
- Glycemic index.
Control Variables
- Age
- BMI
- Alcohol consumption
- Physical acitivity (MET per week)
- Family history of coronary heart disease
- History of hypertnesion or hypercholesterolemia
- Oral diabetes medicaiton use
- Insulin use
- Post-menopausal status
- Hormone use
- Duration of diabetes
- A1C.
- Initial N: 902 (no males, 902 females)
- Attrition: N/A.
Age; Quintiles (Total Fiber)
- Q1: Mean, 57 years
- Q3: Mean, 58 years
- Q5: Mean, 60 years.
Ethnicity
- Caucasian: Over 95%
- Other groups not listed.
Anthropometrics; Quintiles (Total Fiber)
- Q1: 31
- Q3: 30.1
- Q5: 28.2 (significantly lower).
Other Demographics
Highest quintiles of whole grain and total fiber intake associated with significantly:
- Lower BMI
- Less alcohol intake
- More physical activity
- Less smoking.
Location
National Nurses' Health Study.
Age-Standardized Characterisitcs, According to Quintiles (Q) of Total Fiber and Whole-Grain Intakes
Variables |
Q1 |
Q2 |
Q3 |
Q4 |
Q5 |
P-Value |
|
Whole Grains |
4.75 |
9.82 |
1.53 |
2.28 |
3.54 |
|
|
|
CRP |
6.60 |
5.28 |
5.76 |
5.59 |
5.52 |
0.03 |
TNF |
2,647 |
2,552 |
2,571 |
2,439 |
2,435 |
0.017 |
|
Bran |
1.6 |
2.65 |
4.07 |
6.7 |
10.9 |
|
|
|
CRP |
6.29 |
5.61 |
6.33 |
5.48 |
4.96 |
0.007 |
TNF |
2,603 |
2,597 |
2,491 |
2,495 |
2,462 |
0.06 |
|
Glycemic Load |
TNF |
2,417 |
2,573 |
2,446 |
2,627 |
2,594 |
0.08 |
Glycemic Index |
CRP |
5.05 |
5.25 |
6.55 |
5.15 |
6.68 |
0.04 |
ICAM-1 |
307 |
296 |
310 |
322 |
331 |
0.07 |
|
TNF |
2,387 |
2,397 |
2,620 |
2,583 |
2,660 |
0.0008 |
Inflammatory Markers
- Whole grains
- Associated with a decreased concentration of CRP (P=0.03) and TNF-R2 (P=0.01)
- No effect on ICAM or E-selectin.
- Germ
- No effect on CRP, ICAM, E-selectin or TNF.
- Bran
- Associated with a decreased concentration of CRP (P=0.007)
- No effect on ICAM, E-selectin.
- Glycemic load
- No effect on CRP, ICAM or E-selectin.
- Glycemic index
- Associated with a decreased concentration of CRP (P=0.04) and TNF-R2 (P=0.0008)
- No effect on E-selectin.
- Increased intake of whole grains or low-glycemic index diet associated with lower markers of inflammation, as measured by CRP and TNF-R2
- The effect of whole-grain, bran and cereal fiber were independent of dietary glycemic index and an additional mechanism may be involved
- The authors recommend that patients with type 2 diabetes increase intake of whole-grain products and maintain a diet low in glycemic index.
Government: | NIH |
- This study showed an effect of dietary fiber, whole grains and bran in particular, on lower levels of CRP and TNF, but not the markers of endothelial function
- Their data also suggests that glycemic index is related to increased inflammatory markers
- The high subject number and good statistical analysis supports the roles of fiber and glycemic intake.
- Did not include data on current or historical glycemic control
- Utilized data from FFQ.
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? | 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.) | 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? | 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? | No | |
6.6. | Were extra or unplanned treatments described? | No | |
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? | No | |
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 | |