EAL

Diabetes and Carbohydrates

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To see if variations in the amount of fiber present in high carbohydrate diets had any impact on carbohydrate and lipid metabolism in patients with NIDDM.

Inclusion Criteria:

Diagnosis of type 2 diabetes mellitus based on criteria of the National Diabetes Data Group of Fasting Plasma glucose >140 mg/dl.

Exclusion Criteria:

Evidence of renal, hepatic or cardiovascular disease.

Description of Study Protocol:

Recruitment: not specified

Study design:

Randomized crossover design: 6 subjects with non-insulin dependent diabetes randomly assigned to 1 of 2 study diets for 4 weeks, followed by the other study diet for 4 week while confined to a Clinical Research Center.

Intervention:

2 study diets for 4 weeks each.

Blinding Used: not specified

Statistical analysis:

results expressed as mean ± standard error
analysis of variance for crossover design was used to determine significance between differences in group totals between the dietary periods.
coefficients of variation used to assess the amount of variation within individual subjects for glucose, insulin, and triglycerides

Data Collection Summary:

Timing of Measurements:

Fasting plasma glucose obtained weekly
Fasting and day-long hourly plasma samples (0800 – 1700 h) obtained on days 27 and 28 of each study period for glucose, insulin, TG, cholesterol, HDL-chol
Fasting blood sample obtained for HbA1c at the end of each study period.
24-hr urine collected the last 2 d of each study period.

Dependent Variables

Fasting plasma glucose
Fasting insulin
HbA1c
24-hr urinary glucose
Serum lipids

Independent Variables

Study diets prepared by staff of the GRC kitchen; 60% carbohydrate, 25% fat, 15% protein; high fiber diet: 26.7 g/1000 kcal and normal fiber: 11 g /1000 kcal.
level of physical activity and body weight remained stable during the study
increases in dietary fiber were achieved by changing white bread to whole wheat, fruit juice to whole fruit, refined cereals to whole grain, and by adding peanuts as a snack

Control Variables

Description of Actual Data Sample:

Initial N: 6 subjects, gender not specified

Attrition (Final N): 6

Age: 41 to 64 yrs

Ethnicity: not specified

Other relevant demographics: 3 treated with tolazamide, two treated with diet alone, and one treated with chlorpropamid

Anthropometrics: all less than 120% of ideal body weight; BMI 25.8 ±1.4

Location: Palo Alto, California

Summary of Results:

The results showed no significant difference in fasting plasma glucose and insulin, day-long glucose and insulin, fasting HbA1c, or 24-hour urinary glucose by study diet.

	High Fiber	Control
Fasting plasma Glucose, mg/dl	194±17	177±19
Fasting insulin, µU/ml	12±2	11±2
HbA1c, %	6.5	7.0
24-hr Urine glucose, mg/dl	28±13	31±15
TG, mg/dl	244±61	226±52
T-chol, mg/dl	199±11	189±9

Author Conclusion:

The present study provides practical information in regard to the long term effects of increased dietary fiber in individuals with relatively poorly controlled type 2 diabetes mellitus. Specifically, an increase in the estimated fiber content of the typical American diet from 11 to 27 g/1000 kcal did not lead to measurable improvement in overall plasma glucose, insulin, or lipid metabolism.

Funding Source:

Government:	VA HSR&D, NIH
University/Hospital:	Stanford University School of Medicine, VA Medical Center

Reviewer Comments:

These subjects had less than optimal glycemic control, which could interfere with the study results. For example, baseline HbA1c of 7% compared to the normal range for this lab of 3.8 to 5.5% and fasting plasma glucose approaching 200 mg/dl.

Also, we wouldn’t expect significant changes in HbA1c after 4 wk on a study diet.

Treatment goals for type 2 diabetes mellitus have changed since this study was done.

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?		???
	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?	???
	2.4.	Were the subjects/patients a representative sample of the relevant population?	???
3.	Were study groups comparable?		N/A
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	N/A
	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?	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?		Yes
	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?	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?	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?		No
	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)?	No
	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?	N/A
	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?	No
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