EAL

DM: Carbohydrates (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

1. To determine whether patients taught to increase their intake of high-fiber foods in an outpatient setting using customary personnel and time allotments would increase their intake of fiber.

2. To determine whether these patients demonstrate improved diabetes control and decreased serum lipids.

3. To examine correlations among changes in nutrient intake and changes in diabetes control and serum lipids.

Inclusion Criteria:

Individuals with type 2 diabetes between 21 and 65 years of age
Fasting plasma glucose > 140 mg/dl at time of recruitment

Exclusion Criteria:

Patients receiving insulin therapy or sulfonylurea drugs
Severe illnesses other than diabetes

Description of Study Protocol:

Recruitment

From the outpatient medical service at the University of Virginia Primary Care Center during routine office visits.

Design

Comparison, by type of diet ("ADA diet", increased fiber diet, increased fiber diet + oat bran, and control), of glycemic and lipid control in individuals with type 2 diabetes at induction into study and six weeks after first education visit.

Blinding used (if applicable)

none

Intervention (if applicable)

Subjects were randomized into four groups. Patients in the dietary intervention groups were taught low-calorie diets and advised to lose 0.5-1.0 kg/wk, with changes being made, not just for fiber, but for other macronutrients as well:

ADA group: 50% carb, 20% protein, 30% fat, with intake of simple sugars, saturated fat and cholesterol limited
Increased fiber (IF) group: 55% carb, 15% protein, 30% fat with intake of simple sugars, saturated fat and cholesterol limited. Patients were encouraged to limit meats to 3-4 oz/d , increase fiber intake to 20-30 g/d, and eat one serving of dried beans daily
Increased fiber with oat bran (IFOB) group: The IF diet + 50 g oat bran per day (13.2 g dietary fiber, including 4.6 g soluble fiber)
Control group: Foot care instruction replaced nutritional counseling

Uniform counseling procedures were used: regulation of amount of time dietitians spent with subjects (50 min at baseline, 30 min at 2 wks and 6 wks); use of standardized teaching materials and schedules.

Statistical Analysis

Analysis of variance (with an accompanying Duncan's multiple range test)
Most data were evaluated in terms of individual patients' changes from baseline (using each subject as his/her own control and eliminating much patient-to-patient variability)
t-test for specific pairs of groups

Data Collection Summary:

Timing of Measurements

Induction into study, 2 weeks after 1st counseling visit, 6 weeks after 1st counseling visit

Dependent Variables

Fasting plasma glucose (FPG) (glucose oxidase method)
Fasting plasma insulin (charcoal-separation method, Albano, Acta Endocrinol 1972)
Insulin antibodies (charcoal-separation method, Albano, Acta Endocrinol 1972)
HbA_1c(Helena Quik Column total fraction method)
Serum cholesterol (enzymatic assay with cholesterol esterase and cholesterol oxidase)
HDL-cholesterol (preciption with dextran sulfate and magnesium sulfate)
Weight

Independent Variables

Dietary fiber, as well as carbohydrate, protein, fat (3 day food records, analyzed using standard references - Pennington 1980, Anderson 1980)

Control Variables

none given

Description of Actual Data Sample:

Initial N: 60

Attrition (final N): 52 (18 males, 34 females). 1 subject from the ADA group, 2 from the IF group, 2 from the IFOB group, and 4 control subjects did not return for follow-up visits.

Age: Mean of 53.2 years (no difference among groups)

Ethnicity: 38 black, 1 oriental, 14 white

Other relevant demographics:

mean duration of known diabetes: 5.5 yrs (no difference among groups)
mean highest grade of education: 8.3 yrs (no difference among groups)
Low SES

Anthropometrics: Mean of ideal body weight: 140% (control group heavier than IF group, p<0.05)

Location: University of Virginia School of Medicine, Charlottesville, VA

Summary of Results:

Variables	ADA Group n= 15 Change from baseline mean±SEM	IF Group, n= 12 Change from baseline mean±SEM	IFOB Group n= 13 Change from baseline mean±SEM	Control Group n=12 Change from baseline mean±SEM	Statistical Significance of Group Difference
HbA_1c (%); 13.7% upon induction into study+	-1.25	-2.08*	-1.73	+0.72	* statistically significant difference from control group, p < 0.05
FPG (mg/dl); 235 mg/dl upon induction into study++	-30.3±15.3	-58.0±12.3*	-40.0±1*	+4.6±8.8	* statistically significant difference from ADA and control groups, p<0.05
Fasting serum cholesterol (mg/dl); range of 221-246 upon induction into study+	-3.2±12.3	-40.3±9.2*	-28.6±11.4	+0.9±7.6	* statistically significant difference from ADA and control groups, p<0.05
Dietary fiber (g/d); range of 11-12 g/d upon induction into study+	+2	+8*	+15*	-3	* statistically significant difference from ADA and control groups, p<0.05
body weight (kg	-1.44	-0.66	-2.28*	--.44	* statistically significant difference from control group, p<0.05

+ No statistical difference among groups at induction into study

++ No statistical difference among groups at induction into study; Glucose levels had dropped in 3 subjects to slightly below 140 mg/dl at the time those subjects actually began the study

Other Findings

Five subjects were found to have insulin antibodies. After data for those patients were deleted, there were no statistically significant changes in any group for plasma insulin levels at either follow-up visit .
While HDL-cholesterol levels dropped slightly in all groups (-0.5 to - 4.8 mg/dl), there was no significant difference between groups.
Carbohydrate intake in the ADA, IF, and IFOB groups increased by 4-6% of calories whereas the control group intake decreased by 3%. All groups significantly different from control group, p < 0.05.
Fat intake decreased in the ADA, IF, and IFOB groups by 4-7% of calories, whereas the control group intake increased by 2%. All groups significantly different from control group, p<0.05.
There was no statistically significant association between weight loss and changes in FPG, HbA_1c, serum cholesterol and HDL-cholesterol.
The increase in dietary fiber was related to the decrease in FPG, serum cholesterol and HDL-cholesterol, but not HbA_1c.

Author Conclusion:

Patient education to an indigent population was delivered under circumstances similar to those that exist in many outpatient health care settings. The time allotted for each patient totaled only 2 hr over a 6-wk period
Subjects taught to eat an increased amount of high-fiber foods and given high-fiber supplements increased their reported fiber intake.
The increased fiber in the diet was tolerated well, and increased fiber and carbohydrate and decreased dietary fat were associated with decreases in fasting plasma glucose.
Increased fiber intake was also associated with reductions in total serum cholesterol and high-density lipoprotein cholesterol levels
Changes in fiber, carbohydrate, and fat intake were unrelated to changes in weight, serum insulin levels, or HbA_1c levels over the study period.

Funding Source:

University/Hospital:

University of Virginia

Reviewer Comments:

This is a well conducted study (primary and secondary authors are master's level registered dietitians), specifically
- study includes a number of the essential components of research design, commonly missing in other studies, for example randomized assignment method provided (stratified by age, sex, FPG, and % IBW)
- Possible bias in nutrition counseling were taken into consideration in the study design (time-on-task was the same for all groups; standardized curricula were used)
- Authors have diligently tried to eliminate confounders. One confounder missed could be the following: while patients with severe illnesses other then diabetes were excluded, many patients of the type described do take lipid/hypertensive or other medications, and adjusting the dose could affect outcomes (e.g.: lipid results).
This is a "real-world" study, where patients are given some education, and asked to follow certain guidelines, but do not eat in a controlled environment, and were not provided with supplements except for the fiber supplement (oat bran) provided to one group.
This is a 1985 study and uses the term "ADA diet" which is obsolete.

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.)	Yes
	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?		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?	???
	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?	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.)	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?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	???
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	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?	???
	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)?	???
	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