EAL

DM: Carbohydrates (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine the effectiveness and acceptability of high-carbohydrate, high-fiber diets in 14 men with diabetes followed for 4 years.

Inclusion Criteria:

Men with diabetes who had received high-carbohydrate, high-fiber diets while hospitalized.

Exclusion Criteria:

returned to homes out-of-state
unsuitable candidates for long-term follow-up on a highly structured diet regimen

Description of Study Protocol:

Recruitment: From a group of 37 men who had received high-carbohydrate, high-fiber diets while hospitalized.

Design: Comparison, by "diet setting (hospitalized, home), of glycemic and lipid control over an average of 4 years in 14 men with diabetes (11 type 2; 3 type 1)

Blinding used (if applicable)

Intervention (if applicable)

Three diets:

Control (usual) diet in hospital (7-10 days): Weight maintenance, with 43% of energy from carb, 18% from protein, 39% from fat, and 20 g plant fiber daily
High-carbohydrate, high fiber diet (2 weeks): Weight maintenance with 70% energy from carb, 19% from protein, 11% from fat, and 65 g plant fiber daily
High-fiber maintenance diet (average 4 yrs): 55-60% energy from carb, 20% from protein, 20-25% from fat, 100 mg/d cholesterol, and 40-50 g plant fiber.

During hospitalization weight and outcome measures were taken daily, and averaged during the last 3 days of each period; For follow-up, patients returned every 2-3 months for outcome measures and dietary assessment (24-hr recalls, 7-day surveys of food frequency, randomly assigned 24-hr reports).

Statistical Analysis

not mentioned

Data Collection Summary:

Timing of Measurements

Last 3 days of each hospitalization period; last 3 outpatient visits

Dependent Variables

Glycosylated hemoglobin (Glycosylated hemoglobin set, Palo Alto; last 2 yrs of study by Corning electrophoresis method)
Fasting glucose
Fasting cholesterol
Fasting triglycerides

Independent Variables

Adherence to high-fiber maintenance diet (determined by a point system, described in article)

Control Variables

Weight
Diabetes medication (insulin/oral agents)

Description of Actual Data Sample:

Initial N: 37 (all male), convenience sample of 21 selected for outpatient follow-up

Attrition (final N): data from 14 subjects used

Age: mean of 53 years, range of 36-70 (at baseline)

Ethnicity: not provided

Other relevant demographics: diabetes duration mean, 8 years (range < 1 yr to 20 yrs) (at baseline)

Anthropometrics: body weight, 105% of desirable weight (1959 Metropolitan Life Insurance Co tables), range 82-115%

Location: Veteran's Administration, Lexington, KY

Summary of Results:

Variables	Control diet (C)(n=14)* Mean ± SEM	High-Carbohydrate, High-Fiber diet (HCF) (n=14)* Mean ± SEM	High-Fiber Maintenance Diet (HFM) (n=14)* Mean ± SEM	Statistical Significance among groups
Fasting glucose (mg/dl)	162±13	158±16	166±8	NS
Fasting cholesterol (mg/dl)	198±10	147±7+	177±10+	+different from other two groups, p < 0.5
Fasting triglycerides (mg/dl)	133±10	136±11	101±9+	+different from other two groups, p < 0.5

* measurements for the control diet and the high-carbohydrate high-fiber diet were averaged from the last three days on the diet. Results for the high-fiber maintenance diet were an average of the last 3 outpatient visits.

Other Findings

Glycosylated hemoglobin (not done during hospitalization period) was a mean of 11 (range of 7.1-12.4; normal 6.5% to 8.5%)
Average body weight during the C and HCHF diets was similar (161-164 lb). Half of the patients maintained stable body weights over the follow-up period. Four patients lost between 9 and 18 lb, and 3 patients gained between 7 and 11 lb.
An average of 7 valid/acceptable food intakes was obtained per patient over approximately 1-1.2 to 7 years of follow-up, with adherence rated as excellent for 3 subjects, good for 6 subjects, fair for 1 subject, and poor for 1 subject. Three subjects were not evalated.
All subjects were taking insulin during the control period; for the HCHF period, insulin was discontinued in 9 of the 11 type 2 subjects; for the type 1 subjects, insulin doses were 32% lower on HCHF than on control. During the HFM diets, all 11 type 2 subjects were maintained for a number of months without insulin or or oral agents; however, most gradually went back on oral agents.

Author Conclusion:

The long-term effects of high-carbohydrate, high-fiber diets for patients who have consumed such diets for approximately 48 months are encouraging. These diets are practical and palatable for the motivated individual who desires better diabetic control and lower serum lipid concentrations.

Funding Source:

University/Hospital:

University of Kentucky College of Medicine

Reviewer Comments:

This study presents long-term (4 year) follow-up of subjects asked to follow a high-carbohydrate fiber maintenance in the home setting. No other studies have attempted to do such task. That said, there are a number of problems with the study:

the subjects were a convenience sample, with the subjects thought to be the most compliant being chosen.
Based on glycosylated hemoglobin values none of the subjects were ever in "good control". So, the results of this study may not apply to those who can achieve good or excellent control
Results do not apply to the general population of people with diabetes:
- study does not include women
- subjects were excluded if they were considered "unsuitable candidates for long-term follow-up on a highly structured diet regimen
Covariates were not considered when presenting results (e.g. medications)

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?		No
	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?	???
	2.2.	Were criteria applied equally to all study groups?	N/A
	2.3.	Were health, demographics, and other characteristics of subjects described?	???
	2.4.	Were the subjects/patients a representative sample of the relevant population?	No
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?		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?		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?	???
	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?	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?	N/A
	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?		???
	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?	???
	7.5.	Was the measurement of effect at an appropriate level of precision?	???
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	???
	7.7.	Were the measurements conducted consistently across groups?	N/A
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?	No
	8.2.	Were correct statistical tests used and assumptions of test not violated?	???
	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)?	No
	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