EAL

DM: Carbohydrates (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

Compare the effects of sensible, low-glycemic-index dietary advice on dietary quality and food choice in children with type 1 diabetes over a 12-month period.

Inclusion Criteria:

age 8-13 years
diagnosis of type 1 diabetes for more than one year
regular attendance at the Melbourne Royal Children's Hospital Diabetes Clinic
no additional dietary restrictions
no immediate family members with diabetes
no current medications that would affect appetite
immediate family members were able to read and write English

Exclusion Criteria:

Excluded if not included above.

Description of Study Protocol:

Recruitment: subjects were regular patients at the Melbourne Royal Children's Hospital Diabetes Clinic

Design: children were randomized into two groups to receive dietary advice and were followed for 12 months. Groups were:

traditional carbohydrate exchange (CHOx), expected GI intake of 65-70%
flexible low-glycemic-index dietary advice (LowGI), expected GI intake of 50-55%

Blinding used (if applicable: researcher who coded food records for computer analysis and who assessed compliance was not blinded to subjects' diet allocation.

Intervention (if applicable):

subjects assessed by dietitian to categorize dietary regimen prior to study
subjects assigned to group according to computer-generated random numbers
same dietitian gave advice to all subjects and families
Dietary advice given to parents and children
- CHOx group
  - given a set number of carbohydrate exchanges for each meal and snack (15 g carbohydrates per exchange)
  - limit refined sugars
- LowGI group
  - eat regular meals and snacks of carbohydrate-containing foods in their preferred serving sizes to satisfy appetite
  - emphasis on consumption of at least one low-GI food per meal per day
  - moderate use of refined sugars

Statistical Analysis

sample size of 100 families allowed for a dropout rate of 15% and provided 80% power
intention-to-treat analysis performed on the assumption that subjects adhered to the dietary advice provided at entry to study
continuous variables were analyzed with the use of a two-sample t test
multiple linear regression used to adjust for confounding variables
categorical data anlyzewd by using either Pearson chi-square analysis or Fisher's exact test
Non-normal data were analyzed with Wilcoxon's rank-sum test and expressed as medians and ranges
For all of the GI quartile comparisons, P values were corrected with the use of Bonferroni's correction for multiple comparisons

Data Collection Summary:

Timing of Measurements:

3-day food record at 1, 3, 6, and 12 months

Dependent Variables

dietary intake
- energy, below, above, or within range, based on basal metabolic rate calculated using Schofield's equation
- protein
- fat
- fiber
- total carbohydrate
- total sugars
- sugars consumed for treatment of hypoglycemia or during exercise
- non-milk extrinsic sugars
- Glycemic index relative to glucose calculated by summing. Of 284 foods consumed, 194 were given known GI values and 90 were given estimated values based on composition
- carbohydrate distribution
comparison of dietary quality, food choice, and main sources of carbohydrate foods between the lowest and highest GI quartiles.

Independent Variables

Compliance to dietary advice
- families were encouraged not to change food intake pattern during days when food records were kept
- phone calls made 2 weeks before clinic visits to encourage completion of food records
- adherence to diet instruction assessed independently at each time point and categorized as
  - 1= exact adherence
  - 2=subject adhered generally to the advice givben and dietary intake was acceptable to diabetes management
  - 3=subject did not adhere to advice and intake was not acceptable for diabetes management
activity level

Control Variables

sugars used as part of diabetes management for hypoglycemia
underreporting of energy intake
dairy foods consumption

Description of Actual Data Sample:

Initial N: 104, 51% male in CHOX, 49% male in LowGI

Attrition (final N): 89, 14% dropout rate. Of the 15 dropouts, 11 dropped out from the CHOx group (4 did not follow the diet, 2 were too busy, 1 was noncompliant, 2 no longer attended the clinic, 1 had psychological problems, and 1 had an eating disorder) and 4 dropped out of the LowGI group (2 were too busy, 1 was noncompliant, 1 no longer attended clinic).

Age: mean 10 ±1.6 years

Ethnicity: not specified

Other relevant demographics:

duration of diabetes: 3.4 years for LowGI and 4.0 years for CHOx group
no significant difference in parents' marital status or socioeconomic status between groups

Anthropometrics: none specified

Location: Australia

Summary of Results:

The dropout rate in the CHOx group was significantly higher than in the LowGI group (P<.03).

Compliance (score of 1) was significantly higher in the LowGI group (P<0.001).

Energy Intake

A high proportion of subjects in both groups recorded energy intakes lower than their usual intakes, but there was no significant difference between groups.

Macronutrients

No significant differences in any of the macronutrients measured between groups at 6 and 12 months. Data were reanalyzed excluding the subjects who underreported food intake, but the data remained unchanged.

Reported macronutrient intakes at 12 months:

	Full model analysis		Excluding underreporters
Macronutrient	CHOx group	LowGI group	CHOx group	LowGI group
Energy, MJ/d	7.91.9	8.51.7	9.11.7	9.31.4
Protein, % total energy	17.62.5	17.33.7	16.31.9	16.34.1
Fat, % total energy	33.55.6	34.26.7	35.35.4	36.26.3
Total carbohydrate, % total energy	48.85.4	48.66.5	48.35.2	47.76.2
Fiber, g/d	20.25.0	22.56.5	22.44.1	23.07.2

No significant differences in sugar intakes between groups.

Carbohydrate intake and distribition of meals and snacks through day: no significant differences

Average number of carbohydrate food choices per day was not significantly different between the CHOx and Low GI groups (P=0.10 at 12 months).

Dfferences between subjects in the lowest- and highest-GI quartiles

lowest GI quartile consumed less potato and white bread at 12 months and consumed more dairy-based foods and whole-grain breads
total sugar intake was significantly higher in the lowest GI quartile, but that was due to differences in dairy foods consumption. Sugar intake was not significantly different between groups when dairy food consumption was controlled (P=.99).

Author Conclusion:

Children with type 1 diabetes who were given flexible, low-GI dietary advice did not have lower dietary quality or more limited food choices than did children who received more traditional carbohydrate exchange advice.

Energy intakes were comparable with normative data when undereporters were excluded from analysis.

The high prevalence of underreporting (about half of food records) the dietary data may be unreliable, but this criticism plagues all dietary assessment studies.

Flexible dietary instruction with emphasis on the use of low-GI foods resulted in improvements in glycemic control as well as quality of life in these subjects.

Funding Source:

Reviewer Comments:

Measures of blood glucose control were not reported in this study. LowGI was easier to follow given the dropouts from the CHOx group and the compliance.

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?	Yes
	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?	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.)	No
	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?	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?	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)?	Yes
	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?	Yes
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