EAL

DM: Carbohydrates (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To examine the effects of a low-GI breakfast on both glucose and lipid metabolism in men with type 2 diabetes.

To evaluate the effects of a low-GI breakfast on hyperlipidemia at a subsequent lunch.

To determine the expression of some lipid-related enzymes: cholesterylester transfer protein (CETP), leptin, and peroxisome proliferator-activated receptor gamma.

Inclusion Criteria:

diagnosis of type 2 diabetes
fasting plasma glucose of 7.7 to 13.0 mmol/l
HbA1c 6.5-11%
plasma triglycerides less than 3 mmol/l

Exclusion Criteria:

female gender
abnormal renal, hepatic, or thyroid function
GI disorders

Description of Study Protocol:

Recruitment : subjects recruited from hospital outpatient clinic; patients had been seen for at least 6 months at the clinic.

Design

4-week run-in period where subjects attended group counseling sessions and had an individual counseling session with a dietitian. During this period the subjects were asked to follow their usual diet more strictly (55% CHO, 15% protein, 30% fat)
4-week double-blinded intervention period during which subjects were randomly allocated to receive a low-GI or a high-GI breakfast every day
15-day washout period during which subjects ate their usual diet
4-week intervention period where subjects received alternate diet

Blinding used (if applicable): authors claim the design was double-blind, however breakfasts differed in appearance (e.g. whole grain cereal vs. muesli, whole wheat bread vs. pumpernickel)

Intervention (if applicable)

high GI breakfast: whole wheat cereal, whole wheat bread, butter, milk;GI value 64.
low GI breakfast: cereal based on extruded oat bran concentrate, apple and fructose, pumpernickel bread, butter, milk; GI value 40. Cereal contributed 3g beta-glucans.

Statistical Analysis

for continuous variables with normal distribution a multiple analysis of variance followed by a post hoc test (LSD) was used
the mean value at the end of each diet minus the baseline value before each diet was used as the basis of a test of different carryover effects between the 2 diets.
for continuous variables with normal distribution, a test for different carryoever effects at the 10% level was used. If the test was not significant, a t test for different treatment effects at the 5% level was used
If the carryover test was significant, only data from the first dietary period was used in comparisons of treatment effects
if the usual assumption for the t test did not hold or if the data were on an ordinal scale, the Mann-Whitney U test replaced the t test.

Data Collection Summary:

Timing of Measurements; One-day metabolic profile: at the beginning and end of each diet period, subjects were hospitalized from 7:30 AM to 4:00 PM after an overnight fast. During this time

a sample of abdominal subcutaneous adipose tissue was obtained by needle biopsy
blood samples were collected at time 0 and then hourly during the 7 hours of the profile
at time 0 HbA1c, HDL and apo A1 were measured

Dependent Variables

plasma glucose, by glucose oxidase method
plasma insulin, by radioimmunoassay
plasma lipids
HbA1c
apoprotein A1, using immunochemical assay with Behring kits

Independent Variables

high or low GI breakfast, compliance assessed by food diaries
physical activity assessed by recall questionnaire

Control Variables

time
order

Description of Actual Data Sample:

Initial N:13 men

Attrition (final N): 13

Age: 59±2 y

Ethnicity: not specified

Other relevant demographics:

HbA1c 8.3±0.4%
fasting blood glucose 10.8±0.8 mmol/l

Anthropometrics:

bodyweight 82±3 kg
BMI 28±1

Location: France

Summary of Results:

Glycemic response

Fasting plasma glucose, insulin, and HbA1c were not affected by the chronic changes in the type of breakfast.
With the high-GI breakfast plasma glucose increased more rapidly to give high peaks in the beginning (baseline data, high-GIB v low-GIB, P<.001) and at the end (4 weeks, P<.001).
The area under the glucose curve after breakfast was significantly greater for the high-GIB than after the low-GIB at the beginning and the end of the nutritional period (P<0.10).
There was no significant difference in plasma glucose and insulin excursions after lunch during the 2 nutritional periods.

Blood lipids

4-week consumption of the low-GI diet induced a 10% decrease in fasting total cholesterol (P<.03)
The changes in the incremental area under the plasma total and free cholesterol response curves during the 7-hour profile day were also lower (P<.02 and <.04, respectively) after the period with the low-GIB than after the high GIB.
There was no significant difference in the fasting levels or the area under the curves for triacylglycerols and free fatty acids after breakfasts.
apo B was found to be lower (P<.03) after 4 weeks of the low-GIB compared to the high-GIB.

Other Findings

Changing the GI of 1 meal per day was not sufficient to modulate genes implicated in lipid metabolism.

Author Conclusion:

Using cereals and breads of low-GI carbohydrates and with modest doses of soluble fibers would be of benefit to patients with type 2 diabetes.

Funding Source:

Reviewer Comments:

Many non-significant results, but no power calculation was completed for sample size.

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?	No
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?		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?	Yes
	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?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	Yes
	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?	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?		???
	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?	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?	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