EAL

GDM: Carbohydrate (2001)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To evaluate simultaneously the effects of 2 levels of dietary fiber and 2 soluble-insoluble fiber ratios of test meals on the post-prandial glycemic and lipemic responses of hypertriglyceridemic patients with type 2 diabetes.

Inclusion Criteria:

type 2 diabetes
mild hypertriglyceridemia ( TG between 2.4 and 4.1 mmol/l)
not on insulin or oral hypoglycemic agents for <=2 months.

Exclusion Criteria:

alcohol consumption on the day preceding the study

Description of Study Protocol:

Recruitment: not specified

Design: Randomized Controlled Trial

Intervention:

4 study breakfasts consisted of different amounts of fiber (10 or 20 g) with a ratio of soluble:insoluble fiber ratio of 1:4 or 2:3.
Fiber sources: oat bran, wheat bran, raisins and white flour.
Breakfast consisted of 2 muffins that incorporated the fiber, plus stewed rhubarb
All test meals made with the same ingredients but in different proportions

Blinding: not specified whether subjects knew what diet they were receiving

Statistical Analysis

all data were analyzed according to a 2 x 2 factorial design to detect the main effects and interactions of fiber level and soluble:insoluble fiber ratio.
first, results were submitted to a multiple analysis of variance
the incremental area under the curve for glucose, insulin, and triglyceride were calculated by the trapezium formula, then ANOVA was made on these results
mean and standard error of the mean was calculated for each test meal for all parameters

Data Collection Summary:

Timing of Measurements

On four occasions, each separated by at least one week, subjects came after an overnight fast to the Diabetes Research Unit to take one of the test meals according to a random sequience. Blood samples were collected before the meal and at intervals for 4 hours after the meal. Fasting blood samples taken at 15, 30, 45, 60, 75, 90, 120, 150, 180, and 210 minutes after the test breakfast.

Dependent Variables:

Incremental response of

plasma glucose, by glucose-6-phosphate-dehydrogenase method
plasma insulin, by radioimmunoassay
TG, T-cholesterol, HDL-cholesterol, by enzymatic colorimetric methods

Independent Variables:

4 test breakfasts
grams of fiber in test meals: 10g or 20g
soluble:insoluble fiber ratio of 1:4 or 2:3

Control Variables

Description of Actual Data Sample:

Initial N: 8 (7 men and 1 woman)

Final N: 8, but some lipid metabolism measures were missing and couldn't be included in MANOVA analysis

Age: 46-62 years; mean age 54.3±6.7

Ethnicity: not specified

Other relevant demographic factors: all but one subject treated with both diet and hypoglycemic agents; one treated by diet alone

Anthropometrics: BMI 23-36; mean BMI: 29.6±4.1

Location: Quebec, Canada

Summary of Results:

All subjects maintained their weights and test meals were well tolerated.

The incremental area under the curve for glucose and insulin was lower after consuming 20 g compared to 10-g dietary fiber (P<0.05), but was not affected by the ratio of soluble:insoluble fiber. The decrease in area was 31% for glucose and 13% for insulin.

The incremental area under the curve was similar for triglycerides, total cholesterol and HDL-cholesterol, regardless of the amount of fiber or ratio of soluble:insoluble fiber.

Author Conclusion:

The proportion of soluble to insoluble fiber in cereal and fruit does not necessarily predict the effect of fiber on the glycemic response, while the overall quantity of fiber does appear to affect postprandial glucose metabolism in Type 2 diabetes mellitus.

Funding Source:

University/Hospital:

Universite Laval (ste-Foy Quebec Canada)

Reviewer Comments:

Small sample size and study sample primarily elderly men. Similar studies need to be repeated in women and younger subjects.

Small sample size with diversity in ages and BMIs. Not many details given about the subjects.

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?	No
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?	Yes
	2.2.	Were criteria applied equally to all study groups?	N/A
	2.3.	Were health, demographics, and other characteristics of subjects described?	No
	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?		???
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	???
	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.)	???
	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?	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?		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?	No
	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)?	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