Fiber

DF: Diabetes (2008)

Citation:

Karlstrom B, Vessby B, Asp NG, Ytterfors A. Effects of four meals with different kinds of dietary fibre on glucose metabolism in healthy subjects and non-insulin-dependent diabetic patients. Eur J Clin Nutr. 1988 Jun; 42 (6): 519-526.

PubMed ID: 2842146

Study Design:

Randomized crossover trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

NEUTRAL: See Quality Criteria Checklist below.

Research Purpose:

To investigate the effects of a change from a low-fiber meal to a meal with an increased content of dietary fiber among both healthy women and women with diabetes.

Inclusion Criteria:

Not described.

Exclusion Criteria:

Not described.

Description of Study Protocol:

Recruitment: Not described
Design: Control meal and three test meals were given in random order to each participant after an overnight fast. The test meals were separated by at least a day and not more than two test meals were eaten every week.
Blinding used: Not described, but objective outcome (biochemical measures).

Intervention

Meal A: Low-fiber (white bread, coffee, beef, potatoes, onion, tomatoes, parsley, margarine and apple juice)
Meal B: High-fiber cereals (crisp bread, whole-meal wheat bread, wheat bran, coffee, beef, potatoes, onion, tomatoes, parsley, margarine and apple juice)
Meal C: High-fiber from legumes (green beans, dried white beans, bouillon powder, coffee, beef, potatoes, onion, tomatoes, parsley, margarine and apple juice)
Meal D: High-fiber from (crisp bread, dried white beans, bouillon powder, coffee, beef, potatoes, onion, tomatoes, parsley, margarine and apple juice).

Statistical Analysis

Areas of deviation in the curve from fasting values over time (blood glucose and serum insulin)
ANOVA
- Models of blood glucose, insulin, lipids
  - Factors: Patient, meal, time point and meal x time-point interaction.
- Models of body weight, glucose and insulin areas of deviation
  - Factors: Group, patient (nested within group) and group x meal interaction.

Data Collection Summary:

Dependent Variables

Blood samples for glucose and insulin: Fasting, 20, 30, 60, 90, 120, 180 and 240 minutes after the meal
Basal glucose and insulin: Mean values of two measurements during fasting before the meals
Blood glucose: Measured by glucose oxidase method
Serum insulin: Measured by Phadesbas Insulin
TG and HDL: Measured 60 and 250 minutes post-meal, by enzymatic methods.

Independent Variables

Starch
Sucrose
Glucose
Fructose
Total fat
Fiber content.

Control Variables

N/A.

Description of Actual Data Sample:

Initial N: 12 healthy women, 13 women with diabetes
Attrition (final N): Not described.

Age

Healthy women: Mean, 63 years (range, 53 to 77 years)
Women with diabetes: Mean, 64 years (range, 54 to 70 years).

Ethnicity

Not reported.

Other Relevant Demographics

Eight women with diabetes treated with oral medication: Nine had diabetes for more than five years; two for more than one year; two for six months.

Anthropometrics

Healthy women: Mean BMI, 24.5 (SEM, 0.9)
Women with diabetes: Mean BMI, 25.7 (SEM, 1.1)

Location

Department of Geriatrics, Uppsala University, Sweden.

Summary of Results:

Food analysis results
- For meals A, B and D, the deviation between the sum of analyzed digestible carbohydrates plus fiber and the carbohydrate by difference was only 5% to 7%
- The leguminous meal (C) was 20% lower than expected, due to lower digestible carbohydrate content.
Blood glucose results
- In the healthy group, there were no significant differences between the control meal and the test meals or between the different test meals, with respect to blood glucose
- In the group with diabetes, the blood glucose was significantly lower after the leguminous and the mixed-fiber meal, compared with the control meal.
Insulin results
- In the healthy group, insulin response was lower after the leguminous meal than the control
- In the group with diabetes, the insulin response was reduced after all test meals, compared with the control meal. The insulin responses after the three test meals did not differ.
The content of digestible carbohydrate was lower in the high-fiber meals than the control meal
There were no differences in triglycerides, serum cholesterol or HDL cholesterol after the test meals, compared to control between test meals, either in the healthy or diabetic group
No differences in body weight or fasting insulin between the different days when the meals were eaten.

Author Conclusion:

NIDDM patients should be recommended diets with an increased content of dietary fiber.

Funding Source:

Government:

Swedish Medical Research Council

Not-for-profit

Foundation associated with industry:

Reviewer Comments:

Description of recruitment and inclusion and exclusion criteria not mentioned
Did not describe any dropouts; assumed no loss to follow-up
Statistical analysis unclear.

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?		???
	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?	No
	2.2.	Were criteria applied equally to all study groups?	N/A
	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?	???
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?	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?	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?	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?	Yes
	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?	???
	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)?	N/A
	8.6.	Was clinical significance as well as statistical significance reported?	N/A
	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