EAL

DM: Carbohydrates (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To examine the intake of natural dietary fiber reported by outpatients enrolled in the EURODIAB IDDM Complications Study for possible relations with HbA_1c and prevalence of severe ketoacidosis or severe hypoglycemia.

Inclusion Criteria:

In each of 31 European centers, a random sample of individuals aged 15-60 years with type 1 diabetes was selected from defined strata in relation to gender, age, and diabetes duration (see Diabetologia 1994;37:278-285)

Exclusion Criteria:

See Diabetologia. 1994;37:278-285
For this study:
- Subjects from Bucharest (n=139) (because of extremely high prevalence of admission to hospital for ketosis compared to rest of centers)
- Subjects taking oral hypoglycemic agents (n=18)

Description of Study Protocol:

Recruitment

See Diabetologia. 1994;37:278-285

Design

Comparison of HbA_1c, severe ketoacidosis, and severe hypoglycemia with quartiles of total, soluble, and insoluble fiber intake in 2065 people with type 1 diabetes

Blinding used (if applicable)

None

Intervention (if applicable)

None

Statistical Analysis

Cochran-Mantel-Haenszel test to test for trend in confounding factors across quartiles
Analysis of variance for categorical and continuous variables to test for trend in confounding factors across quartiles
Least square regression to analyze associations between fiber intake and HbA_1c
Logistic regression to determine odds ratios for severe ketoacidosis and severe hypoglycemia in quartiles of fiber intake.

Data Collection Summary:

Timing of Measurements

One questionnaire

Dependent Variables

HbA_1c(enzyme immunoassay)
Severe ketoacidosis (self report - number of times in past year, requiring hospitalization)
Severe hypoglycemia (self report - number of times in past year, serious enough to require help of another person)

Independent Variables

Total fiber, soluble fiber, and insoluble fiber (3-day dietary record with soluble and insoluble fiber from European food lists). (NOTE: the nutritional assessment and analysis procedures are described in detail elsewhere, as is the EURODIAB nutrient database)

Control Variables

Physical activity (self report - vigorous exercise at least once a week)
Smoking habits (self report - current/ex-smoker)
Frequency of insulin injections
Number of daily insulin units injected/kg body weight
Alcohol intake

Description of Actual Data Sample:

Initial N: 3250 subjects with type 1 diabetes

Attrition (final N): 3250

Relation between fiber and HbA_1c: 2065 individuals (1051 men, 1014 women)
Relation between fiber and severe ketoacidosis or severe hypoglycemia: 2687 subjects (1366 men, 1321 women)

Age: 32 years ± 10.2

Ethnicity: not reported

Other relevant demographics:

Duration of diabetes: 14.8 yrs ± 9.5
Self reported alcohol intake
- none: 49.5%
- <20 g/d: 37.9%
- >20 g/d: 12.6
Frequent meals (> or = 6 times/d): 59.1%
Frequent insulin injections (> or = 3 times/d): 50.8%
Current smokers: 33.2%
Vigorous exercise at least once a week: 14%

Anthropometrics :

25.9% of subjects had a BMI > 25 kg/m²
Mean HbA_1c6.4 (1.9-15.5)

Location: 31 centers in Europe:

Southern European: Athens, Bari, Cagliari, Lisbon, Milan, Perugia, Pisz, Rome, Turin, Thessaloniki, Verona
Eastern European: Budapest, Krakow, Zagreb
North-western European: Cork, Dusseldorf, Gent, Helsinki, Leiden, London, Luxembourg, Manchester, Munich, Paris, Sheffield, Valenciennes, Vienna, Wolverhampton.

Summary of Results:

Total fiber intake (g/d): 17.7 (2.6-63.4) Quartiles: Median intake (range)	Soluble fiber intake (g/d): 5.6 (0.8-20.2) Quartiles Median intake (range)	Insoluble fiber intake (g/d):12.0 (1.8-43.8) Quartiles Median intake (range)
11.4 (2.6-13.6)	3.5 (0.8-4.3)	7.6 (1.8-9.1)
15.6 (13.6-17.7)	4.9 (4.3-5.6)	10.6 (9.2-12.0)
20.0 (17.7-22.8)	6.3 (5.6-7.2)	13.5 (12.0-15.5)
27.3(22.8-63.4)	8.9 (7.2-20.2)	18.7 (15.5-43.8)

Other Findings

1. Total energy intake (kcal): 22.89 (670-5510)

2. Carbohydrate intake (% of energy): 42.3±7.3

3. Total fiber intake (g/d) was inversely related to HbA_1c (p = 0.02), independently of carbohydrate intake, total energy intake, and other covariates regarding lifestyle and diabetes management (self-reported alcohol consumption, frequency of meals, BMI > 25 kg/m², frequency of insulin injections, use of human insulin, smoker, vigorous exercise at least once a week)

4. Soluble fiber significantly predicted HbA_1c levels (p=0.02) (multivariate stepwise regression)

4. Severe ketoacidosis risk fell significantly with higher fiber intake (p=0.002).

5. The occurrence of severe hypoglycemia was not related to fiber intake

6. Beneficial effects of fiber on HbA_1c and the risk of severe ketoacidosis were particularly pronounced in patients from southern European centers.

Author Conclusion:

This study shows that a higher fiber intake is independently related to a reduction in HbA_1c levels in European people with type 1 diabetes.
Increased fiber intake may reduce the risk of severe ketoacidosis
The above benefits have already been observed for fiber intakwe within the range commonly consumed by people with type 1 diabetes

Funding Source:

Reviewer Comments:

A strength of this study is taking the covariates into consideration in the model, as well as regional specifics
A lot of data based on self-report
Cross-sectional associations do not prove cause and effect relationships; however, they can provide guidance for future controlled clinical trials

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)	N/A
	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)	N/A

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?	???
	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)	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?	Yes
	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?		???
	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%.)	Yes
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	???
	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?	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.)	N/A
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	???
	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?		N/A
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	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?	N/A
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	N/A
	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?	N/A
	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?	N/A
	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?	N/A
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	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?		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?	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