EAL

DM: Carbohydrates (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To evaluate in type 1 diabetic patients the long-term feasibility of a high-fiber diet composed exclusively of natural foodstuffs easily available in ordinary grocery stores and to determine the efficacy of such a diet in relation to blood glucose control and rate of hypolglycemic events.

Inclusion Criteria:

1. Type 1 diabetes melliltus

2. Treated with insulin

3. HbA1c >7 and <10%

Exclusion Criteria:

1. Renal failure

2. Liver disease

3. Symptomatic cardiovascular disease.

Description of Study Protocol:

Recruitment: unselected patients recruited consecutively from all patients referred to a diabetic clinic

Study design: Randomized Controlled Trial.

Intervention:

Study was randomized with 2 parallel groups, method of randomization not specified. Subjects followed usual diet for 4 wk and then randomized to high fiber (HF)(n=32) or low fiber (LF)(n=31). Using self-glucose monitoring, food records and records of hypoglycemic episodes, insulin was adjusted during this pre-trial period.

Blinding Used (if applicable): none mentioned

Statistical Analysis

differences between the two dietary treatments were analyzed by covariance analysis
Pearson's chi-square test used to check differences in side effects between groups
sample size based on calculations to give a power of 80%

Data Collection Summary:

Timing of Measurements: Lab data collected via blood draws in outpatient clinic after 4 wk of usual diet and after consuming study diet

Dependent Variables

Mean daily blood glucose, as the average of all five blood glucose measurements performed at the outpatient clinic on the last day of the treatment period
plasma glucose, cholesterol, HDL, and triglycerides
Number of hypoglycemic events, defined as blood glucose <0.3 mmol/l measured by reflectometer
Daily self-monitoring: fasting, 2-hr post breakfast, before and 2 and 4-hr post lunch.

Independent Variables

fiber content of diet
7-day food records self-recorded each month as used to assess compliance: unsatisfactory compliance defined as carbohydrate intake less than 45% of calories for either diet and/or consumption of fiber >20 g/day for the LF diet and >30g/day for the HF diet.
Study diet: 20% protein, 30% fat (8% SF, 20% MUFA, 2% PUFA), 50% carbohydrate (20% monosaccharides), 226 mg cholesterol. Calorie levels to maintain weight. A standard study diet was prepared in the outpatient clinic and served to patients on the day the blood glucose profile was measured on the metabolic ward.
High fiber diet (HF): 50 g dietary fiber, 70% GI. Emphasis on water-soluble fiber. Patients were advised to consumer one serving of legumes, 3 servings of high-fiber fruits, and 2 servings of high-fiber vegetables each day.
Low-fiber diet (LF): 15 g dietary fiber, 90% GI. Patients were advised to limit legume consumption to once per week, and to consume preferentially low-fiber fruits and vegetables.
Nutrition counseling: diet history, 2, 1-hr sessions with an RD, and monthly follow-up sessions with the RD for the 24 wks of dietary treatment. At each counseling session, the subjects provided 7-day food records that were used for nutrition counseling.

Control Variables

treatment with acarbose

Description of Actual Data Sample:

Initial N: 63 subjects

Final N: 46 considered compliant to diet (27% dropout rate); 24 in HF group (10 males, 14 females), 22 in LF group (7 males, 15 females)

91% of subjects in HF group completed the study (3 dropouts; plus 5 excluded for low fiber intake)
81% of subjects in the LF group completed the study (5 dropouts; plus 3 excluded for high fiber intake)

Age: 28±9 yr

Ethnicity: not specified

Other relevant demographics: duration of diabetes 10±6 yr, mean BMI 24 ±0.6

Anthropomerics: Both groups were comparable on baseline values, using intent-to-treat analysis

Location: Italy

Summary of Results:

The number of subjects on acarbose in both groups was similar (45% HF vs. 48% LF).

	Intention to Treat		Compliant to Diet
	HF, % change	LF, % change	HF, % change	LF, % change
HbA1C , %	0	+3.4	-2.0*	+5.8
Mean daily plasma glucose, mmol/l	-9.0*	-6.5	-15.0**	+14.7

*P<0.01; **P<0.05

Those consuming the HF diet compared to the LF diet had significantly fewer hypoglycemic episodes: 0.8±0.7 vs. 1.7±1.2/patient/month (P<0.05).

56% of patients on HF diet had minor GI side effects (flatulence, diarrhea) compared to 40% on LF diet (NS).

87% of those on the HF diet + acarbose had GI side effects (P<0.05)

Author Conclusion:

Adult type 1 diabetic patients are able to comply with a long-term dietary treatment based on a HF/low GI diet in >70% of cases with a significant and long-lasting improvement in plasma glucose control without major drawbacks.

Funding Source:

Government:

italian national research council

Industry:

Bayer (Italy)

Pharmaceutical/Dietary Supplement Company:

Reviewer Comments:

27% dropout rate based on compliant subjects.

The mean blood glucose and HbA1c in this study were quite high and above desirable ranges.

The number of RD visits during this study was 2 sessions (60 minutes each) within the first month and monthly sessions for 6 months of the study or 8 sessions over 6 months.

The high fiber fruits were:

Apple, oranges, pears, tangerines

High fiber vegetables were:

Artichokes, eggplants, mushrooms, broccoli

Low fiber fruits:

Banana, fruit juice

Low fiber vegetables:

Tomatoes, lettuce, red cabbage, peppers.

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?		???
	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.)	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?		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