EAL

Diabetes and Carbohydrates

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To predict the glycemic response to five mixed meals in noninsulin-dependent diabetic volunteers.

Inclusion Criteria:

Classification of type 2 diabetes mellitus on the basis of fasting plasma C-peptide >0.6 ng/ml.

Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

Recruitment: not specified

Study design:

Nonrandomized Clinical Trial.

Blinding: not specified

Intervention

1. Subjects instructed to consume the same evening meal the night before consuming the experimental meal.

2. 5 test meals were consumed in random order and consisted of 50% carbohydrates, 30% fat, and 20% protein. The experimental food (instant potato, white bread, rice, spaghetti, lentils and barley) contributed ~1/3 of total calories for the meal.

Statistical analysis:

The area under the glycemic response curve was calculated geometrically.
Mean areas under the glycemic curve were compared by Fisher's test after demonstration of significant heterogeneity by two-way analysis of variance.
Expected meal GIs were compared with observed mean incremental glycemic responses by linear regression analysis.

Data Collection Summary:

Timing of Measurements: Blood samples taken by finger prick before and 3-hr after each experimental meal.

Dependent Variable:

Glucose estimation and mean areas under the glycemic response curve

Independent Variables:

1/3 of the calories for each meal consisted of one of these sources: instant potato, white bread, rice, pasta, lentils and barley.
Meals were 600 calories each, about 42% of daily energy intake, 50% carbohydrate, 30% fat, 20% protein

Control Variables: not specified

Description of Actual Data Sample:

Initial N: 6 subjects, 5 female, 1 male

Final N: 6 subjects

Age: mean 59±7 SEM

Ethnicity: not specified

Other relevant demographics: duration of diabetes 9±2.7 yr

Anthropometry: BMI 25.2±1.9

Location: Canada

Summary of Results:

The estimated meal glycemic indexes were:

Instant potato 96.5
White bread 86.4
Rice 75.7
Spaghetti 64.9
Barley and lentils 46.6

The incremental glucose areas (Mmol/L/min, mean ± SEM) were:

instant potatoes 1281±200
white bread 1117±188
rice 947±158
spaghetti 713±123
barley and lentils 563±144

The response to the potato meal was significantly greater than to the rice, spaghetti, or barley-lentil meals (P<0.01).

The response to white bread was significantly greater than to spaghetti (P<0.05) and barley-lentil meals (P<0.01); the response to rice was significantly greater than to spaghetti (P<0.05) and barley-lentil meals (P<0.01).

The correlation between incremental blood glucose area and calculated meal GI for the five test meals was r=.9875 (P<0.01)

Author Conclusion:

The results of this study demonstrate the relative glycemic effects of mixed meals can be predicted from the glycemic index of the individual carbohydrate components.

These results stress the importance of type of carbohydrate in regulating blood glucose levels and support the use of the glycemic index in planning diabetic diets aimed at improving blood glucose control.

Funding Source:

Government:

Natural Sciences and Engineering Research Council

Reviewer Comments:

The results of this study are consistent with other studies evaluating the glycemic index of individual foods.

One would expect instant potato flakes to have a higher glycemic index than fresh potatoes.

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?	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?		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?		Yes
	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.)	Yes
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	Yes
	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)?	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?	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