EAL

DM: Glycemic Index (2014)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To compare the effect of dietary education incorporating information about the glycemic index of carbohydrate against standard dietary advice.

Inclusion Criteria:

Newly diagnosed patients with type 2 diabetes (non-insulin dependent) referred to the clinic over an 18 month period were considered for inclusion.

Exclusion Criteria:

Pregnant or lactating women
Subjects aged > 70 years
Patients with other endocrine or lipid disorders
Those that had received dietary advice in the past
Patients judged to need oral hypoglycemic or insulin therapy
Patients where a language barrier made instruction difficult

Description of Study Protocol:

Recruitment

Newly diagnosed patients with type 2 diabetes (non-insulin dependent) referred to the clinic over an 18 month period were considered for inclusion.

Design

Randomized Controlled Trial. Each was randomly assigned to 1 of 2 groups using random number tables.

Blinding used (if applicable)

Not possible.

Intervention (if applicable)

Subjects received either standard dietary advice based on British Diabetic Association recommendations or standard dietary advice with emphasis on low glycemic index foods for 12 weeks.

Statistical Analysis

Comparison within groups were by paired Student's t test and between groups by Student's t tests. Correlations were made using Pearson correlation coefficient to examine the relationship between nutrients and glycemic control.

Data Collection Summary:

Timing of Measurements

Study ran for 12 weeks with review at 0, 4 and 12 weeks, with the only treatment being the dietary advice.

Dependent Variables

Dietary analysis of 3-day diet diaries, completed by 36 subjects
Fasting blood glucose
Fructosamine
Total, LDL and HDL cholesterol
Triglycerides

Independent Variables

Either standard dietary advice based on British Diabetic Association recommendations or standard dietary advice with emphasis on low glycemic index foods for 12 weeks.

Control Variables

Description of Actual Data Sample:

Initial N: 75 subjects met criteria, 60 agreed to participate

Attrition (final N): 51 subjects with type 2 diabetes. 9 failed to attend the final appointment. 26 subjects in standard advice group: 20 males, 6 females. 25 subjects in low GI group: 16 males, 9 females.

Age: Standard advice group: mean age 56 +/- 3 years, low GI group: mean age 54 +/- 2 years.

Ethnicity: not mentioned.

Other relevant demographics:

Anthropometrics: There were no significant differences between groups.

Location: London

Summary of Results:

	Standard Group Baseline	Standard Group End	Low GI Group Baseline	Low GI Group End
Fasting blood glucose (mmol/l)	11/1 +/- 0.7	9.8 +/- 0.6	12.2 +/- 0.7	9.6 +/- 0.6, p < 0.05
Fructosamine (mmol/l)	3.6 +/- 0.2	3.6 +/- 0.2, p < 0.05	3.8 +/- 0.2	3.2 +/- 0.2, p < 0.05
Cholesterol (mmol/l)	5.6 +/- 0.2	5.3 +/- 0.1, p < 0.05	6.2 +/- 0.3	5.5 +/- 0.3, p < 0.05
Triglyceride (mmol/l)	2.5 +/- 0.4	2.1 +/- 0.2	1.9 +/- 0.2	1.4 +/- 0.2, p < 0.05
LDL (mmol/l)	3.4 +/- 0.2	3.3 +/- 0.2	4.4 +/- 0.3	3.7 +/- 0.2
HDL (mmol/l)	1.0 +/- 0.06	1.1 +/- 0.12	1.2 +/- 0.04	1.2 +/- 0.06

Other Findings

Dietary analysis indicated that the group who received low glycemic advice not only had a significantly lower calculated mean diet glycemic index intake (77 +/- 1.1 vs 82 +/- 1%, p < 0.01) but also had a lower fat intake (25 +/- 1 vs 32 +/- 2% of total energy/day, p < 0.001), a higher carbohydrate intake (49 +/- 2% vs 44 +/- 1% of total energy/day, p < 0.05), and non-starch polysaccharide intake (21 +/- 1.5 vs 14 +/- 1 g, p < 0.001).

There was a significantly greater within-group fall in fructosamine (3.8 +/- 0.2 to 3.2 +/- 0.2 mmol vs 3.6 +/- 0.2 to 3.6 +/- 0.3 mmol, p < 0.05) and cholesterol (6.1 +/- 0.3 to 5.4 +/- 0.3 mmol vs 5.6 +/- 0.2 to 5.3 +/- 0.1 mmol, p < 0.05) in the low glycemic index group.

A significant correlation was detected between the glycemic index of the diet and the fall in fructosamine (r = 0.54, p < 0.01) and fasting blood glucose (r = 0.41, p < 0.05) which could not be demonstrated with the changes in fat or non-starch polysaccharides content of the diet, irrespective of the original study group, suggesting an independent role of the change in glycemic index of the carbohydrate in the diet.

Author Conclusion:

We have demonstrated that when patients with type 2 diabetes controlled by diet are given advice about low glycemic index carbohydrate, they are able to decrease the glycemic index of the food they eat. It appears that advice to reduce glycemic index of dietary carbohydrate leads to beneficial changes in other dietary constituents which could enhance the effect of the low glycemic index foods per se. The observed correlation between reported glycemic index of the diet and fructosamine would suggest that the drop in glycemic index is playing a role in the improved metabolic control.

Funding Source:

Not-for-profit

Foundation associated with industry:

Reviewer Comments:

Findings may be statistically relevant but not as clinically relevant. Not all subjects completed diet diaries, but other outcomes were measured.

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?		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?	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?	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?	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