EAL

GDM: Carbohydrate (2001)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine the plasma glucose and insulin response to a standard glucose meal in the absence and the presence of varing amounts of protein in mild type II diabetic subjects.

Inclusion Criteria:

1. Met National Diabetes Data Group criteria for diagnosis of type II diabetes

2. Subjects were on no medications to treat diabetes (insulin or oral hypoglycemics)

Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

Recruitment: not specified

Design: Three studies of 5-7 patients were described in this paper. Subjects were given 50g doses of glucose and/or protein and glucose and insulin responses were monitored.

Blinding Used (if applicable): not specified

Intervention (if applicable):

On diets consisting of 200 g carbohydrates/d and energy to meet needs for 3 days prior to studies.
Overnight fast (8-10 hr)
Study I: 7 subjects were given 50 g glucose or 50 g protein (236 g raw lean hamburger, served well-cooked) or 50 g glucose + 50 g protein for 3 days in random order.
Study II: 5 subjects were given 50 g glucose + 10, 30 or 50 g protein (47, 142, or 236 g raw weight of hamburger).
Study III: 5 subjects given either 2 doses of 50 g glucose 4 hr apart or 50 g glucose with 50 g protein 4 hr apart. Blood drawn before, ½, 1, 2, 3, 4, 5, 6, 7, and 8 hr after ingestion of the first test meal.

Statistical Analysis

mean ± SEM
Student's t test for paired variates used for analysis of statistical significance

Data Collection Summary:

Timing of Measurements: Indwelling catheter for blood collection; collection times at 0, ½, 1, 2, 3, 4, 5, 6, 7, and 8 hr after ingestion of the meal

Dependent Variables:

Plasma glucose, by glucose-oxidase method
insulin response, by radioimmunoassay

Independent Variables

50-g protein doses consisted of hamburger. Fat content determined by gravimetric analysis of several ether extractions of the meat
Study I: 7 subjects were given 50 g glucose or 50 g protein (236 g raw lean hamburger, served well-cooked) or 50 g glucose + 50 g protein for 3 days in random order.
Study II: 5 subjects were given 50 g glucose + 10, 30 or 50 g protein (47, 142, or 236 g raw weight of hamburger).
Study III: 5 subjects given either 2 doses of 50 g glucose 4 hr apart or 50 g glucose with 50 g protein 4 hr apart.

Control Variables: not specified

Description of Actual Data Sample:

Initial N: 9 males

Final N: 9

Age: 61±12 years (38-74 yr)

Ethnicity: not specified

Other Relevant Demographics: none specified

Anthropometrics:

Mean body weight: 123±23% DBW using 1959 Metropolitan Life Insurance Co. tables

Location: USA

Summary of Results:

The plasma glucose area above baseline following a glucose meal was reduced 34% when protein was given with glucose. (P<0.01)

The insulin area following glucose was only modestly greater than with a protein meal (97±35, 83±19 µU/hr/ml respectively).

When glucose was given with protein, the mean insulin area was considerably greater than when glucose or protein was given alone (247+33 µ U/hr/ml) (P<0.01).

The addition of 10 g or 30 g of protein to 50 g glucose did not affect the glucose curve. However, the addition of 50 g protein there was a significant reduction in serum glucose (P<0.05).

When subjects were given 50 g glucose or 50 g glucose + 50 g protein, as 2 meals, 4 hr apart, the insulin areas were not significantly different for each meal but were higher when protein + glucose was consumed.

After the second glucose meal, the plasma glucose area was 33% less than after the first meal. Following the second glucose + protein meal, the plasma glucose area was markedly reduced, being only 7% as large as after the first meal.

Author Conclusion:

Study results indicate that protein given with glucose will increase insulin secretion and reduce the plasma glucose rise in at least some people with type II diabetes.

Whether a moderately high protein diet will be beneficial to persons with type II diabetes remains to be determined. Nevertheless, the present studies suggest that protein ingestion is important in stimulating insulin secretion in these individuals. When carbohydrate is ingested, the simultaneous ingestion of protein may also prove useful in reducing the postmeal glucose rise. In addition, these data indicate the need to consider the insulin secretory response and a second and third meal effect on blood glucose concentrations when determining the glycemic response to a food.

Funding Source:

University/Hospital:

University of Minnesota

Reviewer Comments:

Nine subjects were included in the study, but only 5-7 were used for each of the three sub-studies described. No information was given to explain why some of the subjects were not used in all studies.

Presentation of the results could have been more clear; figures did not always indicate the level of significance.

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?		No
	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?	No
	2.4.	Were the subjects/patients a representative sample of the relevant population?	No
3.	Were study groups comparable?		???
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	No
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	???
	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?		???
	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%.)	???
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	No
	4.4.	Were reasons for withdrawals similar across groups?	???
	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.)	???
	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?	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?	No
	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)?	No
	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