EAL

DM: Carbohydrates (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To study effects of variation in carbohydrate content of diet on glycemia and plasma lipoproteins in patients with non-insulin-dependent diabetes mellitus.

Inclusion Criteria:

1. type 2 diabetes mellitus

2. treated with glipizide

3. changes in the dose of glipizide was made >1 month prior to the study.

Exclusion Criteria:

None specified.

Description of Study Protocol:

Recruitment: not specified

Study design: A 4- center randomized crossover trial

Intervention:

Subjects were randomized in blocks of 10 with 5 on each study diet for a period of 6 wks, followed by a cross over to the other study diet. 21 subjects continued the study diet for 8 additional wks.

Blinding Used (if applicable): not specified

Statistical analysis:

Repeated measures analysis of variance was used to compare the study diets, to assess the effect of diet order in which patients received the diets, and to assess the effect of site of study participation
Areas under the curve for plasma TG, glucose, and insulin were calculated using the trapezoidal rule and were compared using repreated-measures analysis of variance with site and order as grouping factors
24-hour profiles were comared using analysis of variance models and data at each time point were compared using the two-tailed paired t test without adjustment for mulitiple testing.

Data Collection Summary:

Timing of Measurements

Baseline evaluation: history and physical exam, and biochemical analyses (fasting plasma glucose and fasting TG).
During the last 3 days of each study period the subjects were admitted to the metabolic unit for fasting blood work and on the last day, blood was draw every 2 hr for glucose, insulin and TG.

Dependent Variables:

fasting plasma glucose
serum lipids and insulin
HbA1C
24-hour plasma glucose, insulin, and TG

Independent Variables

Rd monitored diet compliance by interviewing subjects
Subjects returned unconsumed food to the clinic
Daily energy intake for weight maintenance was determined by Harris-Benedict equation
Study diets:
- a. high carbohydrate: 55% carbohydrate and 30% fat; 15 g fiber per 4.2 MJ
- b. high MUFA diet provided 45% energy as fat and 40% as carbohydrates; 11 g fiber per 4.2 MJ.

Control Variables

Age
Race
BMI
Sex

Description of Actual Data Sample:

Initial N: 42, 33 men and 9 women

Final N: 42; incomplete results from 2

Age: 35-78, mean 58 ± 10

Ethnicity: 31 white, 4 Hispanic, 6 African-American, 1 Asian

Other Demograpics:

fasting Plasma Glucose: 5.6-11.1 mmol/l
triglycerides: 0.61-4.97 mmol/l

Anthropometrics: BMI 23-33, mean 28.2 ± 2.9

Location: Texas, California, Minnesota

Summary of Results:

Compliance to both study diets was excellent. The site of the study as well as the diet order did not affect results.

	High-carb diet, week 6	High MUFA diet, week 6	P, ANOVA
plasma cholesterol, mmol/l	5.07±0.91	4.97±0.93	.10
plasma triglycerides, mmol/l	21.9±0.85	1.75±0.70	<.0001
VLDL, mmol/l	0.80±0.36	0.65±0.28	.0001
LDL, mmol/l	3.36±0.70	3.36±0.78	.94
HDL, mmol/l	0.92±0.24	0.96±0.27	.27

*N=13 **N=8

Compared with the high MUFA diet, the high carbohydrate diet resulted in higher fasting TG and higher VLDL cholesterol by 24% (P<0.0001) and 23% (P=0.0001) respectively and increased daylong plasma TG, glucose, and insulin values by 10% (P=0.03), 12% (P<0.0001) and 9% (P<0.02) respectively.

The effects of both diets continued during the 14 wks that subjects consumed the study diets.

Author Conclusion:

In patients with type 2 diabetes mellitus, high carbohydrate diets compared with high MUFA diets, caused persistent deterioration of glycemic control and accentuation of hyperinsulinemia, as well as increased plasma TG and VLDL that may be undesirable and promote atherosclerosis.

Funding Source:

Government:

Dept. of Veterans Affairs, NIH

Industry:

Pfizer

Pharmaceutical/Dietary Supplement Company:

Reviewer Comments:

The study diets were well controlled and compliance to the study diets was high. This study needs to be repeated in free-living individuals.

Six weeks is probably too short a time period to demonstrate a change in LDL-cholesterol.

Even though subjects were on oral hypoglycemic agents some had higher fasting plasma glucose levels than considered desirable.

When counseling patients to use MUFA to replace carbohydrate, the RD needs to caution patients about the calorie density of food sources of MUFA and monitoring portion sizes to avoid weight gain.

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?	???
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?		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%.)	N/A
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	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?	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?	No
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