EAL

DM: Prevention and Treatment of CVD (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To compare the effects of a high-carbohydrate (CHO) diet and a high-monounsaturated fatty acid (MUFA) diet on LDL oxidative resistance in free-living individuals with type 2 diabetes mellitus.

Inclusion Criteria:

BMI <35
HbA1c <8.0%
serum cholesterol < 7.2 mmol/l
triglycerides < 3.0 mmol/l
treatment with diet or oral hypoglycemic agents
no intake of antioxidants vitamins or hypolipidemic drugs

Exclusion Criteria:

smoking
alcohol intake greater than 20 g/day
diagnosis of diabetic enteropathy, renal disease, thyroid disease, or drug-treated hypertension

Description of Study Protocol:

Recruitment : subjects recruited from outpatient lipid and diabetes clinics

Design:

6-week pre-inclusion period, during which individuals consumed their usual diet which is low in SFA and high in CHO
12-week diet intervention period with a crossover design

Blinding used (if applicable): not applicable

Intervention (if applicable)

subjects randomly assigned to CHO diet or MUFA diet using a compuer-generated random number table
both diets consisted of natural foods with limitation of red and processed meats, eggs, and whole-fat dairy products
diets were isocaloric and differed only in fat and carbohydrate content
diets:
- CHO: use of olive oil restricted to 10% of calories, cereal products, legume, and fruit consumption increased
- MUFA: olive oil approximately 25% of calories, recommendation to increase whole-grain bread to keep fiber content equal to CHO diet

Statistical Analysis

two-tailed t tests used to compare changes in outcome variables in response to dietary treatment and diet period and carryover effects for the two-period crossover design
differences between the CHO and MUFA diets were also tested by analysis of covariance using general linear models, with baseline values or sex as covariates
Pearson's correlation coefficients and stepwise multiple regression analysis were used to evaluate predictors of LDL susceptibiity to oxidation

Data Collection Summary:

Timing of Measurements:

anthropometric measurements and dietary assessment completed twice during the run-in period and every 2 weeks during the intervention period
blood extraction performed on week 6 of each diet

Dependent Variables

change in LDL resistance to oxidation
body weight
glycemic control
serum lipoproteins

Independent Variables

dietary intake, measured every 2 weeks with 3-day diet record
subjects instructed to maintain usual physical activity

Control Variables

Description of Actual Data Sample:

Initial N: 26, 13 men and 13 women

Attrition (final N): 22 (84% retention). 4 withdrawn due to poor dietary compliance.

Age: 61±7 years

Ethnicity: not specified

Other relevant demographics: diagnosis of diabetes for 5.3±2.0 years

Anthropometrics:

Location: Spain

Summary of Results:

Dietary Intake

Those on the MUFA diet had a lower fiber consumption than subjects on the CHO diet, but self-reported diets were in good agreement with the planned diet.
There were between-diet differences in comsummption of Vitamin C and other carotenoid intakes during the MUFA diet.

Values at baseline and after ingestion of two experimental diets for 6 weeks

Variables	Baseline	CHO diet	MUFA Diet	P-value
Weight, kg	80.2±16.0	78.1±14.0	77.8±13.9	>0.1
Fasting blood glucose, mmol/l	9.0±2.7	8.3±2.4	9.3±3.2	0.055
HbA1c	6.5±0.9	6.5±0.8	6.6±0.9	>0.1
Total cholesterol, mmol/l	5.49±1.01	5.60±1.17	5.45±1.11	>0.1
LDL, mmol/l	3.36±0.71	3.42±0.89	3.27±0.64	>0.1
HDL, mmol/l	1.21±0.37	1.32±0.27	1.28±0.28	>0.1
VLDL, mmol/l		0.65±0.45	0.42±0.28	0.023
Total triglycerides, mmol/l	2.02±0.81	2.09±1.58	2.12±0.98	>0.1
VLDL triglyceride, mmol/l		0.76±0.46	0.64±0.43	0.016
VLDL triglyceride/VLDL apoB		3.26±2.83	2.32±2.27	0.029
Rate of oxidation, nmol dienes/min per mg LDL protein		36.3±10.0	39.5±10.7	0.069
Amount of dienes, nmol/mg LDL protein		716±143	750±198	>0.1

Other Findings

The VLDL triglyceride to VLDL apolipoprotein B quotient was significantly lower during the MUFA diet, indicating lesser particle enrichment with triglycerides in comparison to the CHO diet.
the only correlate of change in LDL oxidizability from one diet to the other diet was vitamin E intake (r=0.457, P=0.043)

Author Conclusion:

The diets had similar effects on the resistance of LDL against oxidation.

Increasing dietary fat content from 28% of energy in the CHO diet to 40% of energy in the MUFA diet improved tastiness and acceptance, provided a similar degree of weight, glucose, and cholesterol control, and lowered VLDL lipids.

A MUFA-enriched diet is a good alternative ot high-CHO diets for medical nutrition therapy of diabetes.

Funding Source:

Reviewer Comments:

Energy intake was monitored and adjusted every 2 weeks to prevent excess calorie intake while on the MUFA diet. Power calculations done. No washout period between diets.

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?	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?	No
	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)?	No
	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?	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