EAL

Mediterranean Diet and the Prevention and Treatment of CVD

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To explore the relation between adiponectin concentrations and consumption of a Mediterranean-type diet before and after adjustment for age, total energy intake, BMI, waist circumference, and other potential confounders in adult diabetic women.

Inclusion Criteria:

participant in Nurse's Health Study (NHS)
female
age 30-55y
blood sample obtained in Nurse's Health Study and adiponectin value present
free of coronary heart disease, myocardial infarction, CABG, PTCA and stroke at the time of the blood draw in 1990

Exclusion Criteria:

Excluded if not included above.

Description of Study Protocol:

Recruitment: 1188 of the 121,700 subjects in the Nurses' Health Study had a confirmed diagnosis of type 2 diabetes. This analysis included 987 of these women who met the inclusion criteria for the study.

Design: this study is a new cross-sectional analysis of data from the NHS

Blinding used (if applicable) -Not applicable

Intervention (if applicable)-Not applicable

Statistical Analysis

comparisons of descriptive measures were conducted by using linear regresssion to test for trend across Mediterranean dietary pattern score groups for continuous variables
reported correlations calculated using Spearman's nonparametric analysis
associations between a Mediterranean-type diet and plasma adiponectin concentrations were evaluated using simple linear regression models for crude analysis and multiple regression for adjusted analyses, with logarithmic transformation of plasma adiponectin concentration values to achieve normal distribution

Data Collection Summary:

Timing of Measurements

dietary assessments obtained biennially in NHS; this analysis used data from 1990
blood samples collected in 1989 or 1990 using kit supplied by NHS and returned for analysis within 24 hours of draw.

Dependent Variables

adiponectin, assessed by radioimmunoassay

Independent Variables

Dietary intake was assessed by using a semi-quantitative food frequency questionnaire with an assessed reliability and validity.
women were asked how often on average over the previous year they had consumed a specified amount of the food in question
9 response categories ranged from "never" to "6 or more times per day"
the dietary data from 1990 was analyzed cross-sectionally; data 1980, 1984, 1986, and 1990 was also used prospectively as a cumulative average
Mediterranean dietary pattern scores were determined by using a 9-point scale. If individual median intakes of fish, fruit, legumes, nuts, ratio of polyunsaturated to saturated fat, vegetable, or whole grain consumption were higher than the group median, a point was awarded. A point was also awarded if red meat intake was below the median value. A point was awarded if alcohol consumption was between 5 and 15g/day.

Control Variables

age
total energy intake
BMI
waist circumference; estimate used for 39% of women, for whom data was missing
smoking status
physical activity in METS
self-reported chronic disease status
socioeconomic variables
medication use
fiber intake
underreporting of food intake

Description of Actual Data Sample:

Initial N: 987 women

Attrition (final N): 987

Age: 58.8±6.6

Ethnicity: 76% white

Other relevant demographics: 19% taking insulin; mean HbA1c 6.9±1.8%

Anthropometrics

BMI 30.0 ±6.3
waist circumference 90.5±14.5

Location: United States

Summary of Results:

Mediterranean Diet Scores

Women with the higher scores (6 to 9) tended to be older; have lower BMI, waist circumference, and triacylglycerols; had higher energy intakes, levels of physical activity, HDL, and plasma adiponectin compared to women who scored 3 or below on the diet scale.
No significant difference between among the Mediterranean diet groups with respect to WHR, socioeconomic variables, hypertensive status, total and LDL cholesterol, HbA1c, or use of reported medications.

Dietary intakes of diabetic women according to Mediterranean dietary pattern score

Diet components	Mediterranean dietary pattern score				P
	Total	0-3	4-5	6-9
Alcohol, g/d	3.7±7.8	3.5±8.3	3.5±7.4	4.6±8.0	<0.01
Fish, servings/d	0.3±0.2	0.2±0.1	0.3±0.2	0.5±0.3	<0.01
Fruit, servings/d	2.5±1.2	1.8±0.9	2.7±1.1	3.4±1.1	<0.01
Legumes, servings/d	0.4±0.2	0.3±0.2	0.5±0.2	0.6±0.3	<0.01
Nuts/servings/d	0.3±0.4	0.2±0.3	0.3±0.3	0.4±0.5	<0.01
PUFA:SFA	1.1±0.6	1.1±0.5	1.1±0.6	0.9±0.5	<0.01
Red meats, servings/d	0.5±0.1	0.4±0.1	0.5±0.1	0.6±0.1	<0.01
Vegetables, servings/d	2.9±1.4	2.0±0.9	3.2±1.1	4.0±1.7	<0.01
Whole grains, servings/d	1.3±0.9	0.8±0.7	1.3±0.9	2.1±1.0	<0.01
Total fiber, g/d	19.8±6.5	15.2±4.0	20.8±5.3	26.4±7.0	<0.01
Cereal fiber, g/d	4.5±2.1	3.5±1.6	4.6±1.9	6.0±2.5	<0.01
Fruit fiber, g/d	4.7±2.5	3.3±1.8	5.0±2.3	6.7±2.7	<0.01
Vegetable fiber, g/d	6.6±2.6	4.8±1.6	7.1±2.1	8.9±3.1	<0.01

Adiponectin concentrations and diet components

No significant trends were detected between adiponectin and servings/day of fish, legumes, PUFA:SFA, red meat or vegetable consumption independently.
Macronutrient intake was not associated with adiponectin
The relation between diet score and adiponectin did not differ appreciably across varying levels of energy intake, body weight, or exercise or by smoking status

Adiponectin concentrations in diabetic women by quintile of selected Mediterranean dietary pattern score component

Dietary component	Quintile of Food Intake
	1	2	3	4	5	P for trend
Alcohol
Age- and energy-adjusted adiponectin, microgram/mL	5.74±1.04^a	5.38±1.04	6.25±1.07	6.52±1.11	6.81±1.15	0.03
Multivariate-adjusted adiponectin, (microgram/mL)^b	5.37±1.05	4.92±1.04	6.25±1.07	5.97±1.11	6.03±1.15	0.10
Fruit
Age- and energy-adjusted adiponectin, microgram/mL	5.11±1.05	5.43±1.05	6.27±1.05	5.53±1.06	6.22±1.06	0.02
Multivariate-adjusted adiponectin, (microgram/mL)^b	4.88±1.06	5.28±1.06	5.78±1.06	4.88±1.06	5.38±1.06	0.50
Nuts
Age- and energy-adjusted adiponectin, microgram/mL	5.10±1.06	5.47±1.06	5.93±1.05	5.80±1.05	6.15±1.06	<0.01
Multivariate-adjusted adiponectin, (microgram/mL)^b	4.84±1.06	5.08±1.06	5.43±1.06	5.26±1.06	5.44±1.06	0.08
Whole Grains
Age- and energy-adjusted adiponectin, microgram/mL	5.15±1.05	5.39±1.05	5.46±1.06	5.90±1.05	6.71±1.06	<0.01
Multivariate-adjusted adiponectin, (microgram/mL)^b	4.92±1.05	4.98±1.06	5.01±1.06	5.51±1.06	6.11±1.06	<0.01

^a median ±SE (all such values)

^b the multivariate model was adjusted for age, total energy intake, BMI, waist circumference, activity level, and smoking status

^cModel is calculated using the cumulative average of dietary data from 1980, 1984, 1986, and 1990

Author Conclusion:

Adherence to a Mediterranean-type diet was positively associated with plasma adiponectin concentrations in diabetic women with no history of heart disease
Anthropometric variables, lfestyle, and medical history did explain some of the observed association, but a trend toward adiponectin concentration in high adherers to the diet was still apparent
The association between the Mediterranean diet and adiponectin can be attributed mainly to intakes of alcohol, nuts, and whole grains.

Funding Source:

Reviewer Comments:

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)	N/A
	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?	N/A
	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.)	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?	Yes
	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?		N/A
	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.)	N/A
	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?		N/A
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	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?	N/A
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	N/A
	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?	N/A
	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?	N/A
	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)?	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?	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