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Citation:

Abiemo EE, Alonso A, Nettleton JA, Steffen LM, Bertoni AG, Jain A, Lutsey PL. Relationships of the Mediterranean dietary pattern with insulin resistance and diabetes incidence in the Multi-Ethnic Study of Atherosclerosis (MESA). Br J Nutr. 2012 Aug 30: 1-8.

Study Design:
Prospective Cohort Study
Class:
B - Click here for explanation of classification scheme.
NEUTRAL: See Research Design and Implementation Criteria Checklist below.
Research Purpose:

To assess the association between adherence to a Mediterranean diet  and risk of type 2 diabetes in a multi-ethnic population.

Inclusion Criteria:

Subjects free of type 2 diabetes and cardiovascular disease (CVD).

Exclusion Criteria:

Subjects with type 2 diabetes or cardiovascular disease.

Description of Study Protocol:

Study Description

Prospective cohort study to determine the relationship between adherence to a Mediterranean diet and risk of type 2 diabetes in the Multi-Ethnic Study of Atherosclerosis (MESA) cohort.

Study Duration

6.6 years.

Location

United States.

Data Collection Summary:

Dietary Assessment Method

127-item FFQ.

Brief Description of Dietary Patterns

MedDiet Score: Total score zero to 10:

  • The score included ten food components:
    • Vegetables (excluding potatoes)
    • Whole grains
    • Nuts
    • Legumes
    • Fruits
    • Ratio of MUFA:SFA
    • Red and processed meat
    • Whole-fat dairy products
    • Fish
    • Alcohol.
  • Participants with intakes above the median intake of traditional foods in the MedDiet (i.e., vegetables, whole grains, nuts, legumes, fruits, MUFA:SFA ratio, fish) received one point, while those below the median received zero points.
  • For potentially detrimental foods inversely associated with the MedDiet (i.e., red/processed meats, whole-fat dairy products), those with intakes below the median received one point; otherwise, they received zero points.

Outcomes Measured

Incidence of type 2 diabetes.

Methods of Outcome Assessment

Incident diabetes was defined as fasting blood glucose 7.0mmol per L or more (1,260mg per L), self-reported diabetes or using hypoglycemic drugs.

Description of Actual Data Sample:
  • Sample size: N= 5,390
  • Age: 45 to 84 years
  • Gender: 54% women
  • Race/ ethnicity:
    • 43% White
    • 24% Black
    • 20% Hispanic
    • 13% Chinese.
  • Socioeconomic status: Annual salary (as reported):
    • Approximately 22% made less than $20,000
    • Approximately 42% made more than $50,000.
  • Baseline health status: Subjects free of type 2 diabetes (T2D) and cardiovascular disease (CVD)
  • Baseline distribution of dietary patterns (MedDiet score):
    • Quintile 1: N=1,240
    • Quintile 2: N=967
    • Quintile 3: N=1,051
    • Quintile 4: N=932
    • Quintile 5: N=1,200.
Summary of Results:

Model Adjustments

  • Type 2 diabetes, comparing highest to lowest quintiles of MedDiet score:
    • Total population: HR=1.09 (95% CI: 0.80 to 1.49; P for trend = 0.51, NS) Model 3
    • Men: HR=1.11 (95% CI: 0.70 to 1.76; P for trend = 0.69, NS) Model 3
    • Women: HR=1.12 (95% CI: 0.74 to 1.71; P for trend = 0.55, NS) Model 3.
  • No association between MedDiet score and type 2 diabetes in racial/ethnic groups (data not shown):
    • Model 1: Adjusted for age, sex, race/ethnicity and study site
    • Model 2: Adjusted for Model 1 plus educational level, family income, smoking status, physical activity and total energy intake
    • Model 3: Adjusted for Model 2 plus waist circumference
 Confounders
 Total Energy Intake BMI Sex Age Smoking Alcohol Intake Physical Activity
 x    x x  x    x

 

Author Conclusion:

Greater adherence to a Mediterranean-style diet, reflected by a higher a priori MedDiet score, was cross-sectionally associated with lower insulin levels among non-diabetics, and with lower blood glucose before adjustment for obesity, but not associated with a lower incidence of T2D.As stated by authors.

Strengths and Limitations

Strengths

The study had several strengths, including:

  • The diverse population
  • Use of objectively identified diabetes (not only self-report)
  • The highly standardized serum processing, anthropometric measurements and covariate assessment across the study centers.

Limitations

There were limitations that may explain the lack of association in the MESA population between the MedDiet score and incident diabetes.

  • The MedDiet score might be inadequate for a multi-ethnic population in the US, with dietary patterns very different from those of Mediterranean countries
  • The present study attempted to define a Mediterranean dietary pattern from usual diets of participants using a dietary assessment tool not specifically designed to measure conformity to the MedDiet. Not all of the distinct food components of the traditional MedDiet were included in the questionnaire (e.g., olive oil).
  • Measurement error associated with changes in the diet over the duration of follow-up could cause misclassification of the exposure.

Reviewer Comments:

None listed.