Qualitative methods to evaluate Mediterranean diet in adults.

OBJECTIVE: To fulfil a comprehensive approach to consumption, which is necessary to characterise food habits and their relationship to diseases, using a diet quality index (DQI) developed for a Mediterranean region (Med-DQI).
SETTING: A cross-sectional nutritional survey provided the data for the construction of the DQI.
SUBJECTS: A representative sample made up of 964 subjects from a French Mediterranean area, Hérault département.
METHODS: Foods such as olive oil, fish and cereals were used instead of nutrients to build up scores which constructed the Med-DQI. Biochemical analysis identified biomarkers used to validate the Med-DQI. Correspondence factorial analysis illustrated the characteristics of subjects with different scores given by the Med-DQI.
RESULTS: The subjects could be satisfactorily classified by the Med-DQI. The oldest age, less educated, overweight, manual workers, living in a rural area and male classes showed a better Med-DQI. For women, they were also from the oldest age class, but some of them were from the upper social class, with an ideal BMI and lived by the Mediterranean shore. A composite biomarker index, based on plasma carotene and vitamin E levels and the percentage of EPA and DHA in erythrocytes membranes, can identify subjects with good and poor Med-DQI.
CONCLUSION: Med-DQI G is a good instrument to identify groups at risk with regard to nutritional quality. SUBJECTS with alpha + beta-carotene levels >1 mg/l, vitamin E > 30 mg/l, EPA > 0.65% and DHA > 4% of fatty acids in erythrocytes are likely to have a good diet.