Reproducibility and relative validity of a food frequency questionnaire to assess dietary intake of adults living in a Mediterranean country

OBJECTIVE: Food frequency questionnaires (FFQs) must be validated among the population of interest due to the specificities in dietary habits, culture and food in each country of the Mediterranean region. The objective of this study was to determine the relative validity and reproducibility of a 157 item semi-quantitative FFQ among Lebanese adult population. MATERIAL AND METHODS: Dietary intake was assessed through dietary recalls, a FFQ with food items, and traditional recipes from the Mediterranean cuisine. Validity of the FFQ was measured by comparing the intake of calories, macro and micronutrients to the mean values derived from three dietary recalls (DR). Reproducibility of the FFQ was evaluated after repeating the same FFQ among the participant after a four-month period. RESULTS: 114 healthy adults aged between 18 and 60 years of which 52.6% are men participated in this study. 53 of these adults participated in the reproducibility study. Intra class correlation coefficient (ICC) between the two FFQ measurements ranged from 0.822 for sodium to 0.998 for energy indicating excellent reproducibility. The FFQ showed slightly higher intakes than the dietary recalls for most of the nutrients and foods reaching 2.1% for nutrients (polyunsaturated fatty acids) and 18% for food groups (olive oil). Correlation coefficients ranged between 0.783 (sodium) and 0.996 (carbs) for nutrients and between 0.906 (fish) and 1 (fruits and nuts) for food groups, with a significant p value (p = 0.038 for folate). Cross-classification of nutrients into quartiles showed that more than 81% of the participants were classified in the same quartile. Misclassifications were low for most nutrients with one to three persons misclassified at the extreme quartiles. CONCLUSION: The FFQ used in this research contained western and Mediterranean type of dishes and foods. Statistical analysis showed good reproducibility and validity of the tested tool in a heterogeneous sample of adults living in a Mediterranean country. It is a useful tool for future investigations and strategies promoting the comeback of this traditional diet.