Development and validation of a food frequency questionnaire in adult Saudi subjects in Jeddah city

In Saudi Arabia, very limited studies have been conducted to evaluate the validity of culturally appropriate food frequency questionnaire (FFQ). The aim of this study was to validate a newly designed FFQ against two reference methods in Saudi adults.

A new FFQ adapted from the Block FFQ was completed via interview and validated against three-day food records (3DFRs; n = 126) and 24-hour urinary urea nitrogen (UUN)-based protein intake estimates (n = 118) in adult Saudis living in Jeddah. FFQ-estimated nutrient intake was compared to the 3DFR and UUN methods using Pearson's correlations (r), Bland-Altman plots, and weighted kappa (κ_w) statistics.

This study included 126 participants (80 females and 46 males). The FFQ generally overreported nutrient intakes compared to the reference methods. The FFQ was strongly correlated with 3DFRs for energy, protein, carbohydrate, and total fat (r > 0.7); moderately correlated with cholesterol (r = 0.55) and iron (r = 0.44); and weakly correlated with the other micronutrients (r = 0.1-0.3). A moderate positive correlation for protein intake was found (r = 0.62) between the FFQ and 24-hour UUN method. The Bland-Altman analysis indicated the FFQ had an acceptable level of agreement with no significant proportional bias (P > 0.05) with the 3DFRs for energy, protein, total fat, and iron and with protein intake. Similarly, an acceptable level of agreement was found between the FFQ and the 24-hour UUN method for estimating protein intake. Cross-classification analysis showed that ≥ 50% of participants were ranked within the same quartile for energy, protein, and total fat. The FFQ showed good agreement with the 3DFRs for energy and protein (κ_w ≥ 0.61) and acceptable agreement with protein intake. An acceptable agreement was reported between the FFQ and 24-hour UUN method (κ_w = 0.56). Separate analyses of females and males showed stronger correlations and agreements between the FFQ and the two reference methods only in females.

The developed FFQ is an effective and valid tool for assessing dietary intake in Saudi adults. However, it still requires future optimization to improve its validity.