Validation of a food frequency questionnaire for assessing total antioxidant status

Abstract

Objective: To evaluate the validity of a food frequency questionnaire (FFQ) developed as a tool for assessing antioxidant intake and to investigate whether dietary total antioxidant status predicted plasma antioxidant status.

Material and methods: This research was conducted at Sağlık Bilimleri University Faculty of Medicine Immunology. Dietary intake of total antioxidants was assessed using an FFQ (82 food items), which was adopted from Satia et al. and translated into Turkish. Total antioxidant status (TAS) in plasma was assessed using enzyme-linked immunosorbent assay (ELISA) in overnight-fasting blood. The validation of the questionnaire against plasma TAS was examined using Spearman's correlation test, Bland-Altman plots, and kappa statistics.

Results: The mean age of the 45 study participants (19 women and 26 men) was 45.9 ± 11.0 years. The mean plasma TAS level was 13.8 ± 6.1 mg/L, and the mean intake of total antioxidants was 114.0 ± 134.6 mg/day. There was a positive correlation between plasma TAS and the intake of total antioxidants calculated using the FFQ (r = 0.73; p < 0.001). Cronbach's alpha coefficient of the questionnaire was 0.949.

Conclusion: The FFQ adapted to the Turkish population and tested here was a good predictor for dietary intake of total antioxidant status.

Keywords: Antioxidants; Nutrition assessment; Validation study.