Biochemical validation of the older Australian's food frequency questionnaire using carotenoids and vitamin E.

Background: Validation of a food frequency questionnaire (FFQ) is important, as inaccurate and imprecise information may affect the association between dietary exposure and health outcomes.

Objective: This study assessed the validity of the Older Australian's FFQ against plasma carotenoids and Vitamin E.

Methods: A random subsample (n = 150) of 2420 participants in the Hunter Community Study, aged 55-85 years, were included. Correlations between crude and energy-adjusted FFQ estimates of carotenoids, Vitamin E, and fruit and vegetables with corresponding biomarkers were determined. Percentages of participants correctly classified in the same quartile, and in the same ± 1 quartile, by the two methods were calculated.

Results: Significant correlations (P < 0.05) were observed for α-carotene (r = 0.26-0.28), β-carotene (r = 0.21-0.25), and β-cryptoxanthin (r = 0.21-0.23). Intakes of fruits and vegetables also showed similar correlations with these plasma carotenoids. Lycopene was only significantly correlated with fruit and vegetable intakes (r = 0.19-0.23). Weak correlations were observed for lutein + zeaxanthin (r = 0.12-0.16). For Vitamin E, significant correlation was observed for energy-adjusted FFQ estimate and biomarker (r = 0.20). More than 68% of individuals were correctly classified within the same or adjacent quartile, except for lutein + zeaxanthin.

Conclusions: With the exception of lutein + zeaxanthin, the Older Australian's FFQ provides reasonable rankings for individuals according to their carotenoids, Vitamin E, fruit and vegetable intakes.