Abstract
A food frequency questionnaire that estimates dietary protein intake was evaluated for accuracy in 30 individuals with phenylketonuria, a genetic disease treated with a protein-restricted diet. The food frequency questionnaire, a novel tool, was compared with a standard 3-day diet record twice during an 8-week period. Findings showed strong Pearson correlations for visits 1 and 2 (r = 0.92 and r = 0.97, P < .001, respectively) and good agreement using Bland-Altman plots. Student t tests demonstrated no significant difference between methods at visit 1 (<0.5 g; P = .99) or visit 2 (<0.5 g; P = .88). The food frequency questionnaire provides an alternative tool to measure average protein consumption in individuals with phenylketonuria.