Validation study of a self-administered diet history questionnaire for estimating amino acid intake among Japanese adults.

BACKGROUND AND OBJECTIVES: Despite growing interest in the association between dietary amino acid intake and optimal health, validated dietary questionnaires that can estimate amino acid intake have been scarce. We examined the validity of amino acid intakes estimated using a self-administered diet history questionnaire (DHQ) comparing with 16-day semi-weighed dietary records (DR).

METHODS AND STUDY DESIGN: A total of 184 Japanese men and women completed a four-day DR and a DHQ four times, once in each season. Dietary amino acid intakes were estimated as crude, energy-adjusted, and percentage of total protein intake (% protein) using an amino acid database of Japanese foods. The validity of dietary amino acid intake estimated by the first-time DHQ was examined using the mean of 16 days' DRs as reference.

RESULTS: Mean intakes of almost all amino acids estimated by DHQ were significantly lower than those estimated by the DR for energy-adjusted values in both sexes. Although mean amino acid intakes estimated by DHQ were significantly higher than those estimated by the DR for % protein value, the differences between the DR and DHQ were slight (-0.04 to 0.39% protein for men, -0.05 to 0.37% protein for women). Pearson correlation coefficients between DHQ and the DR showed reasonable ranking ability in % protein values for men (interquartile range (Q1-Q3): 0.31-0.47) and energy-adjusted values for women (interquartile range (Q1-Q3): 0.40-0.45).

CONCLUSION: DHQ showed acceptable ability to estimate mean amino acid intake and to rank individuals in a population according to their amino acid intake for using in large-scale epidemiological studies.