Validity and reliability of a self-administered food frequency questionnaire for the JPHC study: The assessment of amino acid intake

Background: The Japanese database of food amino acid composition was revised in 2010 after a 24-year interval. To examine the impact of the 2010 revision compared with that of the 1986 revision, we evaluated the validity and reliability of amino acid intakes assessed using a food frequency questionnaire (FFQ).

Methods: A FFQ including 138 food items was compared with 7-day dietary records, completed during each distinct season, to assess validity and administered twice at approximately a 1-year interval, to assess reliability. We calculated amino acid intakes using a database that compensated for missing food items via the substitution method. Subjects were a subsample of two cohorts of the Japan Public Health Center-based prospective study. A total of 102 men and 113 women in Cohort I and 174 men and 176 women in Cohort II provided complete dietary records and the FFQ, of whom 101 men and 108 women of Cohort I and 143 men and 146 women of Cohort II completed the FFQ twice.

Results: In the comparison of the FFQ with dietary records, the medians (ranges) of energy-adjusted correlation coefficients for validity were 0.35 (0.25-0.43) among men and 0.29 (0.19-0.40) among women in Cohort I, and 0.37 (0.21-0.52) and 0.38 (0.24-0.59), respectively, in Cohort II. Values for reliability were 0.47 (0.42-0.52) among men and 0.43 (0.38-0.50) among women in Cohort I, and 0.59 (0.52-0.70) and 0.54 (0.45-0.61), respectively, in Cohort II.

Conclusions: The FFQ used in our prospective cohort study is a suitable tool for estimating amino acid intakes.