Validity and Reproducibility of a Food Frequency Questionnaire for Dietary Assessment in Japanese People.

A 76-item food frequency questionnaire (FFQ) was developed to investigate nutritional epidemiology in urban residents in Japan. The authors prepared two food models-a life-size three-dimensional model and a life-size two-dimensional photograph-to assess the FFQ portion size. The validity of the FFQ was verified using the two food models by comparing them with 16-d weighted dietary records (WDRs). Validation was conducted by comparing the FFQ1 findings with those obtained with the WDR, which is regarded as the gold standard, and reproducibility was verified by comparing the findings from FFQ2 and FFQ1. After completion of the WDR, the participants were randomized into two groups. In one group, the FFQ was conducted using life-size three-dimensional models (3D-FFQ) to estimate the portion size. In the other group, the FFQ was administered using life-size photo collection (2D-FFQ). Regarding validity, the median values (range) of Pearson's correlation coefficients for the energy and nutrient intake of the 32 items by the WDR and FFQ1 were r=0.53 (0.30-0.68) in the 3D-FFQ and r=0.57 (0.33-0.87) in the 2D-FFQ. When FFQs with 2D or 3D food models and two different portion sizes were compared with regard to the intake of certain food groups, energy, and nutrients, both the 2D-FFQ and 3D-FFQ provided good correlation coefficients with the WDR.

Applying a meal coding system to 16-d weighed dietary record data in the Japanese context: towards the development of simple meal-based dietary assessment tools.

Data on the combination of foods consumed simultaneously at specific eating occasions are scarce, primarily due to a lack of assessment tools. We applied a recently developed meal coding system to multiple-day dietary intake data for assessing its ability to estimate food and nutrient intakes and characterise meal-based dietary patterns in the Japanese context. A total of 242 Japanese adults completed sixteen non-consecutive-day weighed dietary records, including 14 734 eating occasions (3788 breakfasts, 3823 lunches, 3856 dinners and 3267 snacks). Common food group combinations were identified by meal type to identify a range of generic meals. Dietary intake was calculated on the basis of not only the standard food composition database but also the substituted generic meal database. In total, eighty generic meals (twenty-three breakfasts, twenty-one lunches, twenty-four dinners and twelve snacks) were identified. The Spearman correlation coefficients between food group intakes calculated based on the standard food composition database and the substituted generic meal database ranged from 0·26 to 0·85 (median 0·69). The corresponding correlations for nutrient intakes ranged from 0·17 to 0·82 (median 0·61). A total of eleven meal patterns were established using principal components analysis, and these accounted for 39·1 % of total meal variance. Considerable variation in patterns was seen in meal type inclusion and choice of staple foods (bread, rice and noodles) and drinks, and also in meal constituents. In conclusion, this study demonstrated the usefulness of a meal coding system for assessing habitual diet, providing a scientific basis towards the development of simple meal-based dietary assessment tools.

Within- and between-individual variation in energy and nutrient intake in Japanese adults: effect of age and sex differences on group size and number of records required for adequate dietary assessment.

BACKGROUND: Information on within- and between-individual variation in energy and nutrient intake is critical for precisely estimating usual dietary intake; however, data from Japanese populations are limited. METHODS: We used dietary records to examine within- and between-individual variation by age and sex in the intake of energy and 31 selected nutrients among Japanese adults. We also calculated the group size required to estimate mean intake for a group and number of days required both to rank individuals within a group and to assess an individual's usual intake, all with appropriate arbitrary precision. A group of Japanese women (younger: 30-49 years, n = 58; older: 50-69 years, n = 63) and men (younger: 30-49 years, n = 54; older: 50-76 years, n = 67) completed dietary records for 4 nonconsecutive days in each season (16 days in total). RESULTS: Coefficients of within-individual variation and between-individual variation were generally larger in the younger group than in the older group and in men as compared with women. The group size required to estimate a group's mean intake, and number of days required to assess an individual's usual intake, were generally larger for the younger group and for men. In general, a longer period was required to rank women and older adults. CONCLUSIONS: In a group of Japanese adults, coefficients of within-individual variation and between-individual variation, which were used to estimate the group size and number of records required for adequate dietary assessment, differed by age, sex, and nutrient.

Comparability of weighed dietary records and a self-administered diet history questionnaire for estimating monetary cost of dietary energy.

An increasing number of studies have estimated monetary diet cost using various dietary assessment methods, based on databases on retail food prices, for investigating its association with dietary intake and health outcomes. However, information regarding the comparability of monetary diet cost across dietary assessment methods is absolutely lacking. This study compared monetary cost of dietary energy estimated from weighed dietary records (DRs) with that estimated from a self-administered diet history questionnaire (DHQ). The subjects were 92 Japanese women aged 31-69 years and 92 Japanese men aged 32-76 years. The DHQ (assessing diet during the preceding month) and 4-day DRs (one weekend day and three weekdays) were completed in each season over a 1-year period (DHQs1-4 and DRs1-4, respectively). An additional DHQ was completed at one year after completing DHQ1 (DHQ5). Monetary cost of dietary energy (Japanese yen/4184 kJ) was calculated using food intake information derived from each dietary assessment method, based on retail food prices. Pearson correlation between the mean of DRs1-4 and mean of DHQs1-4 was 0.64 for women and 0.69 for men. Pearson correlation between the mean of DRs1-4 and DHQ1 was 0.60 for women and 0.52 for men, while intraclass correlation between DHQ1 and DHQ5 was 0.64 for women and 0.51 for men. These data indicate reasonable comparability of monetary cost of dietary energy across DR and a DHQ as well as usefulness of a single administration of the DHQ for estimating monetary cost of dietary energy.