Food and Nutrient Intakes Assessed with Dietary Records for the Validation Study of Self-administered Food Frequency Questionnaire in JPHC Study Cohort I

We present here the survey methods and basic results of dietary records which were used as reference values in the present validation study of a self-administered food frequency questionnaire (FFQ) for the 5-year follow-up survey of the JPHC study. A semi-weighed dietary record was kept for four seven consecutive days in each of the four seasons in 3 areas, i.e., Iwate, Akita, and Nagano, and for seven consecutive days in both winter and summer in Okinawa. The mean intakes were significantly different between areas for some nutrients and food groups. A significant seasonal difference in the mean intakes was also observed in some nutrients such as carotene and vitamin C, and in some food groups such as potatoes, vegetables, and fruits in both sexes, and alcoholic beverages in men and milks in women (p<0.001).


Data Collection
Semi-weighed dietary records of four different seasons over seven consecutive days were collected by a method used in the National Nutrition Survey (NNS)1 with some modifications.Research dietitians instructed the subjects to record all foods and beverages prepared and consumed in a specially designed booklet.The participants were asked to provide detailed descriptions of each food, including the methods of preparation and recipes whenever possible.The dieticians checked the records at each participant's home during the survey and reviewed them in a standardized way after recording.

Coding
All foods ingested were coded with food codes by trained dietitians mainly in one laboratory.Some cooked foods and menus for which it was difficult to estimate the food items used in the preparation were coded with prepared cooked foods/menu codes by the authors and converted into food items after the coding using the standard recipe database developed by the authors.For rice, wellmilled rice was used for the computation.Water including cooking water such as water added for rice-boiling and for miso (fermented soybean paste)-soup was not included in the coding.The weight in grams was also coded for all foods ingested except for cooking water and some beverages.Dietary supplements were coded using temporary codes prepared by the authors, but the weights were not coded.

Computation of Food and Nutrient Intakes
Nutrient intakes were calculated using the Standard Tables of Food Composition in Japan, the 4th revised edition2 for energy and 16 nutrients.As the food composition results from the NNS by dividing the difference between mean intake of our study and the NNS by mean intake of the NNS (percent difference).

RESULTS
Tables 1 and 2 show the intake levels of energy and main nutrients by sex and area.The mean energy intake was highest in the Ninohe PHC area, and lowest in the Ishikawa PHC area for both men and women.Mean intakes were significantly different among areas for most of the nutrients except alcohol, retinol, niacin and vitamin C for both sexes, and for total fat, carotene, vitamin B1 and B2 for women (p<0.05).Mean intakes were close to the values reported in the NNS among similar age-groups in the same year,1 i.e., difference within 10% for all nutrients examined except for sodium and vitamin C in both sexes.After adjustment for energy, the area differences were significant only for total fat, carbohydrate, calcium, sodium, carotene, niacin for both sexes, and for vitamin B2 and C for men (p<0.05).
Tables 3 and 4 show the intake levels of main nutrients by season and sex.A significant seasonal difference was observed in the mean intake of iron, carotene and vitamin C in both men and women, and in the mean intake of carbohydrate, calcium , sodium, and retinol in women (p<0.05) when the crude intakes in the 3 areas were examined.When the values in the 4 areas were examined between summer and winter, a significant seasonal difference was observed in the mean intake of iron and carotene in both sexes, and for calcium, retinol and vitamin B1 in women .When the energy-adjustment values in the 3 areas were examined , a significant seasonal difference was observed in the mean intake of protein, iron, potassium, carotene, niacin and vitamin C in men, and in total fat, carbohydrate, calcium, iron, sodium , potassium, retinol, carotene, vitamin B2, vitamin C in women (p<0 .05).When the energy-adjusted values in 4 areas were examined between summer and winter, a significant seasonal difference was observed in the mean intake of protein , iron, potassium and retinol in men, and in protein, calcium , iron, potassium, retinol, carotene, vitamin B1 and vitamin B2 in women .
Tables 5 and 6 show the intake levels of food groups by sex and area.Mean intakes were significantly different among the 4 areas in most of the food groups except for potatoes and starches , and alcoholic and nonalcoholic beverages in both sexes , algae in men, and green and yellow vegetables , and milks in women (p<0.05).The difference between the observed intakes and the reported ones from the NNS was 040% to 60% larger tha n that observed for nutrients.After the adjustment for energy , the area differences were significant for most of the food groups with th e exception of cereals, sugar and sweeteners , eggs, vegetables , algae and non-alcoholic beverages in men, and except for cereals, potatoes and starches, eggs, milks, vegetables, green and yellow vegetables, and alcoholic beverages in women (p<0 .05).
Tables 7 and 8 show the intake levels of food groups by seas on and sex.A significant seasonal difference was observed in th e mean intake of potatoes and starches, fats and oils, vegetables, green and yellow vegetables, pickled vegetables, fruits, fungi, algae, alcoholic beverages in men, and in the mean intake of potatoes and starches, fats and oils, pulses, milks, vegetables, green and yellow vegetables, pickled vegetables, fruits and fungi among women (p<0.05), when the crude values in the 3 areas were examined.In the 4 areas, a significant seasonal difference was observed between summer and winter in the mean intake of potatoes and starches, sugar and sweeteners, nuts and seeds, milks, vegetables, pickled vegetables, fruits, fungi, algae, and alcoholic beverages in men, and in the mean intake of potatoes and starches, fats and oils, nuts and seeds, pulses, milks, vegetables, green and yellow vegetables, pickled vegetables, fruits and -fungi in women (p<0.05).This seasonal difference in 3 areas was consistent after energy adjustment for most food groups except confectioneries in men (p<0.05).The seasonal difference in 4 areas was also consistent for most food groups aside from milks and algae in men, and alcoholic beverages in women (p<0.05).Tables 9-25 showed the cumulative percent contributions of the top 20 foods for each nutrient.DISCUSSION A wide variation was observed among the 4 areas both for food and nutrient intake levels at the population level.However, mean intakes of energy and the selected 7 nutrients were not markedly different from the mean values observed in the NNS during a similar period: the difference was within 10% for most of the nutrients compared.The area difference was less marked when energy-density values were used than when the crude values were used in the analysis.
Reports on seasonal differences in nutrient and food group intakes have been few in Japanese populations.6Our data revealed a significant seasonal difference for more than a few nutrients and food groups in both crude and energy-density values.These findings were in general agreement with the previous reports in different areas of Japan.6 The data indicated the importance of considering seasonal differences in food group intakes and some specific nutrients such as carotene and vitamin C, where long-term dietary habits are concerned.DRs from the Okinawa (Ishikawa PHC) area were collected only in winter and summer because the seasonal variation was expected to be minimal in a sub-tropical climate.Thus, seasonal differences in dietary habits in the Ishikawa PHC area were not investigated in the present study.
When the intakes were compared between winter and summer including the data of the Ishikawa PHC area, the results were virtually consistent.
The top 20 foods contributing to intake of each nutrient in DRs were included in the FFQ food items, except for some which contributed to alcohol, carbohydrate, and sodium intakes.The lowest cumulative percentage among the top 20 foods was observed in potassium in men (46%) and in women (44%).The cumulative percentage among the top 20 foods was slightly lower in women than in men in most of the nutrients examined.The results were generally similar to those previously reported for a different population in Japan.7.8 Table 2. Nutrient intakes (energy density) assessed with DR by area       2 Data on subjects in Ishikawa PHC (14-day data) were counted twice for (28-day data).
1 ANOVAwas used to test for the difference among areas.Table 9. Cumulative % contribution of the top 20 foods for energy assessed by DR 1 Food codes and descriptions correspond to those of the Standard Tables of Food Composition, 4th revised edition in Japan by Science and Technology Agency. 2 Data on subjects in Ishikawa PHC (14 -day data) were counted twice for 28-day data .
Table 20.Cumulative % contribution of the top 20 foods for carotene assessed by DR1 Food codes and descriptions correspond to those of the Standard Tables of Food Composition, 4th revised edition in Japan by Science and Technology Agency. 2 Data on subjects in Ishikawa PHC (14-day data) were counted twice for (28-day data).
Table 21.Cumulative % contribution of the top 20 foods for thiamin assessed by DR1 Food codes and descriptions correspond to those of the Standard Tables of Food Composition , 4th revised edition in Japan by Science and Technology Agency. 2 Data on subjects in Ishikawa PHC (14-day data) were counted twice for (28 -day data) .
Table 22.Cumulative % contribution of the top 20 foods for riboflavin assessed by DR1 Food codes and descriptions correspond to those of the Standard Tables of Food Composition, 4th revised edition in Japan by Science and Technology Agency. 2 Data on subjects in Ishikawa PHC (14-day data) were counted twice for (28-day data).
Table 23.Cumulative % contribution of the top 20 foods for niacin assessed by DR 1 Food codes and descriptions correspond to those of the Standard Tables of Food Composition , 4th revised edition in Japan by Science and Technology Agency. 2 Data on subjects in Ishikawa PHC (14-day data) were counted twice for (28 -day data) .
table for cholesterol

Table 10 .
Cumulative % contribution of the top 20 foods for protein assessed by DR 1 Food codes and descriptions correspond to those of the Standard Tables of Food Composition, 4th revised edition in Japan by Science and Technology Agency. 2 Data on subjects in Ishikawa PHC (14-day data) were counted twice for (28-day data).

Table 11 .
Cumulative % contributionof the too 20 foods for fat assessed by DR 1 Food codes and descriptions correspond to those of the Standard Tables of Food Composition , 4th revised edition in Japan by Science and Technology Agency.2Data on subjects in Ishikawa PHC (14-day data) were counted twice for (28-day data) .

Table 12 .
Cumulative % contribution of the top 20 foods for carbohydrate assessed by DR

Table 13 .
Cumulative % contribution of the top 20 foods for alcohol assessed by DR Food codes and descriptions correspond to those of the Standard Tables of Food Composition , 4th revised edition in Japan by Science and Technology Agency.2Data on subjects in Ishikawa PHC (14-day data) were counted twice for (28-day data).

Table 14 .
Cumulative % contribution of the top 20 foods for calcium assessed by DR 1 Food codes and descriptions correspond to those of the Standard Tables of Food Composition, 4th revised edition in Japan by Science and Technology Agency. 2 Data on subjects in Ishikawa PHC (14-day data) were counted twice for (28-day data).

Table 15 .
Cumulative % contribution of the top 20 foods for phosphorus assessed by DR 1 Food codes and descriptions correspond to those of the Standard Tables of Food Composition , 4th revised edition in Japan by Science and Technology Agency. 2 Data on subjects in Ishikawa PHC (14-day data) were counted twice for (28-day data) .

Table 16 .
Cumulative % contribution of the top 20 foods for iron assessed by DR 1 Food codes and descriptions correspond to those of the Standard Tables of Food Composition, 4th revised edition in Japan by Science and Technology Agency.

Table 17 .
Cumulative % contributionof the top 20 foods for sodium assessed by DR 1 Food codes and descriptions correspond to those of the Standard Tables of Food Composition , 4th revised edition in Japan by Science and Technology Agency. 2 Data on subjects in Ishikawa PHC (14-day data) were counted twice for (28 -day data) .

Table 19 .
Cumulative % contribution of the top 20 foods for retinol assessed by DR 1 Food codes and descriptions correspond to those of the Standard Tables of Food Composition , 4th revised edition in Japan by Science and Technology Agency. 2 Data on subjects in Ishikawa PHC (14-day data) were counted twice for (28-day data) .

Table 25 .
Cumulative % contribution of the top 20 foods for cholesterol assessed by DR