Literature DB >> 21963789

Validity of a self-administered food frequency questionnaire for middle-aged urban cancer screenees: comparison with 4-day weighed dietary records.

Ribeka Takachi1, Junko Ishihara, Motoki Iwasaki, Satoko Hosoi, Yuri Ishii, Shizuka Sasazuki, Norie Sawada, Taiki Yamaji, Taichi Shimazu, Manami Inoue, Shoichiro Tsugane.   

Abstract

BACKGROUND: The validity of estimates of dietary intake calculated using a food frequency questionnaire (FFQ) depends on the specific population. The 138-item FFQ used in the 5-year follow-up survey for the Japan Public Health Center-based Prospective Study was initially developed for and validated in rural residents. However, the validity of estimates based on this FFQ for urban residents, whose diet and lifestyle differ from those of rural residents, has not been clarified. We examined the validity of ranking individuals according to level of dietary consumption, as estimated by this FFQ, among an urban population in Japan.
METHODS: Among 896 candidates randomly selected from examinees of cancer screening provided by the National Cancer Center, Japan, 144 participated in the study. In 2007-2008, at an average 2.7 years after cancer screening, participants were asked to respond to the questionnaire and to provide 4-day weighed diet records (4d-DRs) for use as the reference intake. Spearman correlation coefficients (CCs) between the FFQ and 4d-DR estimates were calculated, after correction for intraindividual variation of 4d-DRs.
RESULTS: The median (range) deattenuated CC for men and women was 0.57 (0.23 to 0.89) and 0.47 (0.08 to 0.94), respectively, across 45 nutrients and 0.51 (0.10 to 0.98) and 0.51 (-0.36 to 0.88) for 43 food groups.
CONCLUSIONS: Although the FFQ was developed for a rural population, it provided reasonably valid measures of consumption for many nutrients and food groups in middle-aged screenees living in urban areas in Japan.

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Mesh:

Year:  2011        PMID: 21963789      PMCID: PMC3899461          DOI: 10.2188/jea.je20100173

Source DB:  PubMed          Journal:  J Epidemiol        ISSN: 0917-5040            Impact factor:   3.211


INTRODUCTION

Accuracy in measuring individual dietary intake is an important issue in the analysis and evaluation of results from epidemiologic studies of the association between diet and disease. Food frequency questionnaires (FFQs) provide a view of usual food or nutrient intake over time and have been developed and validated in target populations of epidemiologic studies.[1] Because the foods listed in an FFQ are selected according to their percentage contribution to the total consumption of nutrients among representatives of the target population for whom the FFQ is to be used, they might not necessarily reflect the foods eaten by a different population. Further, accuracy in remembering foods consumed appears to differ by education level and the degree of interest in diet.[1] The validity of FFQ estimates of dietary intake therefore appears to depend on the specific population. The FFQ used for the Japan Public Health Center-based Prospective Study 5-year follow-up survey was developed for use with residents of rural cohort areas.[2] Of these resident, 27% worked in management, clerical, sales, or services, and 21% were employed in the agriculture, forestry, and fisheries sector.[3] Further, the FFQ was validated among subsamples of these rural residents.[4]–[6] It is therefore unclear whether this FFQ is accurate in estimating dietary intake among Japanese with an urbanized lifestyle. In addition, to our knowledge no such validation study has been restricted to an examination of subjects living in urban and adjacent areas.[7] To confirm the suitability of this FFQ for use in epidemiologic studies of cancer screenees at the National Cancer Center, such as the participants in the Colorectal Adenoma Study in Tokyo, we evaluated the validity and reproducibility of ranking individuals by levels of dietary consumption—as estimated by this FFQ after minor modification—as a means of assessing dietary intake among middle-aged urban cancer screenees.[8]

METHODS

Study setting and participants

The study participants were selected from adults who underwent cancer screening at the Research Center for Cancer Prevention and Screening, National Cancer Center, “Japan from January 2004 through July 2006. Eligibility criteria were age between 40 and 69 years, residence in metropolitan Tokyo, and no previous or present diagnosis of cancer, cardiovascular disease, or diabetes mellitus. Eligible subjects were stratified by sex and age (40–49, 50–59, and 60–69 years) and randomly numbered for recruiting priority. Among the 896 invited candidates, 187 (response rate: 20.9%) agreed to participate in the study. After excluding those who could not attend the study orientation, 144 participated in the study. As an incentive to participate, participants received a report of their results regarding the consumption of energy and nutrients based on 4-day dietary records, a small gift (an instrument for measuring the salt concentration of soup), and a free invitation to attend a class on healthful cooking. The study was approved by the Institutional Review Board of the National Cancer Center, Tokyo, Japan. All participants provided their written informed consent for participation, at the study orientation.

Data collection

The reference intake was 4-day weighed diet records (4d-DRs), which were obtained over 4 consecutive days during the period from May 2007 through April 2008. Before the start of data collection, all participants were invited to attend the study orientation, where the 4d-DR procedure was explained by trained dietitians. The self-administered FFQ was first administered during 2004–2006 at the time of cancer screening (FFQ0) and then during 2007–2008 at the orientation session (FFQ1).

Dietary assessment

The 4d-DR included 3 weekdays and 1 weekend day and was used as the reference method. Food portions were measured by each participant during meal preparation using supplied digital scales and measuring spoons and cups. For foods purchased or consumed outside the home, the participants were instructed to record the approximate quantity of all foods in the meal and/or the names of the product and company. Daily weighed records were faxed to the study office at the Research Center for Cancer Prevention and Screening, National Cancer Center on the morning after completion of that day’s record. Trained dietitians checked the record with the examinee by telephone and coded the foods and weights. Stores and restaurants were asked about the recipes of certain meals eaten outside the home. The FFQ consisted of 138 food and beverage items and 9 frequency categories, which ranged from almost never to 7 or more times per day (or to 9 glasses per day, for beverages), and asked about the usual consumption of listed foods during the previous year. The food list, which was initially developed for the Japan Public Health Center-based Prospective Study,[2] was modified for a middle-aged urban population as follows: 11 foods mainly consumed in specific areas (Okinawa and Nagano) or at specific times were excluded (luncheon meats, vivipara, qing-geng-cai [bok choy], leaf mustard, bitter gourd, chard, loofah, mugwort, yushi-tofu [soft, boiled tofu], calcium beverages, and beta carotene beverages), and 11 foods consumed throughout the year in urban areas were added (beef, stir-fried; chicken, stir-fried; chicken, stew; low-fat milk; Japanese amberjack; Welsh onion; eggplant; edible burdock; konnyaku foods [devil’s tongue]; and jam, strawberry or marmalade). Portion size was specified for each food item, using 3 standard sizes: medium (the standard amount), small (50% smaller), and large (50% larger). Intakes of energy, 45 nutrients, and 43 food groups were calculated using the Standardized Tables of Food Composition, Fifth revised edition[9],[10] and a specially developed food composition table for isoflavones and lycopene in Japanese foods.[11],[12] We collapsed the individual food items into 18 predefined food groups according, to the Food Composition Tables, and 25 stream-specific subgroups. The grouping scheme for subgroups, eg, cruciferous vegetables and red meat, was based on the similarity of nutrient profiles or culinary usage among the foods and was somewhat similar to that used in other studies.

Statistical analysis

The mean intake of each nutrient and food group estimated using the FFQ1 was compared to that estimated using the 4d-DR among the 143 participants who completed both. Percentage differences were calculated for each nutrient and food group by dividing the difference in intake on the FFQ1 from that on the 4d-DR by those using the 4d-DR. To determine the validity of the FFQ, Spearman rank correlation coefficients (CCs) between intake estimates of the FFQ1 and 4d-DR were calculated for crude and energy-adjusted values. Regression coefficients between nutrient intakes according to the FFQ1 and 4d-DR were calculated for energy-adjusted values to examine the degree of attenuation in a diet–disease association in a hypothetical study using the FFQ.[1] A residual model was used for energy adjustment.[1] We corrected the observed CCs for the attenuating effect of random intraindividual error from the usual intake of each energy and nutrient and each food group. The deattenuated value was corrected using the ratios of the within- to between-individual variances based on the 4-day DRs according to the following formula:where the observed en-CCx is the correlation in energy-adjusted value for nutrient x, λx is the ratio of within- to between-individual variance, and n is the number of dietary records (4 days).[1] To measure the validity of categorization, we computed the number of participants classified into the same, adjacent, and extreme categories by joint classification according to both quintiles using the FFQ1 and the 4d-DR. For reproducibility, CCs between the FFQ1 and FFQ0 were calculated for crude and energy-adjusted values for the 144 participants who completed both FFQs. We confirmed the cumulative percentage among the top 20 foods for energy, because food variety was important in confirming the extent to which the list of FFQ items could be covered. Percentages of the sum of energy by individual foods eaten to total energy during the 4 days were also calculated. All analyses were performed using SAS Version 9.1 (SAS Institute Inc., Cary, NC).

RESULTS

Participants in the validation study

Age distribution (40s, 50s, 60s) at recruitment (2004–2006) was n = 11, 29, and 29, respectively, for men and n = 16, 30, and 29 for women. Mean body mass index (standard deviation) for men and women was 23.5 (2.5) and 21.5 (2.5), respectively. Overall, 51% of the participants were employed in management, clerical, sales, or services, and 2% worked in agriculture, forestry, or fisheries.

Mean intakes and FFQ validity

Table 1 shows daily intakes of energy and 45 nutrients, as assessed by 4d-DR and FFQ1, percentage differences between FFQ1 and the 4d-DR, and their correlations among men and women. Although estimated intake levels for energy were very similar between the 2 methods (difference: −6% for men, 2% for women), the percentage difference in nutrient intake between the 4d-DR and FFQ1 varied from −35% and −20% for beta-carotene to +99% and +198% for cryptoxanthin in men and women, respectively. The CCs of the crude values varied from 0.12 for retinol equivalents to 0.71 for daidzein in men and from 0.10 for polyunsaturated fatty acid to 0.57 for vitamin K in women. The median across the 45 nutrients was 0.43 for both men and women. After energy adjustment and deattenuation, the median CC improved to 0.57 in men and 0.47 in women. The regression coefficient for nutrient intake varied from 0.16 for retinol equivalents to 0.61 for copper in men and from 0.05 for cryptoxanthin to 0.63 for pantothenic acid in women (data not shown).
Table 1.

Energy and nutrient intakes according to food frequency questionnaire 1 (FFQ1), percentage difference between FFQ1 and 4-day diet record (DR), and their correlations in men and women

 Men (n = 69)Women (n = 74)


 4-day DRFFQ1a%bCorrelation coefficientc4-day DRFFQ1a%bCorrelation coefficientc






 Mean ± SDMean ± SDCrudeEnergy-adjustedDeatte-nuateddMean ± SDMean ± SDCrudeEnergy-adjustedDeatte-nuatedd
Energy (kcal)2271 ± 4262141 ± 737−60.480.531842 ± 2981875 ± 73320.290.34
Protein (g)89.2 ± 15.676.2 ± 32.3−150.310.550.6775.0 ± 13.670.5 ± 32−60.560.390.47
Total fat (g)64.6 ± 14.364.6 ± 33.200.270.300.4257.8 ± 16.363.0 ± 32.990.220.280.35
 SFA (g)18.12 ± 4.8520.21 ± 11.23120.270.290.4416.82 ± 5.8420.04 ± 12.21190.370.340.41
 MUFA (g)22.63 ± 6.5622.79 ± 13.1510.310.280.3820.34 ± 7.0622.59 ± 12.41110.260.390.49
 PUFA (g)14.62 ± 3.2113.38 ± 6.73−80.530.530.7212.33 ± 2.9912.4 ± 6.0110.100.240.38
  n-3 PUFA (g)3.10 ± 1.052.58 ± 1.59−170.260.340.562.48 ± 0.912.35 ± 1.28−50.340.280.68
  n-6 PUFA (g)11.45 ± 2.7410.73 ± 5.43−60.580.530.769.79 ± 2.519.97 ± 4.8120.110.310.47
 Cholesterol (mg)367 ± 132303 ± 278−180.310.390.51333 ± 117271 ± 168−190.350.280.38
Carbohydrate (g)301 ± 72.9270.8 ± 99.2−100.580.520.56245.2 ± 46.9245.7 ± 84.400.250.390.43

 Total dietary fiber (g)20.3 ± 6.314.1 ± 6.6−310.550.610.6718.0 ± 4.615.3 ± 7.4−150.440.460.53
  Water soluble (g)4.7 ± 1.73.6 ± 1.9−230.530.590.654.1 ± 1.23.8 ± 1.9−90.440.480.56
  Water insoluble (g)14.3 ± 4.69.9 ± 4.6−310.550.640.7113.0 ± 3.410.9 ± 5.3−160.430.380.44
Sodium (mg)4728 ± 17454269 ± 2312−100.440.420.453943 ± 9443920 ± 1953−10.330.390.47
 Salt equivalent (g)11.9 ± 4.410.8 ± 5.9−90.440.390.429.9 ± 2.49.9 ± 4.900.330.380.46
Potassium (mg)3695 ± 9833072 ± 1208−170.370.600.653204 ± 7082992 ± 1318−70.480.620.70
Calcium (mg)707 ± 234665 ± 423−60.480.580.64637 ± 204657 ± 46930.550.550.61
Magnesium (mg)393 ± 112317 ± 117−190.430.530.58323 ± 64293 ± 125−90.430.450.54
Phosphorus (mg)1395 ± 2961221 ± 512−120.380.570.651183 ± 2271144 ± 569−30.550.400.47
Iron (mg)11.2 ± 3.29.6 ± 3.8−150.450.620.689.3 ± 28.8 ± 3.5−60.460.440.55
Zinc (mg)10.0 ± 2.28.8 ± 3.5−120.400.530.658.7 ± 1.87.8 ± 3.2−100.490.260.34
Copper (mg)1.59 ± 0.411.35 ± 0.54−150.590.670.741.31 ± 0.261.23 ± 0.47−60.350.400.49
Manganese (mg)5.03 ± 2.74.22 ± 1.75−160.540.410.443.93 ± 1.314.35 ± 2.13110.410.370.41

Retinol (µg)318 ± 379364 ± 308140.210.320.56348 ± 528361 ± 27440.130.110.16
Retinol Eq (µg)749 ± 433678 ± 383−100.120.150.23782 ± 560754 ± 412−40.350.240.33
α-carotene (µg)542 ± 381474 ± 387−130.380.370.50667 ± 534632 ± 736−50.510.530.78
β-carotene (µg)4580 ± 26972960 ± 1854−350.340.360.494588 ± 22813658 ± 2751−200.540.530.70
Cryptoxanthin (µg)539 ± 11481071 ± 1262990.500.520.55482 ± 6681439 ± 16561980.150.070.08
Lycopene (mg)6583 ± 78924888 ± 7441−260.480.450.524456 ± 51514319 ± 5617−30.230.330.40
β-carotene Eq (µg)5152 ± 28603731 ± 2289−280.400.390.525194 ± 26254693 ± 3391−100.540.490.62
Vitamin D (µg)11.3 ± 6.57.9 ± 5.8−300.470.520.889.9 ± 6.18.1 ± 6.2−180.340.220.37
α-tocopherol (mg)9.8 ± 3.08.1 ± 4.2−170.260.410.488.6 ± 2.58.1 ± 4.3−60.270.420.51
β-tocopherol (mg)0.4 ± 0.10.4 ± 0.200.340.300.480.3 ± 0.10.4 ± 0.2170.140.210.33
γ-tocopherol (mg)13 ± 412 ± 6.8−80.530.470.6911.1 ± 3.510.9 ± 5.3−10.100.220.33
δ-tocopherol (mg)3.4 ± 1.43 ± 2.1−100.690.680.892.7 ± 0.92.6 ± 1.2−40.180.250.51
Vitamin K (µg)345 ± 194303 ± 306−120.640.670.79290 ± 108270 ± 133−70.570.610.94
Vitamin B1 (mg)1.21 ± 0.381.01 ± 0.43−170.230.470.541.05 ± 0.280.99 ± 0.45−50.440.350.42
Vitamin B2 (mg)1.71 ± 0.551.66 ± 0.79−30.270.380.421.47 ± 0.371.58 ± 0.880.470.460.53
Niacin (mg)24.2 ± 7.320.3 ± 8.6−160.380.360.4419.8 ± 5.219.0 ± 8.4−40.440.260.32
Vitamin B6 (mg)1.91 ± 0.551.57 ± 0.6−180.380.390.441.53 ± 0.41.45 ± 0.63−50.460.490.57
Vitamin B12 (µg)10.8 ± 5.67.9 ± 5.1−270.130.300.578.6 ± 4.67.2 ± 5.1−160.460.360.67
Folate (µg)512 ± 188418 ± 176−180.480.600.66449 ± 124433 ± 194−30.480.350.41
Pantothenic acid (mg)8.02 ± 1.97.66 ± 3.5−40.410.580.676.83 ± 1.57.09 ± 3.1540.530.570.66
Vitamin C (mg)178 ± 82136 ± 83−240.620.670.73156 ± 62163 ± 9640.450.450.51

Daidzein (mg)17.14 ± 9.7820.39 ± 20.45190.710.660.8412.81 ± 7.2814.98 ± 8.08170.490.490.79
Genistein (mg)28.6 ± 16.2734.13 ± 35.71190.690.640.8121.87 ± 12.324.84 ± 13.7140.460.470.75

MEDIAN   0.430.520.57   0.430.390.47

Abbreviations: SD, standard deviation; SFA, saturated fatty acid; MUFA, monounsaturated fatty acid; PUFA, polyunsaturated fatty acid; Eq, equivalent.

aIntakes based on second FFQ, conducted in 2007–2008. bPercentage differences: (FFQ1 − DR)/DR * 100 (%). cSpearman’s rank correlation coefficients based on crude and energy-adjusted values. For men, r ≥ 0.24 = P < 0.05, r ≥ 0.31 = P < 0.01, r ≥ 0.39 = P < 0.001. For women, r ≥ 0.23 = P < 0.05, r ≥ 0.30 = P < 0.01, r ≥ 0.38 = P ≤ 0.001. dDeattenuated CCx = observed CCx * SQRT(1 + λx/n), where λx is the ratio of within- to between-individual variance for nutrient x, and n is number of dietary records; observed CCs were based on energy-adjusted values other than energy intake.

Abbreviations: SD, standard deviation; SFA, saturated fatty acid; MUFA, monounsaturated fatty acid; PUFA, polyunsaturated fatty acid; Eq, equivalent. aIntakes based on second FFQ, conducted in 2007–2008. bPercentage differences: (FFQ1 − DR)/DR * 100 (%). cSpearman’s rank correlation coefficients based on crude and energy-adjusted values. For men, r ≥ 0.24 = P < 0.05, r ≥ 0.31 = P < 0.01, r ≥ 0.39 = P < 0.001. For women, r ≥ 0.23 = P < 0.05, r ≥ 0.30 = P < 0.01, r ≥ 0.38 = P ≤ 0.001. dDeattenuated CCx = observed CCx * SQRT(1 + λx/n), where λx is the ratio of within- to between-individual variance for nutrient x, and n is number of dietary records; observed CCs were based on energy-adjusted values other than energy intake. Table 2 shows daily intakes of 43 food groups assessed by the 4d-DR and FFQ1, the percentage difference between FFQ1 and 4d-DR, and their correlations among men and women. The percent difference in intakes between the 4d-DR and FFQ1 varied from −83% and −86% for seasonings and spices in men and women, respectively, to +111% for other cereals in men and +153% for citrus fruit in women. The CCs of the crude values varied from 0.04 and −0.28 for seasonings to 0.81 and 0.82 for coffee in men and women, respectively. The medians across 43 food groups for men and women were 0.45 and 0.35, respectively. After energy adjustment and deattenuation, the median CC slightly improved to 0.51 (varying from 0.10 for seasonings to 0.98 for noodles) in men and 0.51 (varying from −0.36 for seasonings to 0.88 for coffee) in women.
Table 2.

Food-group intakes according to food frequency questionnaire 1 (FFQ1), percentage difference between FFQ1 and 4-day diet record (DR), and their correlations in men and women

 Men (n = 69)Women (n = 74)


 4-day DRFFQ1a%bCorrelation coefficientc4-day DRFFQ1a%bCorrelation coefficientc






 Mean ± SD(g)Mean ± SD(g)CrudeEnergy-adjustedDeatte-nuateddMean ± SD(g)Mean ± SD(g)CrudeEnergy-adjustedDeatte-nuatedd
Cereals447 ± 173510 ± 215140.670.450.51332 ± 78425 ± 153280.290.330.41
 Rice306 ± 169351 ± 173150.720.420.51210 ± 85259 ± 110240.490.430.59
 Bread47 ± 3840 ± 57−130.660.670.8042 ± 2753 ± 77260.600.680.87
 Noodles85 ± 7197 ± 88150.530.520.9872 ± 4995 ± 72330.390.42
 Other cereals10 ± 1121 ± 341110.150.150.198 ± 1117 ± 241030.260.260.33
Potatoes and starches46 ± 3327 ± 21−410.290.320.4944 ± 3238 ± 29−130.090.250.39
Sugar9 ± 82 ± 4−800.360.250.308 ± 81 ± 4−820.070.060.07
Pulses102 ± 10697 ± 144−60.590.530.6672 ± 4467 ± 44−60.270.300.45
Nuts and seeds7 ± 113 ± 4−610.310.300.405 ± 73 ± 9−330.01−0.06−0.09
Vegetables403 ± 180218 ± 145−460.480.480.55354 ± 125245 ± 175−310.390.450.52
 Green and yellow vegetables194 ± 134110 ± 90−430.430.470.59170 ± 86114 ± 87−330.380.410.57
 White vegetables209 ± 102108 ± 96−480.530.500.68184 ± 75131 ± 128−290.390.410.57
  Pickled vegetables21 ± 5115 ± 21−320.430.370.4218 ± 2121 ± 50210.320.340.45
  Cruciferous vegetables91 ± 5954 ± 68−410.630.640.8287 ± 6455 ± 41−370.460.450.54
  Green, leafy vegetable43 ± 4320 ± 20−540.330.280.3738 ± 2321 ± 14−430.260.290.41
  Yellow vegetables128 ± 11378 ± 83−390.490.520.63105 ± 7379 ± 76−250.360.420.51
  Other vegetables121 ± 7354 ± 38−560.310.360.51109 ± 5571 ± 73−350.340.370.56
Fruits193 ± 160209 ± 18480.600.640.69184 ± 113255 ± 196380.400.550.63
 Citrus fruit49 ± 7581 ± 88670.460.460.5143 ± 49109 ± 1391530.230.180.20
 Other fruit143 ± 126126 ± 108−120.540.570.75140 ± 104144 ± 10330.310.490.85
Fungi18 ± 1711 ± 11−360.480.480.5723 ± 2214 ± 12−380.420.380.46
Algae15 ± 228 ± 7−430.180.170.2210 ± 109 ± 8−90.350.320.47
Fish and shellfish115 ± 5378 ± 66−320.400.470.6989 ± 4073 ± 60−180.440.350.57
Meats72 ± 4362 ± 57−150.430.480.7065 ± 3855 ± 35−170.350.260.36
 Processed meat13 ± 166 ± 8−520.460.450.6313 ± 157 ± 7−480.300.330.47
 Red meat40 ± 3042 ± 4350.360.410.7436 ± 2932 ± 23−110.450.360.53
 Poultry19 ± 2613 ± 18−300.250.250.3816 ± 1915 ± 13−50.270.220.36
Eggs36 ± 2332 ± 55−110.500.460.6733 ± 1925 ± 30−240.350.350.53
Milk and dairy products176 ± 147275 ± 305560.620.580.66174 ± 110257 ± 337480.700.620.76
 High-fat milk87 ± 9699 ± 157130.470.440.5095 ± 91120 ± 201260.640.590.69
 Low-fat milk89 ± 137177 ± 286980.620.560.6079 ± 83137 ± 207740.680.610.70
Fats and oils11 ± 612 ± 8120.400.350.4510 ± 612 ± 8240.380.520.73
 Butter2 ± 21 ± 2−490.320.340.502 ± 21 ± 4−120.350.350.56
 Margarine and oils9 ± 511 ± 8250.310.260.359 ± 611 ± 6310.290.420.57
Confectionaries29 ± 2823 ± 32−190.280.370.4537 ± 3037 ± 4610.340.320.43
 Japanese confectionery11 ± 158 ± 15−290.210.240.3315 ± 2315 ± 20−10.090.040.05
 Western confectionery18 ± 2415 ± 21−130.340.410.5021 ± 2122 ± 3220.260.240.32
Alcoholic beverages219 ± 276263 ± 281200.800.800.8876 ± 15190 ± 187190.650.570.60
Nonalcoholic beverages749 ± 772863 ± 699150.450.370.40617 ± 434888 ± 621440.330.330.35
 Green tea386 ± 738519 ± 427350.680.670.72246 ± 220603 ± 5601450.460.420.45
 Coffee176 ± 204199 ± 281130.810.800.84167 ± 175157 ± 155−60.820.820.88
 Other beverage210 ± 260144 ± 358−310.430.450.49268 ± 359128 ± 190−520.310.320.35
Seasonings and spices138 ± 10023 ± 15−830.040.080.10142 ± 11120 ± 14−86−0.28−0.31−0.36

MEDIAN   0.450.450.51   0.350.350.51

Abbreviation: SD, standard deviation.

aIntakes based on second FFQ, conducted in 2007–2008. bPercentage differences: (FFQ1 − DR)/DR * 100 (%). cSpearman’s rank correlation coefficients based on crude and energy-adjusted values. For men, r ≥ 0.24 = P < 0.05, r ≥ 0.31 = P < 0.01, r ≥ 0.39 = P < 0.001. For women, r ≥ 0.23 = P < 0.05, r ≥ 0.30 = P < 0.01, r ≥ 0.38 = P ≤ 0.001. dDeattenuated CCx = observed CCx * SQRT(1 + λx/n), where λx is the ratio of within- to between-individual variance for nutrient x, and n is number of dietary records; observed CCs were based on energy-adjusted values other than energy intake.

—: not applicable for calculation.

Abbreviation: SD, standard deviation. aIntakes based on second FFQ, conducted in 2007–2008. bPercentage differences: (FFQ1 − DR)/DR * 100 (%). cSpearman’s rank correlation coefficients based on crude and energy-adjusted values. For men, r ≥ 0.24 = P < 0.05, r ≥ 0.31 = P < 0.01, r ≥ 0.39 = P < 0.001. For women, r ≥ 0.23 = P < 0.05, r ≥ 0.30 = P < 0.01, r ≥ 0.38 = P ≤ 0.001. dDeattenuated CCx = observed CCx * SQRT(1 + λx/n), where λx is the ratio of within- to between-individual variance for nutrient x, and n is number of dietary records; observed CCs were based on energy-adjusted values other than energy intake. —: not applicable for calculation.

Joint classification by quintile

We conducted further analysis to compare FFQ1 with the 4d-DR based on joint classification by quintile. Most nutrients and food groups were classified into the opposite extreme categories by 5% or less of men or women, with a corresponding median value for men and women of 1% and 3%, respectively, for nutrients, and of 3% and 3%, respectively, for food groups (Supplemental Tables 1 and 2). In contrast, retinol for men and women showed a relatively high percentage of extreme categories by joint classification (6% and 12%, respectively) and a relatively low CC (0.32 and 0.11, respectively) and regression coefficient (0.18 and 0.15, respectively). Further, cryptoxanthin for women showed a relatively low percentage of the same and adjacent categories (53%) and a relatively low CC (0.07) and regression coefficient (0.05).

Reproducibility

We also examined the reproducibility of dietary intake estimated by 2 identical FFQs (FFQ0 and FFQ1) administered at an average interval of 2.7 years (range 1.3–4.0 years). CCs for nutrient intakes in the crude values varied from 0.54 for retinol to 0.80 for phosphorus (median r = 0.70) in men and from 0.48 for cholesterol and 0.72 for vitamin C (median r = 0.61) in women. With regard to the food groups, CC in the crude values varied from 0.35 for other cereals to 0.75 for coffee (median r = 0.64) in men and from 0.48 for red meat and 0.80 for coffee (median r = 0.63) in women (Supplemental Tables 3 and 4).

Percentage contributions of the top 20 foods to total energy

Finally, we conducted an additional analysis of the cumulative percentage contributions of the top 20 foods for energy, based on the 4d-DRs, to assess the foods listed in the FFQ. The cumulative percentage of the top 20 foods for energy was 44.0% and 41.0% for men and women, respectively (Supplemental Table 5).

DISCUSSION

We examined the validity of ranking middle-aged urban-dwelling cancer screenees in Japan by level of dietary intake using an FFQ, with 4-day DR data as the reference method. The FFQ was initially developed and validated in rural populations. As compared with reference intakes, differences in mean absolute consumption based on the FFQ varied and tended to be underestimated. However, using the FFQ, dietary assessment of many nutrients and food groups showed moderate validity and reproducibility in ranking urban residents, whose diet and lifestyle might differ from those of rural residents. In comparison with 4d-DRs corrected for intraindividual variance, for most nutrients, the validity of the FFQ was similar to or better than that observed in a comparison with 28-day weighed diet records among the rural residents for which the FFQ was developed.[6] In that initial validation study, median CCs for energy and 45 nutrients were 0.43 and 0.39 for men and women, respectively, and 0.38 and 0.32 for 19 main food groups. Evaluation of diet might be complicated by the apparently wider variety of foods eaten by urban as compared with rural residents in Japan (percent energy from cereal areas among the former was less than that among the latter[13]), as has been seen in China[14] and Morocco,[15] although we saw no large difference in the validity of intakes, as estimated by the FFQ, between urban and rural populations in the present study. Wakai[7] reviewed 21 validation studies of FFQs developed in Japan and reported a median CC for energy intake of 0.46 (range 0.20 to 0.87) and a median CC among the 21 studies ranging from 0.22 (n-6 PUFA) to 0.58 (calcium) for energy and 24 nutrients. As compared with the median CCs among the 21 studies for energy and 24 nutrients and 17 food groups, the CCs for the many nutrients and food groups evaluated in the present study were not substantially different or higher.[7] Attenuation caused by measurement error may be unavoidable in studies that use FFQs to investigate diet–disease associations. For example, based on a true relative risk of 2.0, if the regression coefficient of intakes according to an FFQ and DR varies from 0.6 to 0.2, the corresponding relative risk is further attenuated from 1.52 to 1.15.[1] A similar attenuation might be unavoidable in any examination that uses the present FFQ to assess diet–disease associations. Further investigation will be needed to examine the effects of measurement error on diet–disease associations in an actual dataset. The CC for energy intake among women in this study (deattenuated CC: r = 0.34) was lower than the median of 21 previous studies. Further, the CCs of intakes based on the FFQ appeared to be lower in women than in men for most of the energy and nutrients examined (median deattenuated CC: 0.57 and 0.47 for men and women, respectively). This lower correlation in women than men has been previously observed in Japanese and Western populations.[7],[16] Sex differences in validity might be partly due to disparities in the ease of response to the structured questionnaire that result from differences between men and women in their interest in dietary habits.[4] Moreover, we also found that the cumulative percentage among the top 20 foods for energy was lower for women than for men and that it was also lower than among subjects during the development of the initial FFQ (men: 63.9%, women: 56.3%).[17] These results suggest that the lower validity for energy intake among women is partly attributable to a lower contribution to energy by individual foods in women than in men, as was seen among subjects during the development of the initial FFQ. Our study has several potential limitations. First, the response rate was not necessarily high, although the participants were randomly chosen and recruited from among cancer screenees. Selection bias, eg, a higher proportion of health-conscious subjects than in the actual population, was likely present, and thus the possibility of overestimating the validity of the FFQ cannot be ruled out. This response rate is nevertheless reasonable considering the burden posed by studies such as this. Second, reference intakes were based on 4-day values, versus the 28-day values used for the initial validation study of the FFQ.[4]–[6] A simple comparison of CCs might have been difficult, even though the present CCs were corrected for intraindividual variance. Moreover, although the dietary records were completed on consecutive days (ie, in the same season), the FFQ inquired about the previous year. In addition, responses to the FFQ might have depended on the season,[18] and FFQ1 was conducted in the season during which the dietary record was done. Thus, the possibility that validity might have been overestimated cannot be ruled out, especially for seasonal foods such as fruit and vegetables. Third, in the examination of reproducibility, we were unable to consider the “true” change in diet. Although we would have liked to examine the effects of random variation in response to the FFQ, the effects of such variation and the “true” change of diet could not be readily separated, and both might have attenuated the reproducibility of the FFQ.[1] Therefore, the reproducibility of this FFQ (in random variation in response) might have been underestimated. In general, the advantages of FFQ-based dietary assessment are that the burden on participants is not heavy, an interviewer is unnecessary, costs are relatively low,[19] and the long-term diet can be ranked. In the present study, too, the median percentages of extreme categories based on joint classification by quintile between FFQ and DR for nutrients and food groups were 1% and 3%, indicating that this FFQ is suitable for the ranking of individuals with regard to intakes of many nutrients and food groups in large-scale studies of urban populations. However, some nutrient and food group intakes estimated by this FFQ showed relatively low CCs and regression coefficients; thus, any application of this FFQ to the examination of diet–disease associations, such as investigations of retinol and cryptoxanthin, must carefully address the problem of classification. In conclusion, these results indicate that the present FFQ, which was initially developed for rural populations, provides reasonably valid measures in ranking middle-aged cancer screenees in urban areas in Japan according to level of consumption of many nutrients and food groups. Abbreviations: SFA, saturated fatty acid; MUFA, monounsaturated fatty acid; PUFA, polyunsaturated fatty acid; Eq, equivalent. aJoint classification for energy intake was calculated by using crude values. Abbreviations: SFA, saturated fatty acid; MUFA, monounsaturated fatty acid; PUFA, polyunsaturated fatty acid; Eq, equivalent. For men, r ≥ 0.24 = P < 0.05, r ≥ 0.31 = P < 0.01, r ≥ 0.39 = P < 0.001. For women, r ≥ 0.23 = P < 0.05, r ≥ 0.30 = P < 0.01, r ≥ 0.38 = P ≤ 0.001. For men, r ≥ 0.24 = P < 0.05, r ≥ 0.31 = P < 0.01, r ≥ 0.39 = P < 0.001. For women, r ≥ 0.23 = P < 0.05, r ≥ 0.30 = P < 0.01, r ≥ 0.38 = P ≤ 0.001.
Supplementary Table 1.

Comparison of food frequency questionnaire 1 (FFQ1) with 4-day diet record for energy-adjusted nutrients, based on joint classification by quintile (%)

 Men (n = 69)Women (n = 74)


 SamecategorySame andadjacentcategoryExtremecategorySamecategorySame andadjacentcategoryExtremecategory
Energy35711a28645a
Protein3577123601
Total fat2861131704
 SFA3565626655
 MUFA2259431680
 PUFA3067028624
  n-3 PUFA2659327583
  n-6 PUFA3873026665
 Cholesterol2567128624
Carbohydrate4470130734

 Total dietary fiber3978126691
  Water soluble3580131701
  Water insoluble3384024641

Sodium3668332571
 Salt equivalent3668327611
Potassium3875039781
Calcium2873030680
Magnesium3973037651
Phosphorus3577035701
Iron3680131723
Zinc3874123613
Copper3680024651
Manganese2867331694

Retinol33626236212
Retinol Eq2862926624
α-carotene3868337700
β-carotene3365635700
Cryptoxanthin3378318534
Lycopene3875431705
β-carotene Eq3367428721
Vitamin D3675122583
α-tocopherol2961122693
β-tocopherol2067419574
γ-tocopherol2868320688
δ-tocopherol4280018684
Vitamin K3283027730
Vitamin B12974132643
Vitamin B23065426700
Niacin3065327645
Vitamin B63367141690
Vitamin B122265430653
Folate3270026664
Pantothenic acid4578142730
Vitamin C3987026680

Daidzein3081027761
Genistein3280031701

MEDIAN3370128683

Abbreviations: SFA, saturated fatty acid; MUFA, monounsaturated fatty acid; PUFA, polyunsaturated fatty acid; Eq, equivalent.

aJoint classification for energy intake was calculated by using crude values.

Supplementary Table 2.

Comparison of food frequency questionnaire 1 (FFQ1) with 4-day diet record for energy-adjusted food groups based on joint classification by quintile (%)

 Men (n = 69)Women (n = 74)


 SamecategorySame andadjacentcategoryExtremecategorySamecategorySame andadjacentcategoryExtremecategory
Cereals2670032684
 Rice3071342723
 Bread3080041760
 Noodles2968037725
 Other cereals1952424555
Potatoes and starches3067120643
Sugar2657316557
Pulses3874330623
Nuts and seeds26580155410
Vegetables2670127733

 Green and yellow vegetables4568427700
 White vegetables2577127681
  Pickled vegetables3068430685

  Cruciferous vegetables4280131641
  Green, leafy vegetable2867627611
  Yellow vegetables3077327731
  Other vegetables1964128654
Fruits4981138730
 Citrus fruit3677323605
 Other fruit3677130691
Fungi3371324623
Algae3358622643
Fish and shellfish2871123613

Meats3878628667
 Processed meat2867132723
 Red meat2971632621
 Poultry2561328545
Eggs3674126613
Milk and dairy products4178335780
 High-fat milk4167442873
 Low-fat milk3678342823
Fats and oils3061439720
 Butter3264634705
 Margarine and oils2961434661
Confectionaries2067128623
 Japanese confectionery2264414555
 Western confectionery3265024605
Alcoholic beverages4691042720
Nonalcoholic beverages2664122653
 Green tea4880027650
 Coffee4593050910
 Other beverage2968026654
Seasonings and spices16494164212

MEDIAN3068328653
Supplementary Table 3.

Spearman rank correlation coefficients between 2 food frequency questionnaires, administered at an average interval 2.7 years, for estimated nutrient intakes

 Men (n = 69)Women (n = 75)


 CrudeEnergy-adjustedCrudeEnergy-adjusted
Energy0.720.59
Protein0.760.650.590.55
Total fat0.730.510.620.40
 SFA0.750.540.660.55
 MUFA0.710.470.620.41
 PUFA0.680.620.540.44
  n-3 PUFA0.640.520.630.59
  n-6 PUFA0.680.590.520.42
 Cholesterol0.760.500.480.46
Carbohydrate0.650.770.570.43

 Total dietary fiber0.700.740.620.66
  Water soluble0.650.650.620.62
  Water insoluble0.700.750.640.64

Sodium0.710.520.660.58
 Salt equivalent0.710.520.660.59
Potassium0.730.740.650.76
Calcium0.770.720.620.56
Magnesium0.730.750.610.74
Phosphorus0.800.740.610.51
Iron0.700.660.610.69
Zinc0.710.650.580.67
Copper0.650.690.590.70
Manganese0.720.750.690.70

Retinol0.540.390.490.48
Retinol Eq0.610.450.530.44
α-carotene0.650.600.680.63
β-carotene0.680.640.680.67
Cryptoxanthin0.680.640.640.72
Lycopene0.590.520.490.37
β-carotene Eq0.680.640.690.67
Vitamin D0.630.430.670.54
α-tocopherol0.630.530.580.58
β-tocopherol0.670.540.520.41
γ-tocopherol0.640.510.510.46
δ-tocopherol0.680.640.590.58
Vitamin K0.650.670.550.58
Vitamin B10.740.610.590.51
Vitamin B20.740.620.670.67
Niacin0.710.500.670.55
Vitamin B60.720.540.650.66
Vitamin B120.690.570.660.56
Folate0.700.690.670.77
Pantothenic acid0.710.760.610.69
Vitamin C0.780.760.720.77

Daidzein0.610.630.600.58
Genistein0.610.630.600.58

MEDIAN0.700.630.610.58

Abbreviations: SFA, saturated fatty acid; MUFA, monounsaturated fatty acid; PUFA, polyunsaturated fatty acid; Eq, equivalent.

For men, r ≥ 0.24 = P < 0.05, r ≥ 0.31 = P < 0.01, r ≥ 0.39 = P < 0.001. For women, r ≥ 0.23 = P < 0.05, r ≥ 0.30 = P < 0.01, r ≥ 0.38 = P ≤ 0.001.

Supplementary Table 4.

Spearman rank correlation coefficients between 2 food frequency questionnaires, administered at an average interval 2.7 years, for estimated food-group intakes

 Men (n = 69)Women (n = 75)


 CrudeEnergy-adjustedCrudeEnergy-adjusted
Cereals0.630.690.490.55
 Rice0.640.620.650.63
 Bread0.730.700.550.60
 Noodles0.640.600.490.51
 Other cereals0.350.380.650.64
Potatoes and starches0.600.600.650.60
Sugar0.740.680.650.50
Pulses0.450.510.650.56
Nuts and seeds0.420.320.630.60
Vegetables0.630.630.700.64
 Green and yellow vegetables0.640.580.610.51
 White vegetables0.690.620.690.62
  Pickled vegetables0.740.700.760.67
  Cruciferous vegetables0.650.600.500.46
  Green, leafy vegetables0.570.530.570.61
  Yellow vegetables0.600.550.600.46
  Other vegetables0.710.650.700.58
Fruits0.700.670.630.69
 Citrus fruit0.670.610.620.66
 Other fruit0.660.640.610.55
Fungi0.730.750.600.60
Algae0.650.650.570.56
Fish and shellfish0.620.390.700.62
Meats0.690.570.540.52
 Processed meat0.670.620.710.70
 Red meat0.630.530.480.47
 Poultry0.540.360.500.49
Eggs0.660.530.500.51
Milk and dairy products0.730.690.610.52
 High-fat milk0.490.450.710.66
 Low-fat milk0.680.650.500.52
Fats and oils0.630.530.630.51
 Butter0.570.450.630.55
 Margarine and Oils0.610.540.640.51
Confectionaries0.630.600.630.64
 Japanese0.560.570.600.62
 Western0.660.620.600.55
Alcoholic beverages0.860.860.760.68
Non-alcoholic beverages0.610.610.680.63
 Green tea0.680.660.750.67
 Coffee0.750.690.800.76
 Other beverage0.450.480.560.52
Seasonings and spices0.690.700.530.48

MEDIAN0.640.610.630.58

For men, r ≥ 0.24 = P < 0.05, r ≥ 0.31 = P < 0.01, r ≥ 0.39 = P < 0.001. For women, r ≥ 0.23 = P < 0.05, r ≥ 0.30 = P < 0.01, r ≥ 0.38 = P ≤ 0.001.

Supplementary Table 5.

Cumulative percentage contribution of the top 20 foods to energy intake, as assessed by 4-day diet record

CodeFoodkcal/dayCumulative percent
Men (n = 69)   
1088Rice, Paddy rice grain, Well-milled rice422.918.6
1026Breads, White table bread61.121.3
16006Fermented alcoholic beverages, Beer, pale52.823.6
12004Hen’s eggs, whole, raw51.025.9
13003Liquid milks, Ordinary liquid milk49.528.0
1085Rice, Paddy rice grain, Brown rice45.830.1
14006Fats and oils, Vegetable oil, blend44.732.0
4046Natto (Fermented soybean), Itohiki-natto31.733.4
1048Chinese noodles, Wet form, boiled28.834.7
16015Distilled alcoholic beverages, Shochu, 25% alcohol25.235.8
13025Yogurt, Whole milk, unsweetened24.036.9
1087Rice, Paddy rice grain, Under-milled rice22.837.9
1039Udon, Wet form, boiled20.838.8
7107Bananas, Raw fruit19.239.6
11221Chicken, Broiler meats, Thigh, with skin, raw18.240.4
3003Sugars, Soft sugars, White17.641.2
1064Macaroni, spaghetti, Dry form, boiled16.241.9
2017Potatoes, Tuber, raw16.142.6
11123Pork, large breeds, Loin, lean and fat, raw16.143.3
4032Tofu (soybean curd), Momen-tofu15.744.0
Women (n = 74)   
1088Rice, Paddy rice grain, Well-milled rice286.015.5
1026Breads, White table bread67.919.2
13003Liquid milks, Ordinary liquid milk54.322.2
12004Hen’s eggs, whole, raw46.824.7
14006Fats and oils, Vegetable oil, blend36.426.7
1048Chinese noodles, Wet form, boiled28.628.2
1085Rice, Paddy rice grain, Brown rice21.129.4
4046Natto (Fermented soybean), Itohiki-natto20.930.5
1089Rice, Paddy rice grain, Well-milled rice with germ19.131.6
2017Potatoes, Tuber, raw17.932.5
4040Abura-age (Fried thin slices of pressed tofu, soybean curd)17.333.5
1039Udon, Wet form, boiled17.234.4
13025Yogurt, Whole milk, unsweetened16.635.3
7148Apples, Raw fruit15.836.2
16006Fermented alcoholic beverages, Beer, pale15.737.0
15098Biscuits, soft, Western-style confectioneries15.337.8
11221Chicken, Broiler meats, Thigh, with skin, raw14.838.6
14001Fats and oils, Olive oil14.439.4
1117Glutinous rice products, Rice cake14.140.2
7107Bananas, Raw fruit14.141.0
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