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General characteristic of the study population and distribution of the samples are outlined in Table 1. A total of 28, 250 children and adolescents aged 6-17 years old were included in this analysis, with 14, 168 boys (50.2%) and 14, 082 girls (49.8%) after data cleaning. Samples of the four age groups (6-8, 9-11, 12-14, and 15-17) were 6, 523/23.1%, 7, 090/25.1%, 7, 585/26.9%, and 7, 052/25.0%, respectively. Proportions of the five household income levels were significantly different, among which the proportion of household incomes of 5, 000-9, 999 CNY was highest (24.6%) and of 15, 000-19, 999 CNY lowest (12.0%).
Sample Characteristics Sample Size, n(%) Dairy Consumption Frequency, n(%) Z/H Value (P Value) 0/week ≤ 1/week 2-6/week ≥ 1/day Total dairy 28, 250 (100.0) 3, 568 (12.6) 4, 095 (14.5) 10, 380 (36.7) 10, 207 (36.1) Gender 0.7521 (0.4520)* Boys 14, 168 (50.2) 1, 914 (13.5) 2, 016 (14.2) 5, 059 (35.7) 5, 179 (36.6) Girls 14, 082 (49.8) 1, 654 (11.7) 2, 079 (14.8) 5, 321 (37.8) 5, 028 (35.7) Age (y) 147.0331 (< 0.0001)# 6-8 6, 523 (23.1) 740 (11.3) 779 (11.9) 2, 401 (36.8) 2, 603 (39.9) 9-11 7, 090 (25.1) 840 (11.8) 924 (13.0) 2, 615 (36.9) 2, 711 (38.2) 12-14 7, 585 (26.9) 1, 004 (13.2) 1, 254 (16.5) 2, 701 (35.6) 2, 626 (34.6) 15-17 7, 052 (25.0) 984 (14.0) 1, 138 (16.1) 2, 663 (37.8) 2, 267 (32.1) Residential area 3431.0373 (< 0.0001)# Large city 6, 785 (24.0) 357 (5.3) 402 (5.9) 2, 033 (30.0) 3, 993 (58.9) Small-medium city 8, 131 (28.8) 886 (10.9) 829 (10.2) 3, 209 (39.5) 3, 207 (39.4) General rural area 8, 353 (29.6) 1, 186 (14.2) 1, 542 (18.5) 3, 379 (40.5) 2, 246 (26.9) Poor rural area 4, 981 (17.6) 1, 139 (22.9) 1, 322 (26.5) 1, 759 (35.3) 761 (15.3) Annual family income (CNY)a 1035.3793 (< 0.0001)# < 5, 000 4, 473 (21.2) 935 (20.9) 912 (20.4) 1, 552 (34.7) 1, 074 (24.0) 5, 000-9, 999 5, 196 (24.6) 748 (14.4) 962 (18.5) 1, 936 (37.3) 1, 550 (29.8) 10, 000-14, 999 4, 390 (20.8) 478 (10.9) 597 (13.6) 1, 668 (38.0) 1, 647 (37.5) 15, 000-19, 999 2, 539 (12.0) 232 (9.1) 267 (10.5) 1, 004 (39.5) 1, 036 (40.8) ≥ 20, 000 4, 530 (21.4) 385 (8.5) 354 (7.8) 1, 604 (35.4) 2, 187 (48.3) Fluid milk 28, 249 (100.0) 11, 752 (41.6) 3, 425 (12.1) 6, 725 (23.8) 6, 347 (22.5) Yogurt 28, 224 (100.0) 8, 455 (29.9) 7, 695 (27.2) 8, 260 (29.2) 3, 834 (13.6) Note.^Values are number (percentage) unless otherwise indicated; aThe sample size with completed frequency and income information was 21, 128; *Z value for the Wilcoxon Test; #H value for the Kruskal-Wallis H Test; CNY, China Yuan. Table 1. Characteristics across Categories of Frequencies of Dairy Consumption^
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Of the children and adolescents enrolled, 36.1% consumed total dairy food more than once per day (≥ 1/day), with decreased seen with age. This proportion in large cities, small-medium cities, general rural areas and poor rural areas were 58.9%, 39.4%, 26.9%, and 15.3%, respectively (P < 0.05). This proportion in the five income levels (< 5, 000, 5, 000-9, 999, 10, 000-14, 999, 15, 000-19, 999, and ≥ 20, 000) were 24.0%, 29.8%, 37.5%, 40.8%, and 48.3%, respectively (P < 0.05). Approximately 12.6% children did not consume dairy food (0/week). No significant differences were observed in dairy food consumption frequency between boys and girls (Table 1).
Children who consumed fluid and yogurt more than once per day (≥ 1/day) was 22.5% and 13.6%, respectively. About 41.6% children did not consume fluid milk and 29.9% children didn't consume yogurt (Table 1).
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The average quantity of dairy consumption was 126.7 g/day in Chinese children and adolescents aged 6-17. Children who consumed more than 300 g/day of dairy food were 9.4%. The proportion of children consuming this level of dairy food was 18.8% in large cities and 2.7% in poor rural areas. The proportions of children consuming more than 200 g/day of dairy food were 29.9%, 27.5%, 25.7%, and 24.4% in the four age groups (6-8, 9-11, 12-14, and 15-17) and 44.9%, 29.7%, 18.8%, and 11.0% in the four area types (the large city, small-medium city, general rural area and poor rural area) (P < 0.05). These proportions increased with average annual household income (P < 0.05) (Table 2).
Sample Characteristics Sample Size, n(%) Amount (g) n (%) by Distribution of Dairy Consumption Amounts Z/H Value (P Value) 0g 1-99 g 100-199 g 200-299 g ≥300g Total dairy 28, 210(100.0) 126.7 3, 568(12.6) 11, 532 (40.9) 5, 544 (19.7) 4, 918 (17.4) 2, 648 (9.4) Gender 0.4311(0.6664)* Boys 14, 114(50.1) 128.2 1, 914(13.5) 5, 645(39.9] 2, 694(19.0) 2, 550(18.0) 1, 341 (9.5) Girls 14, 066 (49.9) 125.2 1, 654(11.8) 5, 887 (41.9) 2, 850(20.3) 2, 368(16.8) 1, 307(9.3) Age (y) 69.4352 (< 0.0001)# 6-8 6, 509 (23.1) 135.1 740(11.4) 2, 544(39.1) 1, 277(19.6) 1, 343(20.6) 605 (9.3) 9-11 7, 088 (25.1) 127.8 840(11.9) 2, 809(39.6) 1, 486(21.0) 1, 328(18.7) 625 (8.8) 12-14 7, 572 (26.8) 124.6 1, 004(13.3) 3, 169 (41.9) 1, 453 (19.2) 1, 234(16.3) 712(9.4) 15-17 7, 041 (25.0) 122.9 984(14.0) 3, 010 (42.7) 1, 328(18.9) 1, 013(14.4) 705(10.0) Residential area 3082.6510 (< 0.0001)# Large city 6, 770(24.0) 190.1 357(5.3) 1, 819(26.9) 1, 557(23.0) 1, 766(26.1) 1, 271 (18.8) Small-medium city 8, H7 (52.8) 138.5 886 (10.9) 3, 030(37.3) 1, 790(22.1) 1, 593(19.6) 818(10.1) General rural area 8, 344(29.6) 99.8 1, 186(14.2) 3, 994 (47.9) 1, 591(19.1) 1, 147(13.7) 426(5.1) Poor rural area 4, 979 (17.6) 66.2 1, 139(22.9) 2, 689 (54.0) 606(12.2) 412(8.3) 133(2.7) Annual family income (CNY)a 815.3618 (< 0, 0001)# < 5, 000 4, 469 (21.2) 93.1 935 (20.9) 2, 050 (45.9) 632(14.1) 567(12.7) 285 (6.4) 5, 000-9, 999 5, 192 (24.6) 107.8 748 (14.4) 2, 416(46.5) 883(17.0) 785 (15.1) 360 (6.9) 10, 000-14, 999 4, 385 (20.8) 129.6 478 (10.9) 1, 811(41.3) 842(19.2) 887 (20.2) 367 (8.4) 15, 000-19, 999 2, 533 (12.0) 139.7 232(9.2) 968 (38.2) 558(22.0) 514(20.3) 261(10.3) ≥20, 000 4, 518(21.4) 160.1 385 (8.5) 1, 482(32.8) 1, 048(23.2) 979(21.7) 624(13.8) Fluid milk 28, 249 (100.0) 76.4 11, 752 (41.6) 7, 867(27.8) 3, 382 (12.0) 4, 455(15.8) 793 (2.8) Yogurt 28, 244(100.0) 45.8 8, 455(29.9) 15, 156(53.7) 2, 915(10.3) 1, 443 (5.1) 275 (1.0) Note. ^Values are number (percentage) unless otherwise indicated; aThe sample size with completed amount and income information was 21, 097; *Z value for the Wilcoxon Test; #H value for the Kruskal-Wallis H Test; CNY, China Yuan. Table 2. Characteristics across Categories of Amount of Dairy Consumption^
The average quantity of fluid milk and yogurt were only 76.4 g/day and 45.8 g/day in Chinese children and adolescents (Table 2).
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The proportions for stunting and wasting children were 2.2% and 7.6% in Chinese children and adolescents, respectively, with higher proportions in boys (2.4% and 8.8%) than in girls (2.0% and 6.4%) (P < 0.05). The 15-17 years old group had the highest stunting and wasting percentage with 2.9% and 8.1%, respectively (P < 0.05). The stunting and wasting proportions decreased with the development of cities and the increase of income level (P < 0.05). Proportions of stunting and wasting both decreased with the dairy consumption frequency (P < 0.05). These two proportions with a consumption of '≥ 1 /day' were 1.6% and 6.5%, while that with no dairy consumption ('0/week') were 3.9% and 9.3%. These trends in the quantity were almost the same as that in frequency (P < 0.05) (Table 3).
Table 3. Nutritional Characteristics of the Different Study Groups^
After adjustment for area, age, residential area development, average annual household income, consumption frequency of grains, meat and eggs, status of physical activity and sedentary time, dairy consumption frequency was negatively associated with stunting and wasting for boys, and only with stunting for girls. The relative risk (OR with 95% confidence interval) of stunting with total dairy consumption frequency of ≥ 1/day among boys was 0.616 (0.417-0.912) compared to 0/week. The relative risk of wasting was 0.738 (0.590-0.924) among boys in the ≥ 1/day frequency group. For the frequency of 2-6/week group and the quantity of 1-99 g group among girls, the relative risk of stunting was 0.570 (0.376-0.862) and 0.560 (0.379-0.830). There were no significant association between wasting and total dairy consumption among girls (Table 4).
Table 4. Association between Total Dairy Consumption and Nutrition Status in Boys and Girls^
For boys, the consumption frequency of fluid milk was negatively associated with stunting, and the relative risk of stunting with consumption frequency of fluid milk of 2-6/week was 0.663 (0.461-0.951) comparing to 0/week (Supplementary Table 1 available in www.besjournal.com). The consumption of yogurt was negatively with stunting for girls, and with wasting for boys (Supplementary Table S2 available in www.besjournal.com).
Table Supplementary Table 1. Association between Fluid Milk Consumption and Nutrition Status in Boys and Girls^
Table Supplementary Table 2. Association between Yogurt Consumption and Nutrition Status in Boys and Girls^
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Of this study population of children, 10.7% were overweight and 5.9% obese. The proportion of boys who were overweight (12.6%) or obese (7.8%) were both higher than that of girls who were overweight (8.8%) or obese (4.0%) (P < 0.05). In the 9-11 age group, 12% were overweight, which was the most within the four age groups (6-8, 9-11, 12-14, and 15-17). The highest proportion of obesity was 9.6% and within the 6-8 age group. As the development of cities expanded and income of families increased, the proportion of overweight and obese children rose (P < 0.05). The proportion of obese children went up with the frequency of dairy food consumption. Obesity proportions within the four age groups for dairy consumption frequency were 5.1%, 5.2%, 5.6%, and 6.8%, and that of the five quantity groups were 5.1%, 5.4%, 6.4%, 6.5%, and 6.8% (P < 0.05). The overweight proportion with quantity followed the same trend (Table 3).
Logistic regression analysis showed that the association between total dairy consumption and obesity among boys and girls were significant after controlling for area, age, residential area development, average annual household income, consumption frequency of grains, meat and eggs, status of physical activity and sedentary time. The relative risk of obesity with the consumption quantity of 200-299 g in boys were 0.738 (0.555-0.981), and the relative risk of obesity with the consumption quantity of ≥ 300 g in girls was 0.561 (0.350-0.899) (Table 4). Similar relationship were found in the consumption of fluid milk in girls (Supplementary Table S1). There was no significant association between dairy consumption with overweight.