Table 1.

Description of 10,092 participants included in the present study.

Dietary Ca intake	Total	Q1	Q2	Q3	Q4	Q5	P value
Age (years)	13.56 ± 3.42	14.27 ± 3.39	13.54 ± 3.42	13.20 ± 3.42	13.00 ± 3.39	13.87 ± 3.33	<0.0001
Sex (%)							<0.0001
Male	5766 (57.14%)	46.21	49.37	51.74	60.80	72.62
Female	4326 (42.86%)	53.79	50.63	48.26	39.20	27.38
Race/ethnicity (%)							<0.0001
White	6203 (61.47%)	52.64	55.92	58.97	65.43	70.91
Black	1471 (14.57%)	21.86	17.34	15.26	12.62	8.17
Mexican American	1146 (11.36%)	10.44	10.90	12.97	11.96	10.51
Other	1272 (12.61%)	15.05	15.83	12.80	9.98	10.41
BMI (kg/m2)	22.04 ± 5.57	23.20 ± 6.10	22.26 ± 5.97	21.83 ± 5.47	21.53 ± 5.21	21.64 ± 5.07	<0.0001
Income poverty ratio	2.52 ± 1.56	2.20 ± 1.51	2.45 ± 1.56	2.47 ± 1.55	2.59 ± 1.54	2.77 ± 1.59	<0.0001
Physical activity (%)							<0.0001
Not walk very much	307 (3.05%)	5.13	3.98	2.89	1.98	1.88
Walk a lot	651 (6.45%)	9.97	6.07	6.44	4.83	5.70
Climb stairs or hills often	491 (4.87%)	6.16	4.79	3.23	4.55	5.70
Weight bearing activity	1364 (13.50%)	14.20	13.12	11.09	11.59	17.07
Not recorded	7279 (72.13%)	64.54	72.04	76.35	77.04	69.72
Calcium supplement use (%)							<0.0001
No	8625 (85.46%)	89.39	87.12	84.91	82.95	83.97
Yes	1468 (14.54%)	10.61	12.88	15.09	17.05	16.03
Serum Ca (mg/dL)	9.71 ± 0.25	9.69 ± 0.28	9.71 ± 0.25	9.70 ± 0.24	9.72 ± 0.24	9.74 ± 0.26	<0.0001
Total BMD (g/cm2)	1.00 ± 0.16						<0.0001
8 to 11 years	0.84 ± 0.08	0.83 ± 0.09	0.83 ± 0.08	0.84 ± 0.08	0.85 ± 0.08	0.85 ± 0.07
12 to 15 years	1.01 ± 0.11	1.00 ± 0.11	1.00 ± 0.10	1.01 ± 0.10	1.01 ± 0.11	1.02 ± 0.11
16 to 19 years	1.14 ± 0.11	1.13 ± 0.10	1.13 ± 0.11	1.13 ± 0.10	1.15 ± 0.11	1.16 ± 0.11

Mean ± s.d. for continuous variables: P value was calculated by weighted linear regression model. % for Categorical variables: P value was calculated by weighted chi-square test.