Table 2

Mean values of adjusted lung function measurements across quintiles of vitamin A, carotene and vitamin C intake

	Q1	Q2	Q3	Q4	Q5	Difference between Q5 and Q1 (95% CI)	P values for trend
Vitamin A
Mean intake (μg RE)	151.2	353.6	573.1	893.9	2140.8
FEV₁ (mL)	2379	2389	2410	2397	2409	30 (10 to 50)	0.008
FVC (mL)	3119	3136	3158	3148	3152	33 (10 to 57)	0.007
Predicted FEV₁ (%)	91.37	91.44	91.91	91.45	91.94	0.57 (-0.08 to 1.22)	0.185
Predicted FVC (%)	90.93	91.06	91.45	91.22	91.48	0.55 (0.00 to 1.10)	0.195
Carotene
Mean intake (μg)	691.1	1747.4	2938.9	4736.1	11 574.1
FEV₁ (mL)	2347	2363	2376	2370	2379	32 (12 to 52)	0.010
FVC (mL)	3088	3117	3127	3119	3124	36 (13.59)	0.005
Predicted FEV₁ (%)	91.55	92.03	92.26	91.85	92.31	0.76 (0.12 to 1.39)	0.096
Predicted FVC (%)	91.02	91.68	91.78	91.41	91.82	0.80 (0.26 to 1.33)	0.015
Vitamin C
Mean intake (mg)	24.2	53.6	84.2	128.8	268.9
FEV₁ (mL)	2411	2423	2436	2441	2453	36 (16.56)	<0.001
FVC (mL)	3117	3122	3132	3140	3154	35 (12.58)	0.014
Predicted FEV₁ (%)	91.3	91.5	91.9	91.99	92.21	0.91 (0.27 to 1.55)	0.050
Predicted FVC (%)	91.29	91.33	91.58	91.77	92.0	0.71 (0.17 to 1.26)	0.118

Data were adjusted for age, sex, body mass index, energy intake, number of comorbid diseases, alcohol consumption, place of residence smoking history, pack-years (smoking amount), household income and education level. P values were determined using tests for linear trends across increasing quintiles (means) of antioxidant vitamin intake.
FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 s; RE, retinol equivalent; Q1, lowest quintile; Q5, highest quintile.