Objective: To investigate the nutritional status of vitamin D (VD) and its influencing factors under different doses of vitamin D supplementation for infants in Chongqing

so as to provide reference for rational supplementation of VD. Methods: A total of 751 healthy infants and young children (from 0 to 3 years old) from 5 hospitals in different economic levels of Chongqing were selected

and the serum 25-hydroxyvitamin D (25(OH)D) levels were detected by questionnaire survey. According to different doses of vitamin D supplementation

age

season

feeding methods and other groups

the impacts of the above factors on 25(OH)D were investigated. Results: The VD supplement rate of infants aged from 0 to 3 years old was 74.6% (560/751)

and the preventive dose of VD was from 30 to 1

600 IU/d. The 25(OH)D level was (35.29±10.39) ng/mL

and increased firstly and then remained stable with the increase of VD supplementation. The 25(OH)D level was (30.51±11.03) ng/mL in children without supplementation

significantly lower than that in children with supplementation. The VD insufficiency and deficiency rate of the no-supplementation group was 14.7%

significantly higher than that in the supplementation group (P<0.05). The VD deficiency and inficiency rate of the high-dose supplementation group (>600 IU/d) was significantly lower than that in other groups (P<0.05). Different preventive dose

season

age and feeding method could affect the 25(OH)D level. Children without supplementation from food in winter and spring had the lowest 25(OH)D level of (18.44±11.91) ng/mL. Conclusion: The VD supplementation rate of children from 0 to 3 years old is relative high in Chongqing

however

there is a great variation in dose of daily supplementation. Preventive VD supplementation is an essential measure to maintain the normal 25(OH)D level. Season and feeding method can significantly affect the nutritional status of VD