title: Sunlight Exposure and Vitamin D Status in Breastfed Infants.
abstract: OBJECTIVE
  To correlate the sunlight exposure in first 6 months to vitamin D status at 6 months of age in predominantly breastfed infants; and to quantify the sunlight exposure required to achieve serum 25(OH)D level >20 ng/mL, by 6 months of age.
  
  
  METHODS
  Design: Prospective cohort.
  
  
  METHODS
  Tertiary-care hospital predominantly catering to urban poor population in Delhi.
  
  
  METHODS
  132 healthy infants, delivered at term, and predominantly breastfed were enrolled at 6-8 weeks of age. Of these, 100 infants were available for final evaluation at 6 months of age (mean (SD) follow-up: 126 (17) days).
  
  
  METHODS
  Baseline maternal vitamin D (serum 25(OH)D) levels were obtained at enrolment. The mothers were asked to maintain a daily record of duration of sunlight exposure, timing of exposure, and body surface area exposed, for the infant, on a pre-designed proforma, till the child was 6 months of age. Infant's serum 25(OH)D was measured at 6 months of age.
  
  
  METHODS
  Cumulative Sun Index was calculated as a composite measure of overall duration/time/body surface area exposed to sunlight; and correlated with the infant serum 25(OH)D after adjusting for baseline maternal serum 25(OH)D levels, season of exposure, and skin color of the infant. Sun index for exposure in morning (before 10 am) and afternoon (10 am-3 pm) were also correlated to vitamin D status.
  
  
  RESULTS
  Of 100 mother-infant pairs completing the study, 90 mothers had vitamin D deficiency (serum 25(OH)D <12 ng/mL). The median duration of exposure of infants to sunlight was 17 min per week, on 6% of body surface area. Vitamin D levels of 67 (67%) infants at 6 months were less than 12 ng/mL and another 23% had insufficient levels (12-20 ng/mL). Cumulative sun index correlated positively to infant's serum 25(OH)D level at 6 months of age (r= 0.461, P<0.001). Increment in afternoon sun index by 1 unit increased the serum 25(OH)D level by 1.07 ng/mL (95% CI 0.37, 1.78; P= 0.003). A minimum 30 minute weekly afternoon sunlight exposure, between 10 am and 3 pm, over 40% body area (infant clothed in diapers, in prone position) for at least 16 weeks, was estimated requirement to achieve sufficient vitamin D levels (>20 ng/mL) by 6 months of age.
  
  
  CONCLUSIONS
  There is a significant positive correlation between afternoon sunlight exposure and infant's vitamin D levels, independent of maternal vitamin D status. Randomized controlled trials are suggested to explore the effectiveness of this simple intervention to prevent or treat vitamin D deficiency in children.
authors.affiliation: Departments of Pediatrics, #Biostatistics and Medical Informatics, and *Medicine (Division of Endocrinology); University College of Medical Sciences and Guru Teg Bahadur Hospital, Dilshad Garden, Delhi, India. Correspondence to: Dr Piyush Gupta, Professor of Pediatrics, University College of Medical Sciences and GTB Hospital, Dilshad Garden, Delhi 110 095, India. prof.piyush.gupta@gmail.com.
authors.forename: Pinky
authors.initials: P
authors.lastname: Meena
authors.forename: Aashima
authors.initials: A
authors.lastname: Dabas
authors.forename: Dheeraj
authors.initials: D
authors.lastname: Shah
authors.forename: Rajeev Kumar
authors.initials: RK
authors.lastname: Malhotra
authors.forename: S V
authors.initials: SV
authors.lastname: Madhu
authors.forename: Piyush
authors.initials: P
authors.lastname: Gupta
mesh_terms: D001942:Breast Feeding; D006801:Humans; D007223:Infant; D010789:Phototherapy; D011446:Prospective Studies; D013472:Sunlight; D014807:Vitamin D / Q000097:blood*; D014808:Vitamin D Deficiency / Q000517:prevention & control / Q000628:therapy
chemical_list: D014807:Vitamin D