Special Issue Article
Pinky Meena, MGM Medical
Abstract
Objective: To correlate sunlight exposure to vitamin D status in predominantly breastfed infants; and to quantify sunlight exposure required to achieve serum 25(OH)D level >20 ng/mL, by 6 months of age. Methods: 132 healthy term, predominantly breastfed infants were enrolled at 6-8 weeks of age. Of these, 100 infants were available for final evaluation. Maternal serum 25(OH)D levels were obtained at enrolment. Mothers were counselled regarding a daily record of duration of sunlight exposure, timing of exposure, and body surface area exposed, for the infant, on a pre-designed performa. Infant’s serum 25(OH)D was measured at 6 months of age. Cumulative Sun Index (CSI) was calculated and correlated with the infant serum 25(OH)D after adjusting for confounding factors. Sun index for exposure before 10am and between10am and 3pm were correlated to 25(OH)D. Results: Ninety mothers had serum 25(OH)D <12 ng/mL. Median duration of sunlight exposure of infants was 17 min/week, on 6% of body surface area. CSI correlated positively to infants’ serum 25(OH)D levels at 6 months (r= 0.461, P<0.001). Increment in afternoon sun index by 1unit increased serum 25(OH)D levels by 1.07 ng/mL (95% CI 0.37-1.78; P= 0.003). Weekly 30 minute 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 25(OH)D levels >20 ng/mL by 6 months of age.