Infants need more sun than 17 minutes per week on 6 percent of skin – Dec 2016

Sunlight Exposure and Vitamin D Status in Breastfed Infants.

Indian Pediatr. 2016 Dec 5. pii: S097475591600032. [Epub ahead of print]
Meena P1, Dabas A, Shah D, Malhotra RK, Madhu SV, Gupta P.

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.
DESIGN:
Prospective cohort.
SETTING:
Tertiary care hospital predominantly catering to urban poor population in Delhi.
PARTICIPANTS:
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.
MAIN OUTCOME MEASURE:
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 (10am-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% 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 levels 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 levels 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.

PMID: 28031546

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VitaminDWiki disagrees with their conclusion

White-skinned child needs to build up to getting > 90 minutes weekly sun during the summer with diapers to get to 30 nanograms
Even longer time in the sun for dark-skinned children

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