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Sunlight Exposure and Vitamin D Status in Breastfed Infants
Pinky Meena1, Aashima Dabas, Dheeraj Shah
1Departments 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.
Insights
Sunlight exposure, particularly in the afternoon, significantly correlates with vitamin D levels in infants. Achieving sufficient vitamin D requires approximately 30 minutes of weekly afternoon sun exposure for infants.
Area of Science:
- Pediatrics
- Nutritional Science
- Public Health
Background:
- Vitamin D deficiency is a prevalent issue in infants, particularly those who are predominantly breastfed.
- Maternal vitamin D status is a key factor, but infant sunlight exposure also plays a crucial role.
Purpose of the Study:
- To determine the relationship between sunlight exposure in the first six months of life and vitamin D status at six months in predominantly breastfed infants.
- To quantify the necessary sunlight exposure to achieve adequate serum 25(OH)D levels (>20 ng/mL) by six months of age.
Main Methods:
- A prospective cohort study was conducted with 132 healthy, term-born, predominantly breastfed infants in Delhi.
- Maternal vitamin D levels were measured at enrollment, and mothers recorded infant sunlight exposure details (duration, timing, body surface area) for six months.
- Infant serum 25(OH)D levels were measured at six months, with a Cumulative Sun Index calculated and correlated with vitamin D status, adjusting for covariates.
Main Results:
- A significant positive correlation (r=0.461, P<0.001) was found between the Cumulative Sun Index and infant serum 25(OH)D levels at six months.
- Afternoon sun exposure showed a significant positive impact, with a 1-unit increase in afternoon sun index raising serum 25(OH)D by 1.07 ng/mL (P=0.003).
- An estimated 30 minutes of weekly afternoon sunlight exposure (10 am-3 pm) over 40% of body surface area for at least 16 weeks was required for sufficient vitamin D levels (>20 ng/mL).
Conclusions:
- Afternoon sunlight exposure is independently associated with improved vitamin D levels in infants.
- This finding suggests that sunlight exposure is a viable intervention for preventing and treating vitamin D deficiency in infants.
- Further randomized controlled trials are recommended to confirm the efficacy of sunlight exposure as an intervention.
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:
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 Measures:
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.
Conclusion:
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.
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