Abstract
Previously we reported low serum 25-hydroxyvitamin D (25OHD) in breast fed infants without vitamin D supplements. However prospective serum 25-OHD vs sun exposure studies have not been done in relation to season of birth. We hypothesized that breast-fed infants <1 yr of age have serum 25-OHD varying directly with sun exposure & that opposite patterns occur in summer vs winter-born infants. 25 term infants exclusively breast-fed without vitamins were followed longitudinally from birth for > 6 mos: 13 born in summer and 12 winter. Sun exposure was monitored for 1 wk of every mo until 12 mos. A sun exposure score, previously verified, quantified time & surface area exposed (e.g., 0=no exposure, 5=13hrs/wk, diaper only). 25-OHD was determined by protein-binding assay (N 11-68ng/ml; CV 11%). Mean (±sem) values by age were:
Monthly exposure scores peaked in summer, were low in winter (p< .01), & intermediate in fall & spring. 25-OHD paralleled sun exposure, irrespective of age; 25-OHD was correlated with exposure (r=.54, p<.001). Thus, summer vs winter-born infants had mirror image patterns of both sun exposure and 25-OHD; large seasonal differences in both sun exposure and 25-OHD were observed.
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Specker, B., Buckley, D., Searcy, J. et al. 1264 CYCLICAL SERUM 25-HYDROXYVITAMIN D PARALLELLING SUNSHINE EXPOSURE IN EXCLUSIVELY BREAST-FED INFANTS: MIRROR IMAGE IN SUMMER VS WINTER BORN. Pediatr Res 19, 321 (1985). https://doi.org/10.1203/00006450-198504000-01294
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DOI: https://doi.org/10.1203/00006450-198504000-01294