title: Determinants of 25-Hydroxyvitamin D Concentrations in Infants and Toddlers.
abstract: BACKGROUND
  Resurgence of rickets and recognition of excessive prevalence of hypovitaminosis D among all age groups in the western hemisphere have refocused attention on vitamin D nutrition.
  
  
  OBJECTIVE
  To examine the prevalence of hypovitaminosis D [25-hydroxyvitamin D [25(OH)D] <30ng/mL] and characterize the determinants of 25(OH)D concentrations in 8- to 24-month-old healthy infants and toddlers living in Pittsburgh, Pennsylvania.
  
  
  METHODS
  Serum 25(OH)D concentrations were measured and dietary intake of vitamin D, mode of feeding, summertime sun exposure characteristics, and skin color (sun-reactive skin type and melanin index) were assessed.
  
  
  RESULTS
  A total of 111 healthy 8- to 24-month-old children (mean age [±SD] 14.4 [±3.5] months; male, 51%; black, 67%) were studied. Serum 25(OH)D concentration was <30 ng/mL in 16% (n=18) of the children. Median (interquartile) 25(OH)D concentration was lower in children who were ≥ 13 months vs. <13 months of age [35 (31, 40.5) vs. 40 (35.8, 44.3) ng/mL, p=0.013]; with sun-reactive skin type IV and V vs. I, II, and III [36 (31, 41) vs. 44 (36.5, 48.5) ng/mL, p=0.001]; and examined during fall/winter vs. spring/summer [35.5 (32.5, 38.5) vs. 39 (32.5, 44) ng/mL, p=0.05]. Age and skin type were significant independent predictors of 25(OH)D.
  
  
  CONCLUSIONS
  Concentrations of 25(OH)D tend to be lower in infants and toddlers during fall/winter, and in children who are older (≥13 months vs. <13 months of age) and have darker skin tone. Benefits of enhancement of 25(OH)D concentrations during fall/winter and in children with higher sun-reactive skin type need further exploration.
authors.affiliation: Department of Pediatrics, University of Pittsburgh, Pittsburgh, PA, United States.
authors.forename: Hilary
authors.initials: H
authors.lastname: Michel
authors.affiliation: Department of Pediatrics, University of Pittsburgh, Pittsburgh, PA, United States.
authors.forename: Flora
authors.initials: F
authors.lastname: Olabopo
authors.affiliation: Clinical and Translational Science Institute, University of Pittsburgh, Pittsburgh, PA, United States.
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Nutrition, Georgia State University, Atlanta, GA, United States.
authors.forename: Anita
authors.initials: A
authors.lastname: Nucci
authors.affiliation: Department of Medicine, University of Pittsburgh, Pittsburgh, PA, United States.
authors.forename: Susan L
authors.initials: SL
authors.lastname: Greenspan
authors.affiliation: Department of Pediatrics, University of Pittsburgh, Pittsburgh, PA, United States.
authors.forename: Kumaravel
authors.initials: K
authors.lastname: Rajakumar
keywords: infants; skin pigmentation; sun exposure toddlers; vitamin D