title: Vitamin D status of exclusively breastfed 4-month-old infants supplemented during different seasons.
abstract: OBJECTIVE
  To examine the vitamin D status of 4-month-old exclusively breastfed infants supplemented with 400 IU daily of vitamin D and to determine whether there was any seasonal variation in serum 25-hydroxyvitamin D (25(OH)D) levels of infants.
  
  
  METHODS
  In this cross-sectional study, serum calcium, phosphorus, alkaline phosphatase, parathyroid hormone, and 25(OH)D levels of 143 exclusively breastfed 4-month-old infants supplemented daily with 400 IU of vitamin D were measured in a temperate latitude, Izmir, Turkey, between May 2008 and April 2009. A questionnaire on demographic characteristics of infants and mothers, vitamin D supplementation of infants after birth, mothers' multivitamin supplementation, dressing habits, and consumption of dairy products during pregnancy was used.
  
  
  RESULTS
  Vitamin D deficiency (≤ 50 nmol/L) and insufficiency (51-74 nmol/L) were determined in 40 (28%) and 55 (38.5%) infants, respectively. During winter days, serum 25(OH)D levels were <20 ng/mL in 45.4% of infants and <10 ng/mL in 10.6% of infants. Season of blood sampling, compliance of vitamin D supplementation, maternal education level, and consumption of dairy products were highly predictive of serum 25(OH)D levels in multiple linear regression analysis (P < .05). The use of the Pearson correlation test found a statistically significant negative correlation between 25(OH)D and parathyroid hormone levels (r = -0.419, P < .001).
  
  
  CONCLUSIONS
  Despite supplementation with 400 IU of vitamin D daily, the rate of vitamin D deficiency was worryingly high in 4-month-old exclusively breastfed infants living in Izmir, Turkey. So, additional studies are needed to clarify optimal amount of vitamin D supplementation to the infants, especially during winter days.
authors.affiliation: Department of Pediatrics, The Ministry of Health Tepecik Teaching and Research Hospital, 119/1 sk. No: 5 Basinkent site B blok/6, 35050 Bornova- Izmir, Turkey. oyahalicioglu@yahoo.com.tr
authors.forename: Oya
authors.initials: O
authors.lastname: Halicioglu
authors.forename: Sumer
authors.initials: S
authors.lastname: Sutcuoglu
authors.forename: Feyza
authors.initials: F
authors.lastname: Koc
authors.forename: Omur
authors.initials: O
authors.lastname: Yildiz
authors.forename: Sezin A
authors.initials: SA
authors.lastname: Akman
authors.forename: Sadik
authors.initials: S
authors.lastname: Aksit
mesh_terms: D015415:Biomarkers / Q000097:blood; D001942:Breast Feeding; D002762:Cholecalciferol / Q000627:therapeutic use*; D003430:Cross-Sectional Studies; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D007223:Infant; D016014:Linear Models; D008297:Male; D012307:Risk Factors; D012621:Seasons; D011795:Surveys and Questionnaires; D016896:Treatment Outcome; D014421:Turkey; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000175:diagnosis / Q000209:etiology / Q000517:prevention & control*; D014815:Vitamins / Q000627:therapeutic use*
chemical_list: D015415:Biomarkers; D014815:Vitamins; D014807:Vitamin D; D002762:Cholecalciferol; C104450:25-hydroxyvitamin D