title: [Foremilk and hindmilk retinol levels].
abstract: OBJECTIVE
  To determine retinol levels in breast milk at the beginning and at the end of a feeding.
  
  
  METHODS
  In 2003, 30 breastfeeding women receiving care at the Januário Cicco Maternity School, in the city of Natal, Rio Grande do Norte, Brazil, were interviewed between 24 hours and 15 days after delivery. A four mL sample of breast milk was expressed manually (2 mL at the beginning and 2 mL at the end of the feeding) in the afternoon, two hours after the preceding feeding. Retinol levels were determined by high performance liquid chromatography. Student's t test was used for statistical analysis.
  
  
  RESULTS
  The mean retinol concentrations in the breast milk samples collected at the beginning and at the end of the same feeding were 69.3 +/- 41.4 microg/100 mL and 111.6 +/- 79.2 microg/100 mL, respectively; the mean concentrations were statistically different (P = 0.012).
  
  
  CONCLUSIONS
  Our results suggest that hindmilk provides a higher intake of vitamin A. Therefore, it is important to guide mothers to not limit the baby's time at the breast and to avoid expressing only foremilk. In addition, it is important to standardize the time of breast milk collection in order to allow comparisons between the results of different studies on this topic.
authors.affiliation: Universidade Federal do Rio Grande do Norte (UFRN), Centro de Biociências, Departamento de Bioquímica, Base Bioquímica da Nutrição, Natal (RN), Brasil.
authors.forename: Karla Danielly da Silva
authors.initials: KD
authors.lastname: Ribeiro
authors.forename: Roberto
authors.initials: R
authors.lastname: Dimenstein
mesh_terms: D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007774:Lactation / Q000378:metabolism*; D008895:Milk, Human / Q000737:chemistry*; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires; D014801:Vitamin A / Q000032:analysis*
chemical_list: D014801:Vitamin A