title: Circadian Macronutrients Variations over the First 7 Weeks of Human Milk Feeding of Preterm Infants.
abstract: BACKGROUND
  Little is known about circadian variations of macronutrients content of expressed preterm human milk (HM). This study evaluated diurnal variations of macronutrients and energy content of preterm HM over the first 7 weeks of lactation and tested the hypothesis that values obtained during a morning sample are predictive of those obtained from an evening sample.
  
  
  METHODS
  Expressed HM was obtained from 32 mothers of preterm infants (26-33 weeks in gestational age), who routinely expressed all their milk every 3 hours from the beginning of the second to the seventh week after delivery. One aliquot was obtained from the first morning expression and the second from the evening expression. Energy and macronutrients contents were measured using an HM analyzer.
  
  
  RESULTS
  Mean fat and energy contents of all samples obtained during the whole period were significantly higher in evening samples (p < 0.0001). There were no significant differences between morning and evening carbohydrates and protein contents. Concentrations of protein, carbohydrates, and fat from morning samples were predictive of evening concentrations to different extents (R(2) = 0.720, R(2) = 0.663, and R(2) = 0.20, respectively; p < 0.02). The predictability of evening values by morning values was not influenced by the week of lactation at sampling or by individual patients. In repeated-measures analysis of variance performed on 11 patients who completed the whole 7-week period, over time, there was a significant decrease in fat, energy, and protein contents, whereas carbohydrates content remained unchanged. Day-night differences remained significant only for fat content.
  
  
  CONCLUSIONS
  Circadian variations in fat and energy concentrations of HM are consistent over the first 7 weeks of lactation. There are no consistent circadian variations in HM protein and carbohydrates. Over a given day, there are little variations in protein and carbohydrates content, but fat concentrations are more variable, and evening values are less well predicted by morning sample analysis than values for protein or carbohydrates.
authors.affiliation: 1 Department of Neonatology, Tel Aviv Sourasky Medical Center , Tel Aviv, Israel .|2 Department of Pediatrics, Tel Aviv Sourasky Medical Center , Tel Aviv, Israel .
authors.forename: Hadar
authors.initials: H
authors.lastname: Moran-Lev
authors.affiliation: 3 The Sackler Faculty of Medicine, Tel Aviv University , Tel Aviv, Israel .|4 Department of Neonatology, Shaare Zedek Medical Center , Jerusalem, Israel .
authors.forename: Francis B
authors.initials: FB
authors.lastname: Mimouni
authors.affiliation: 1 Department of Neonatology, Tel Aviv Sourasky Medical Center , Tel Aviv, Israel .|3 The Sackler Faculty of Medicine, Tel Aviv University , Tel Aviv, Israel .
authors.forename: Amit
authors.initials: A
authors.lastname: Ovental
authors.affiliation: 1 Department of Neonatology, Tel Aviv Sourasky Medical Center , Tel Aviv, Israel .
authors.forename: Laurence
authors.initials: L
authors.lastname: Mangel
authors.affiliation: 1 Department of Neonatology, Tel Aviv Sourasky Medical Center , Tel Aviv, Israel .|3 The Sackler Faculty of Medicine, Tel Aviv University , Tel Aviv, Israel .
authors.forename: Dror
authors.initials: D
authors.lastname: Mandel
authors.affiliation: 2 Department of Pediatrics, Tel Aviv Sourasky Medical Center , Tel Aviv, Israel .|3 The Sackler Faculty of Medicine, Tel Aviv University , Tel Aviv, Israel .
authors.forename: Ronit
authors.initials: R
authors.lastname: Lubetzky
mesh_terms: D000704:Analysis of Variance; D001942:Breast Feeding; D002940:Circadian Rhythm / Q000502:physiology*; D002149:Energy Intake; D005260:Female; D006801:Humans; D007227:Infant Nutritional Physiological Phenomena; D007231:Infant, Newborn; D007234:Infant, Premature; D007774:Lactation; D008297:Male; D008894:Milk Proteins / Q000378:metabolism*; D008895:Milk, Human / Q000737:chemistry*; D008903:Minerals / Q000378:metabolism
chemical_list: D008894:Milk Proteins; D008903:Minerals