title: Investigation of short-term variations in term breast milk composition during repeated breast expression sessions.
abstract: BACKGROUND
  Breast milk composition can be affected by several factors, and it can exhibit short-term (weekly) variations. Investigating variations in breast milk composition is important to accurately estimate nutrient requirements of the infant.
  
  
  OBJECTIVE
  To investigate short-term changes in breast milk composition between left and right breasts, over a 3-week period within the first 6 months of lactation.
  
  
  METHODS
  The left and right breasts of the mothers of healthy, term infants (n = 23) were simultaneously expressed with an electric breast pump for 15 minutes, on 3 occasions within 3 weeks. Milk samples (5 mL) were collected from the total expression volume of each breast at each session. The macronutrient contents, total solids, and energy content were determined using a mid-infrared human milk analyzer. Mothers (n = 17) measured their 24-hour milk production, and the average 24-hour fat contents were also determined.
  
  
  RESULTS
  Over the 3 weekly sessions, no significant changes were found in macronutrient contents. On average, total solids (P = .04) and energy (P = .04) decreased by week 3 of follow-up sessions from 14 to 13 g/100 mL and from 82 to 76 Kcal/100 mL, respectively; however, these changes became insignificant when expression volume was taken into account. The macronutrient concentration was similar for the left and right breasts; however, milk composition varied markedly between mothers. Furthermore, average 24-hour fat content was significantly lower than the mean fat content from a single expression session (P < .01).
  
  
  CONCLUSIONS
  Our findings highlight that when determining the nutritional adequacy of a mother's milk, assuming an average concentration requires caution. The study findings illustrate the importance of using average 24-hour fat content of milk to obtain representative measures of infant energy intake.
authors: School of Chemistry and Biochemistry, The University of Western Australia, Crawley, Western Australia, Australia.
authors: Sadaf
authors: S
authors: Khan
authors: Danielle K
authors: DK
authors: Prime
authors: Anna R
authors: AR
authors: Hepworth
authors: Ching Tat
authors: CT
authors: Lai
authors: Naomi J
authors: NJ
authors: Trengove
authors: Peter E
authors: PE
authors: Hartmann
mesh_terms: D000328:Adult; D061186:Breast Milk Expression; D002149:Energy Intake; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008895:Milk, Human / Q000737:chemistry*; D009751:Nutritional Requirements