Variation in fat, lactose and protein in human milk over 24 h and throughout the first year of lactation.
Fat in human milk is extremely variable and can represent up to 50 % of infant energy intake. To accurately determine milk composition and infant intake at 1 (n 17), 2 (n 17), 4 (n 17), 6 (n 15), 9 (n 6) and 12 (n 5) months of lactation, samples of fore- and hind-milk were collected from each breast at each feed over 24 h periods from an initial group of seventeen women. The content of fat in milk varied over 24 h, with a mean CV of 47.6 (se 2.1) % (n 76) and 46.7 (se 1.7) % (n 76) for left and right breasts respectively. The 24 h amounts of fat, lactose and protein in milk differed between women (P=0.0001), but were consistent between left and right breasts. Daily milk production differed between breasts (P=0.0001) and women (P=0.0001). Accordingly, amounts of fat (P=0.0008), lactose (P=0.0385) and protein (P=0.0173) delivered to the infant over 24 h also differed between breasts and women (P=0.0001). The energy content of milk and the amount of energy delivered to the infant over 24 h were the same between breasts, but differed between women (P=0.0001). The growth rate of a group of only six infants in the present study was not related to either the concentrations or amounts of fat, lactose, protein and energy in milk over the first 6 months of life. These results show the individuality of milk composition and suggest that only a rigorous sampling routine that takes into account all levels of variation will allow the accurate determination of infant intake of fat, lactose, protein and energy.
Mitoulas
Leon R
LR
Department of Biochemistry, The University of Western Australia, 35 Stirling Highway, Crawley, Australia. Leon.Mitoulas@uwa.edu.au
Kent
Jacqueline C
JC
Cox
David B
DB
Owens
Robyn A
RA
Sherriff
Jillian L
JL
Hartmann
Peter E
PE
D000293:Adolescent; D000328:Adult; D002657:Child Development / Q000502:physiology; D005260:Female; D005500:Follow-Up Studies; D006128:Growth / Q000502:physiology; D006801:Humans; D007223:Infant; D007227:Infant Nutritional Physiological Phenomena / Q000502:physiology; D007231:Infant, Newborn; D007774:Lactation / Q000502:physiology*; D007785:Lactose / Q000032:analysis / Q000378:metabolism*; D050356:Lipid Metabolism; D008055:Lipids / Q000032:analysis; D008894:Milk Proteins / Q000032:analysis / Q000378:metabolism*; D008895:Milk, Human / Q000737:chemistry / Q000378:metabolism*
D008055:Lipids; D008894:Milk Proteins; D007785:Lactose