Variation in fat, lactose and protein in human milk over 24h and throughout the first year of lactation
2002
Mitoulas, L.R. | Kent, J.C. | Cox, D.B. | Owens, R.A. | Sherriff, J.L. | Hartmann, P.E.
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=0.001) and women (P=0.001). 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.
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