Human milk composition

As it can be seen in Table 13.2, human milk composition is quite different from that of cow s milk. Casein and mineral contents are lower in human milk than in cow s milk, whilst the lactose content is higher in the former. With regards to fatty matter, both types of milk present similar contents, but the total protein is over three-fold higher in cow s milk. 

Infant formula Nutrition, solubility, emulsification, colloidal stability to heat Mimic human milk composition... 

Although human milk composition can be a guide to that of breast milk substitutes, the comparison of outcomes with those seen in healthy infants who have been exclusively breast fed for 4-6 months is considered a better approach. 

CHALLENGES OF MATCHING HUMAN-MILK COMPOSITION AND BREASTFEEDING PERFORMANCE... 

Infant formula manufacturers have made changes to formulas in order to match either human milk composition or breastfeeding performance (Benson and Masor, 1994). The term breastfeeding performance is used because, with the exception of one study of preterm infants (Lucas et al., 1994), all other studies comparing human milk with formulas involved breastfeeding— not providing human milk from a bottle. 

Historically one approach to match human-milk composition is to add new ingredients (see Appendix B for the composition of formulas and human milk). This turns out to be a quixotic quest since human milk is a complex body fluid that is variable not only among individuals, but within an individual over time. In addition, it contains components, such as live cells and bioactive compounds, that either cannot be added to formulas or cannot survive a shelf life. Finally, not all human-milk constituents are essential some, like LC-PUFAs, docosahexaenoic acid (DHA), and arachidonic acid (ARA), can be synthesized by term and preterm infants born at 33 weeks gestation (Uauy et al., 2000). 

From a research standpoint, clinical studies that assess the effects of new ingredients will be difficult to design because infants cannot be randomized to be formula fed or breastfed. Furthermore, there may be significant non-nutritional confounding variables between the groups, including, but not limited to, factors related to which mothers breastfeed. Finally, human-milk composition varies considerably among individuals and within individuals over time, while infant formula content remains constant. 

The identification of PCB residues in fish, wildlife, and human tissues has been reported since the 1970s (9—13,20—26). The results of these analytical studies led to the ultimate ban on further use and production of these compounds. The precise composition of PCB extracts from biota samples is highly variable and depends, in part, on the specific analyte and the commercial PCB preparations associated with a contaminated area (14). PCBs found in a composite human milk sample from Michigan (26) were highly complex, and the congener composition and their relative concentrations did not resemble any of the commercial PCB preparations. This fact raises obvious problems with regard to the ha2ard assessment of PCB mixtures (27). 

In a study completed during the early development of f.a.b.-m.s., both f.d. and f.a.b. were used to characterize 101 fractions containing neutral oligosaccharides isolated from human milk. Samples were examined as their peracetylated alditols. In subsequent work, the structures of two minor acidic oligosaccharides from human milk were investigated. The per-methylated derivatives were analyzed by f.a.b.-m.s., and their compositions and sequences were defined by the f.a.b. data. Methylation analysis and partial formolysis were the other principal methods used. 

Olfactorily active compounds carried in human milk have rarely been subjected to chemical analysis (Stafford, Horning and Zlatkis 1976 Pellizari, Hartwell, Harris III, Waddell, Whitaker and Erickson 1982 Shimoda, Ishikawa, Hayakawa and Osajima 2000 Bingham, Sreven-Tuttle, Lavin and Acree 2003), and so far no attempt was undertaken to characterize the volatile composition of human AG secretions. Thus, the degree of their chemical overlap or specificity cannot be evaluated. Here we present preliminary data from such comparative analyses of colostrum and AG secretions from the same women. 

But we must appreciate how the phosphate group acts much like the anion from a weak acid (see Chapter 6), so its exact composition will depend on the pH of solution. The pH of cow s or human milk is about 7 (see Table 6.4). If the pH decreases much below about 6 (e.g. by adding an acid in the form of orange juice), the phosphates become protonated. The emulsifying properties of casein cease as soon as its structure changes, causing the milk to separate. 

Brand-Miller, J., Bull, S., Miller, J., and McVeagh, P. (1994). The oligosaccharide composition of human milk Temporal and individual variations in monosaccharide components. J. Pediatr. Gastroenterol. Nutr. 19, 371-376. 

The role of milk in nature is to nourish and to provide immunological protection to the mammalian young. The nutritional value of milk is high. It comes from various sources, such as human, goat, buffalo, sheep, and yak, and has been a food for humans since prehistoric times. It is also a very complex food with many thousands of different molecular species found in it. There are several factors that can affect milk composition. An approximate composition of milk can be given as follows ... 

Darragh, A. J., and Moughan, P. J. (1998). The amino acid composition of human milk corrected for amino acid digestibility. Br. J. Nutr. 80,25-34. 

Williamson, M. T., and Murti, P. K. (1996). Effects of storage, time, temperature, and composition of containers on biologic components of human milk. /. Hum. Lact. 12,31-35. Wilson, A. C., Eorsyth, J. S., Greene, S. A., Irvine, L., Hau, C., and Howie, P. W. (1998). Relation of infant diet to childhood health Seven year follow up of cohort of children in Dundee infant feeding study. BMJ 316, 21-25. 

The pH optima of human milk lysozyme (HML), bovine milk lysozyme (BML) and egg-white lysozyme (EWL) are 7.9, 6.35 and 6.2, respectively. BML has a molecular weight of 18kDa compared with 15kDa for HML and EWL. The amino acid composition of BML is reported to be considerably different from that of HML or EWL. All lysozymes are relatively stable to heat at acid pH values (3-4) but are relatively labile at pH greater than 7. Low concentrations of reducing agents increase the activity of BML and HML by about 330%. 

Jenness, R. 1979. The composition of human milk. Semin. Perinatol. 3, 225-239. 

Martel, M. B Dubois, P. and Got, R. 1973. Membranes of human milk lipid globules. Preparation, morphology and chemical composition. Biochim. Biophys. Acta 311, 565-575. (French)... 

Milk composition is not constant and is influenced by the timing of feeding and duration of nursing postpartum. Human milk contains about 2-3% fat and a large number of proteins. The pH of milk tends to be lower than that of plasma. Most water-soluble substances are excreted into the milk by simple diffusion, and lipid-soluble compounds are transported along with lipid molecules from plasma into the mammary gland. The amount of a certain substance transferred to the milk depends on the physicochemical properties of the... 

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