Evidence in the nutritional literature suggests that breastfeeding holds a number of advantages over the use of formula milk. In particular the fatty acid content of human milk is high in docosahexaenoic acid (DHA, C22:6 (n-3)) and this may optimally aid the development of the brain of the infant as it develops. Studies comparing breastfed infants with formula fed infants show that the former are protected from certain Western lifestyle diseases, particularly cardiovascular disease and obesity. One of the reasons for the protective effect of breastfeeding may relate to the ability of human milk to stimulate the colonisation of the colon with a favourable microfloral profile that is conductive to health and optimal development of the immune system. Analysis of breastfed infants for example shows that they possess a predominance of Bifidobacterium. Infants fed with milk from cows also possess Bifidobacterium, but species differences in comparison to breast fed infants may exist.
The reason for the difference in the profiles of the Bifidobacterium between breastfed and formula fed infants may relate to specific prebiotic growth factors in the milk of humans. For example, one study has measured the ability of human milk or cow’s milk to stimulate the growth of a range of Bifidobacterium species using in vitro studies1. The results of the study showed that only Bifidobacterium bifidum was stimulated to growth by the human milk, and this they suggested was due to specific growth factors that the authors designated factor ‘BB’. Subsequent work since this paper has confirmed the presence of Bifidogenic factors in human milk that are designated bifidus factors (BF) and a number have been described. In addition a number of glycoproteins may also be present that have prebiotic effects. In subsequent experiments it has been shown that colostrum from human milk possesses the prebiotic effects, but that these effects are destroyed by sterilisation, pasteurisation or freeze-drying.
Analysis of fresh unpasteurised cow’s milk shows that it too may possess prebiotic growth factors that are able to cause the growth of Bifidobacterium species in vitro. However, while human milk stimulates the growth of Bifidobacterium bifidum, cow’s milk stimulates the growth of bifidobacterium longum and Bifidobacterium infantis. Analysis of milk from other mammals including sheep, pig and horse shows them to possess similar growth promoting prebiotic activity to cow’s milk, and are therefore distinct from human milk in this respect. Because these factors are active in vitro, they do not require activation by gastrointestinal enzymes. Therefore mammalian milk contains a number of different growth factors that are species specific and these have prebiotic effects in the infant mammals. Differences in the prebiotic effects of milk likely reflects the differing needs of the animals based on contrasting physiologies. This provides more evidence of the superiority of human milk over formula milk in human nutrition.
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