Nutriology of Bifidobacteria

In those days before 1950, when the manufacture of powdered milk was in its early stages, it was widely recognized that breastfeeding was superior to bottle-feeding for new-born babies, because of a lower frequency of sickness (especially gastro-enteritis), better condition of the patient, and furthermore a lower mortality. There have been reported many hypotheses to explain this observation (Table 1) : Breast milk contains anti-bacterial and anti-viral proteins (secretary IgA), macrophages, lymphoid cells and iron-snatching protein (lactoferrin) ; has no alien substances as antigens; provides mental comfort to babies through close physical contact, and so on. Above all, the difference in intestinal microflora has been considered to be a big factor. In the intestines of breast-fed babies bifidobacteria grow well enough to be predominant over other bacteria (bifidus-flora). On the other hand, in the intestines of bottle-fed babies the number of bifidobacteria decreased and other bacteria such as Escherichia coli dominated in turn (Fig. 1) . Therefore the role of bifidobacteria has been of interest to many investigators such as pediatrists, dieticians, chemists and bacteriologists. These hypotheses are reviewed in references (16, 27, 35 and 53) . The investigators have found the biological activities and roles of bifidobacteria as follows (Table 2) : 1. Bifidobacteria produce acetic acid and lactic acid from sugars. These acids lower pH of a medium and have anti-bacterial effect in acidic condition (2, 8), as shown in Fig. 2. The produced acids also inhibit absorption of ammonia and amines through