In contrast to other prebiotics, lactulose has up to now been mainly used as a medicinal drug for constipation and hepatic encephalopathy(6). In 1957 Petuely published the basic work about lactulose as "the bifidus factor" which was confirmed by MacGillivray et al(6).They found that the composition of the colonic microflora of bottle-fed babies is very much like that of adults while if lactulose is added to the formula milk such babies have the same composition as breast-fed babies.