 The XOS was tolerated well by all study subjects normal adult. At base-line, most of the subjects had relatively high counts of Bifidobacterium species with lower counts of Lactobacillus species. Several different species of each of these genera were present. Bifidobacterium species showed significant increases in counts in subjects on XOS supplementation, with the higher dose group showing significantly greater increases than the lower dose group. Both high and low dose groups showed significantly higher counts of Bifidobacterium sub-species than the placebo group. Lactobacillus species counts did not increase significantly in subjects on XOS supplementation. There was a statistically significant increase in the counts of the B. fragilis group at all time periods for the high dose XOS group. As mentioned before, bifidobacteria may induce host genes involved in innate immunity in collaboration with other elements of the gut flora such as B. fragilis group. The increase in the counts of the total anaerobes reflects the increased counts in the Bifidobacterium and B. fragilis group, both of which are anaerobic. Some Bifidobacterium species may grow aerobically as well, which may be reflected in the modest increase of the aerobic counts in the high dose XOS group. In this study, the XOS supplementation had no significant effect on stool pH or SCFAs. 