Feeding Human Milk to Rats Increases Bifidobacterium in the Cecum and Colon Which Correlates with Enhanced Folate Status

The purpose of this investigation was to determine if feeding diets containing human milk resulted in increased numbers of microorganisms implicated in increased folate production and the effect on folate availability. Following a folate-depletion period (5 wk), 30 rats were fed folate-repletion diets (4 wk) with or without 20% milk solids (human, cow or goat) and containing either 906 or 4530 nmol folic acid/kg. At the end of the test period, the cecum and colon were removed in an anaerobic chamber, homogenized, diluted (10(-2) -10(-8)), and the contents of each plated on selective and nonselective media. In addition to enumeration of the total anaerobic load, five genera of bacteria were counted (Bacteroides, Bifidobacterium, Clostridium, Escherichia and Streptococcus). Rats fed human milk solids had at least a seven- and onefold mean increase in the Bifidobacterium concentration in the cecum (P < 0.006) and colon (P < 0.04), respectively, compared with rats fed other diets. The total anaerobic bacterial concentration in the cecum and the colon of rats fed human milk solids was also greater than that of rats fed the other diets (P < 0.05). The single exception was the total anaerobic count in the cecum of rats consuming goat milk solids, which did not differ from that of rats consuming human milk solids. Further, rats fed human milk solids had at least a 42 and 48% higher mean plasma folate concentration and total cecal material folate content, respectively, than rats in other dietary treatments containing 906 nmol/kg folic acid. Therefore, the improved folate status of rats fed human milk-containing diets appears to be due, at least in part, to increased folate synthesis by Bifidobacteria and other folate-synthesizing microbes in the cecum and colon.