Effect of administration of milk fermented with Lactobacillus acidophilus LA-2 on fecal mutagenicity and microflora in the human intestine.

To demonstrate the antimutagenic effect of fermented milk in the human intestine, fecal mutagenicity and bacterial composition of six healthy subjects consuming their regular diet were investigated before and during the administration of milk fermented with Lactobacillus acidophilus LA-2. The administration of the fermented milk caused a remarkable decrease (71.9% on the average; range of 19.4 to 90.6%) in fecal mutagenicity compared with that before the administration; Lactobacillus spp. and Bifidobacterium spp. population increased in the feces of all subjects. The suppression of fecal mutagenicity appeared to be due to the change in fecal microflora caused by the presence of strain LA-2 in the human intestine.