In the present study an ovariectomized osteoporosis model rat was used to investigate the effect of Bifidobacterium and undigestible lactulose on whey calcium absorption and bone fracture properties. Ovariectomized rats received a diet containing 0.01% Ca for 31 days. Thereafter, the rats were divided into three groups fed the following 3 diets for 31 days: a diet containing whey calcium (group 1), a diet containing whey calcium and Bifidobacterium culture suspended in drinking water (group 2), and a diet containing whey calcium and lactulose, and Bifidobacterium culture suspended in drinking water (group 3).The experiment yielded the following results. The number of bifidobacteria in the feces was significantly increased by administration of lactulose. The pH of the cecal contents was reduced concomitantly with increasing numbers of bifidobacteria in the feces, and the concentration of acetic acid in the cecal contents was significantly higher in group 3. The femur fracture properties (breaking energy and breaking force) in groups 2 and 3 were increased in comparison with animals fed only the whey calcium diet (group 1).There was no significant difference in the values of the microdensitometry parameters ΣGS and GS_max among the 3 groups, but ΣGS/D was higher following administration of Bifidobacterium and lactulose as compared to group 1. This was a significant difference. GS_min in group 2 was statistically higher than that in group 1. These results suggest that administration of Bifidobacterium and lactulose promotes whey calcium absorption, and thereby increases the strength of bone.

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