Previous studies suggest that probiotic-enhanced diets improve mineral absorption in the large intestine and are thus protective against bone mineral loss. A synbiotic diet, composed of both probiotics and prebiotics, may be even more effective because the bacteria can readily metabolize the fibers of the prebiotics to promote growth and synthesis of secondary metabolites. Here, we investigated if aging-related changes in bone mineralization and mechanical strength are influenced by a synbiotic diet. Specifically, we hypothesized that a synbiotic diet would enhance bone mineralization and improve humerus bone strength in aging mice. Dual energy X-ray absorptiometry revealed that the diet did not enhance mineralization of humerus bones in male retired breeder mice. It did, however, reveal that the diet influenced the size (area) of the bones. Mechanical strength testing showed that the diet did not enhance the strength of the humerus bones.