Dietary xylitol supplementation increases the calcium and phosphorus levels of bones in rats, and it protects against decreases in bone minerals and bone density during experimental osteoporosis. Xylitol reduces the rate of bone resorption and protects against increases in bone resorption during experimental osteoporosis. Xylitol intake also leads to increased trabecular bone volume in the long bones of healthy rats and protects against decreases in trabecular bone volume during experimental osteoporosis. Dietary xylitol supplementation also increases the strength properties of long bones in healthy rats and protects against weakening of bone biomechanical properties during experimental osteoporosis. A continuous moderate dietary xylitol supplementation protects significantly against osteoporotic changes in aged rats. Moreover, xylitol protects against streptozotocin-induced osseal changes during experimental type I diabetes. Furthermore, in the skin of diabetic rats, dietary xylitol protects against the decrease in the amount of newly synthesized collagen, against the increase in the hexose content of acid-soluble collagen, and against the increase in fluorescence of the collagenase-soluble fraction. In conclusion, the above results strongly support the hypothesis that oral administration of xylitol protects effectively against progression of experimental osteoporosis following ovariectomy and during aging. Furthermore, dietary xylitol protects against undesirable changes in the bones and in the skin of streptozotocin-diabetic rats.