Abstract: Objective: To study the effects of dietary fibers with different structures on calcium balance and biomechanical properties. Methods: Rats were fed a basal diet supplemented with 50 g/kg wheat bran, cellulose, xylan, pectin, inulin, konjac gum or their mixture. The contents of calcium in diets, feces, urine and femur were detected by atomic absorption spectrometry (AAS). The levels of total calcium, free calcium and bound calcium in serum were measured by an electrolyte analyzer. The maximum load of femur was measured by a three-point bending method. The effects of different dietary fibers on calcium absorption, blood calcium level, urinary calcium loss, calcium retention, bone calcium content and bone biomechanical properties were compared. Results: The calcium absorption rates in the wheat bran and cellulose supplementation groups were higher than those in the xylan, pectin, inulin and konjac supplementation groups, and the difference between the xylan and konjac supplementation groups and the wheat bran supplementation group was significant (P < 0.01). The level of urinary calcium in the xylan and cellulose supplementation groups were lower than that in the other groups. The pectin supplementation group had the lowest calcium retention rate and showed a negative calcium balance. There was no difference in serum free calcium level between the wheat bran supplementation group and the other groups (P > 0.05), but the concentrations of bound calcium and total calcium in the wheat bran supplementation group were higher than those in the other groups. The bone calcium content and bone biomechanical properties in the pectin supplementation group were significantly lower than those in the other groups, and the maximum load of femur was the highest in the xylan supplementation group. Conclusion: The intestinal calcium absorption of low fermentable dietary fibers such as wheat bran and cellulose is higher than that of high fermentable dietary fibers such as xylan, pectin, inulin and konjac. Xylan can improve the biomechanical properties of rat bones. Different dietary fibers have different effects on calcium absorption, bone calcium content and calcium balance in rats.

Key words: dietary fiber; calcium balance; maximum load of femur; biomechanical properties; calcium absorption