Differential Osteogenic Effect of Phytase Supplementation to a Low Zinc Diet in Rats

Abstract

Adding vitamin D to a low calcium diet is known to effect trabecular but not cortical bone. Although adding phytase (P) to a low zinc (Zn) diet improves overall bone strength by increasing the bioavailability of Zn and other micronutrients, it is unknown if this supplementation has a differential effect on cortical and trabecular bone.PurposeExamine the effect of P‐supplementation to a low Zn diet in cortical and trabecular bone in both, L‐4 vertebrae and tibiae of rats.MethodsMale Sprague‐Dawley rats were fed a diet containing either 5ppm Zn (ZnLo) (n=10), 5ppm Zn+1,500FTU/kg P (ZnLo+P) (n=10), or 30ppm Zn (ZnAd) (n=10) for 9 wks. In vivo peripheral quantitative computed tomography was used to scan right tibiae at 10% (trabecular parameters) and 50% (cortical parameters) of total. The L‐4 vertebrae were scanned at the 40, 50, and 60% of total length; an average of these represented the mid‐20% vertebral region. One way ANOVA determined group differences for cortical and trabecular bone mineral content (BMC), bone area (BA) and bone mineral density (BMD).ResultsCortical parameters at the L‐4 were significantly higher in rats fed ZnLo+P compared to ZnLo diets. There was no significant difference between groups in trabecular parameters.ConclusionIn contrast to the vitamin D:calcium relationship, P‐supplementation of a low Zn diet exhibited a positive effect on cortical BMD, BMC and BA at the L‐4 site, but had no effect on trabecular or tibial parameters.The study was funded by the U.S.Army MRMC