Military Nutrition Division, US Army Research Institute of Environmental Medicine, Natick, MA 01760, USA.
J Nutr Biochem. 2010 Jul;21(7):653-8. doi: 10.1016/j.jnutbio.2009.03.015. Epub 2009 Jul 2.
Phytic acid forms insoluble complexes with nutritionally essential minerals, including zinc (Zn). Animal studies show that addition of microbial phytase (P) to low-Zn diets improves Zn status and bone strength. The present study determined the effects of phytase supplementation on bone mineral density (BMD), body composition and voluntary running activity of male rats fed a high phytic acid, low-Zn diet. In a factorial design, rats were assigned to ZnLO (5 mg/kg diet), ZnLO+P (ZnLO diet with 1500 U phytase/kg) or ZnAD (30 mg/kg diet) groups and were divided into voluntary exercise (EX) or sedentary (SED) groups, for 9 weeks. SED rats were significantly heavier from the second week, and no catch-up growth occurred in EX rats. Feed intakes were not different between groups throughout the study. ZnLO animals had decreased food efficiency ratios compared to both phytase-supplemented (ZnLO+P) and Zn-adequate (ZnAD) animals (P<.01 compared to ZnLO). The ZnLO+P and ZnAD rats ran 56-75 km more total distance than ZnLO rats (P<.05), with the ZnLO+P rats running more kilometers per week than the ZnLO rats by Week 6. In vivo DEXA analyses indicate that rats fed phytase-supplemented diets had higher lean body mass (LBM) than those fed ZnLO diets; and that rats fed the Zn-adequate diets had the highest LBM. Body fat (%) was significantly lower in EX rats and was both Zn- and phytase insensitive. Rats fed phytase-supplemented diets had higher bone mineral content (BMC), bone area (BA) and BMD than rats fed ZnLO diets; and in rats fed ZnAD diets these indices were the highest. The dietary effects on BMC, BA and BMD were independent of activity level. We conclude that consuming supplemental dietary phytase or dietary Zn additively enhances Zn status to increase BMD, LBM and voluntary physical activity in rats fed a low-Zn diet. While the findings confirm that bone health is vulnerable to disruption by moderate Zn deficiency in rats, this new data suggests that if dietary Zn is limiting, supplemental phytase may have beneficial effects on LBM and performance activity.
植酸与包括锌（Zn）在内的多种必需营养矿物质形成不溶性复合物。动物研究表明，在低 Zn 饮食中添加微生物植酸酶（P）可以改善 Zn 状态和骨骼强度。本研究旨在确定植酸酶补充对雄性大鼠骨密度（BMD）、身体成分和自愿跑步活动的影响，这些大鼠喂食高植酸、低 Zn 饮食。在析因设计中，大鼠被分配到 ZnLO（饮食中 5mg/kg Zn）、ZnLO+P（ZnLO 饮食添加 1500U 植酸酶/kg）或 ZnAD（饮食中 30mg/kg Zn）组，并分为自愿运动（EX）或安静（SED）组，为期 9 周。SED 大鼠从第二周开始体重明显增加，而 EX 大鼠没有追赶性生长。整个研究期间，各组的饲料摄入量没有差异。与补充植酸酶（ZnLO+P）和 Zn 充足（ZnAD）动物相比，ZnLO 动物的食物效率比降低（与 ZnLO 相比，P<.01）。ZnLO+P 和 ZnAD 大鼠的总运动距离比 ZnLO 大鼠多 56-75km（P<.05），并且在第 6 周时，ZnLO+P 大鼠每周的运动距离比 ZnLO 大鼠多。体内 DEXA 分析表明，喂食植酸酶补充饮食的大鼠比喂食 ZnLO 饮食的大鼠具有更高的瘦体重（LBM）；并且喂食 Zn 充足饮食的大鼠具有最高的 LBM。EX 大鼠的体脂（%）显著降低，且对 Zn 和植酸均不敏感。喂食植酸酶补充饮食的大鼠比喂食 ZnLO 饮食的大鼠具有更高的骨矿物质含量（BMC）、骨面积（BA）和骨密度（BMD）；而在喂食 ZnAD 饮食的大鼠中，这些指标最高。饮食对 BMC、BA 和 BMD 的影响与活动水平无关。我们得出结论，摄入补充膳食植酸酶或膳食 Zn 可以增强 Zn 状态，从而增加喂食低 Zn 饮食的大鼠的 BMD、LBM 和自愿体力活动。虽然这些发现证实了骨骼健康容易受到大鼠中度 Zn 缺乏的破坏，但这些新数据表明，如果膳食 Zn 受到限制，补充植酸酶可能对 LBM 和表现活动有益。
