Kim Jihye, Paik Hee Young, Joung Hyojee, Woodhouse Leslie R, Li Shanji, King Janet C
Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, CA 94609, USA.
J Am Coll Nutr. 2007 Feb;26(1):1-9. doi: 10.1080/07315724.2007.10719579.
Previous studies suggest that consumption of predominantly plant-based diets with high phytate content contribute to zinc deficiency by inhibiting zinc absorption. Age of the individual may also affect the ability to maintain zinc homeostasis.
This study was designed to determine the effect of dietary phytate on zinc homeostasis and to evaluate the effect of age on the capacity to maintain the zinc homeostasis with changes in dietary phytate in young and elderly Korean women.
Seven healthy young women (22-24 yr) and 10 healthy elderly women (66-75 yr) were studied consecutively for 3 months in 2 metabolic periods (MP) in two different metabolic units. During MP1 the women consumed a high phytate (HP) diet (P:Zn molar ratio = 23) for 9 days. After a 10 d wash-out period at home eating their usual diets, a lower phytate diet (LP) (P:Zn molar ratio = 10) was fed in MP2 for 9 d. Phytase was added to selected foods in the high phytate diet to reduce the phytate content of the meals in the LP period. The zinc content of both diets was about 6.5 mg/d. Stable isotopes of Zn ((70)Zn) were administered intravenously on d 5 of MP 1 and 2 for measuring endogenous fecal zinc excretion. Plasma samples were also collected on d 5 for measuring plasma zinc concentrations by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). 24 hr urine samples were collected for 5 d and complete fecal samples were collected for 9 d after isotope administration. Fractional zinc absorption (FZA) was calculated from mass balance corrected for endogenous fecal zinc (EFZ) excretion and EFZ was determined by using an isotopic dilution technique. Isotopic ratios for FZA and EFZ were measured by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Statistical analyses were done using ANOVA.
Both the young and elderly women were in negative zinc balance during the HP period. This was due to a significant decrease in FZA and total absorbed zinc (TAZ) with a HP diet (43 vs 22% in young women, 34 vs 20% in elderly women, p < 0.001). EFZ excretion did not differ in the young and elderly women during the LP and HP periods. Dietary phytate did not alter plasma zinc concentrations or and urinary zinc excretion in either group.
Adjustments in zinc homeostasis with an increase in dietary phytate did not differ between young and elderly women in this study.
先前的研究表明，以高植酸盐含量的植物性饮食为主的膳食会通过抑制锌的吸收导致锌缺乏。个体的年龄也可能影响维持锌稳态的能力。
本研究旨在确定膳食植酸盐对锌稳态的影响，并评估年龄对年轻和老年韩国女性在膳食植酸盐变化时维持锌稳态能力的影响。
7名健康年轻女性（22 - 24岁）和10名健康老年女性（66 - 75岁）在两个不同的代谢单元连续进行了2个代谢期（MP）共3个月的研究。在MP1期间，女性食用高植酸盐（HP）饮食（磷：锌摩尔比 = 23）9天。在家中食用平常饮食10天的洗脱期后，在MP2期间喂食低植酸盐（LP）饮食（磷：锌摩尔比 = 10）9天。在高植酸盐饮食中向选定食物添加植酸酶以降低LP期膳食的植酸盐含量。两种饮食的锌含量均约为6.5 mg/天。在MP1和MP2的第5天静脉注射锌的稳定同位素（（70）Zn）以测量内源性粪便锌排泄。在第5天还采集血浆样本，通过电感耦合等离子体原子发射光谱法（ICP - AES）测量血浆锌浓度。同位素给药后收集5天的24小时尿液样本并收集9天的完整粪便样本。根据对内源性粪便锌（EFZ）排泄进行校正的质量平衡计算锌的分数吸收（FZA），并使用同位素稀释技术测定EFZ。通过电感耦合等离子体质谱法（ICP - MS）测量FZA和EFZ的同位素比率。使用方差分析进行统计分析。
在HP期，年轻和老年女性均处于负锌平衡状态。这是由于高植酸盐饮食导致FZA和总吸收锌（TAZ）显著降低（年轻女性中分别为43%对22%，老年女性中为34%对20%，p < 0.001）。在LP期和HP期，年轻和老年女性的EFZ排泄没有差异。膳食植酸盐在两组中均未改变血浆锌浓度或尿锌排泄。
在本研究中，年轻和老年女性在膳食植酸盐增加时锌稳态的调整没有差异。
