Background

Complementary feeding of breastfed infants with foods high in bioavailable zinc (Zn) can help meet physiological requirements for Zn. Some infant cereals contain high concentrations of phytic acid (PA) and calcium (Ca) that may reduce absorbable Zn.

Objectives

This study measured PA, Zn and Ca concentrations in selected infant cereals sold in Canada and investigated the effects of dietary PA and Ca at concentrations present in infant cereals on Zn bioavailability in rats.

Methods and results

Male Sprague-Dawley rats (36-day old) were fed a control diet containing normal Zn (29.1 mg/kg) and Ca (4.95 g/kg) or six test diets (n = 12/diet group). Test diets were low in Zn (8.91–9.74 mg/kg) and contained low (2.16–2.17 g/kg), normal (5.00–5.11 g/kg) or high (14.6–14.9 g/kg) Ca without or with added PA (8 g/kg). After 2 weeks, rats were killed and Zn status of the rats was assessed. PA, Zn and Ca concentrations in infant cereals (n = 20) differed widely. PA concentrations ranged from undetectable to 16.0 g/kg. Zn and Ca concentrations ranged from 7.0–29.1 mg/kg and 0.8–13.4 g/kg, respectively. The [PA]/[Zn] and [PA × Ca]/[Zn] molar ratios in infants cereals with detectable PA (16 of 20 cereals) ranged from 22–75 and 0.9–14.9 mol/kg, respectively, predicting low Zn bioavailability. Body weight, body composition (lean and fat mass), right femur weight and length measurements and Zn concentrations in serum and femur indicated that diets higher in Ca had a more pronounced negative effect on Zn status of rats fed a PA-supplemented diet. Addition of PA to the diet had a greater negative effect on Zn status when Ca concentration in the diet was higher.

Conclusion

These results show that, in rats, higher concentrations of dietary Ca and PA interact to potentiate a decrease in bioavailable Zn and may suggest lower Zn bioavailability in infant cereals with higher PA and Ca concentrations.

中文翻译：

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钙会加剧植酸对大鼠锌生物利用度的抑制作用。

背景

给母乳喂养的婴儿补充富含生物可利用锌 (Zn) 的食物有助于满足对锌的生理需求。一些婴儿谷物含有高浓度的植酸 (PA) 和钙 (Ca)，可能会降低可吸收的锌。

目标

本研究测量了在加拿大销售的选定婴儿谷物中 PA、Zn 和 Ca 的浓度，并研究了婴儿谷物中存在的膳食 PA 和 Ca 浓度对大鼠锌生物利用度的影响。

方法和结果

雄性 Sprague-Dawley 大鼠（36 天大）被喂食含有正常锌（29.1 毫克/千克）和钙（4.95 克/千克）的对照饮食或六种测试饮食（n = 12/饮食组）。测试日粮中锌含量低 (8.91–9.74 mg/kg) 并且含有低 (2.16–2.17 g/kg)、正常 (5.00–5.11 g/kg) 或高 (14.6–14.9 g/kg) Ca，不添加或添加PA（8克/公斤）。2周后，杀死大鼠并评估大鼠的锌状态。婴儿谷物（n = 20）中的 PA、Zn 和 Ca 浓度差异很大。PA 浓度范围从检测不到到 16.0 g/kg。Zn 和 Ca 的浓度范围分别为 7.0–29.1 mg/kg 和 0.8–13.4 g/kg。含可检测 PA 的婴儿谷物（20 种谷物中的 16 种）中的 [PA]/[Zn] 和 [PA × Ca]/[Zn] 摩尔比范围分别为 22-75 和 0.9-14.9 mol/kg，预测低锌生物利用度。体重，身体成分（瘦肉和脂肪量），右股骨重量和长度测量值以及血清和股骨中的锌浓度表明，高钙饮食对喂食 PA 补充饮食的大鼠的锌状态有更明显的负面影响。当日粮中的钙浓度较高时，日粮中添加 PA 对锌状态有更大的负面影响。

结论

这些结果表明，在大鼠中，较高浓度的饮食 Ca 和 PA 相互作用以增强生物可利用锌的减少，并且可能表明具有较高 PA 和 Ca 浓度的婴儿谷物中锌的生物利用度较低。