Supplementary Material for: Influence of Feeding Types during the First Months of Life on Calciuria Levels in Healthy Infants: A Secondary Analysis from a Randomized Clinical Trial

<b><i>Background/Aims:</i></b> Dietary factors can modify calciuria. We aim to investigate urinary calcium excretion in healthy infants according to their protein. <b><i>Methods:</i></b> Secondary data analysis from a randomized clinical trial where healthy term infants were randomized after birth to a higher (HP) or lower (LP) protein content formula that was consumed until age 1 year. A non-randomized group of breastfed (BF) infants was used for reference. Anthropometry, dietary intakes and calciuria (calcium/creatinine ratios) from spot urine samples were assessed at ages 3 and 6 months. At 6 months, the kidney volumes were assessed using ultrasonography, and the serum urea and creatinine levels were determined. <b><i>Results:</i></b> BF infants showed the highest calciuria levels, followed by the HP and the LP groups (<i>p</i> &lt; 0.001 for all comparisons). Either protein intakes or formula types modulated the calciuria in linear regression models adjusted for other influencing dietary factors. The usual cut-off values classified 37.8% (BF), 16.8% (HP) and 4.9% (LP) of the infants as hypercalciuric. <b><i>Conclusions:</i></b> Feeding types during the first months of life affect calciuria, with BF infants presenting the highest levels. We propose new cut-off values, based on feeding types, to prevent the overestimation in hypercalciuria diagnoses among BF infants.

<b><i>背景与目的：</i></b> 膳食因素可影响尿钙排泄（calciuria）。本研究旨在探究健康婴儿的尿钙排泄水平与蛋白质摄入的关联。<b><i>方法：</i></b> 本研究为一项随机对照试验（randomized clinical trial）的二次数据分析，纳入健康足月婴儿，于出生后随机分为高蛋白质（HP）配方奶组与低蛋白质（LP）配方奶组，两组均持续喂养至婴儿1岁；另设非随机的母乳喂养（BF）婴儿组作为参照组。分别于婴儿3月龄与6月龄时，对其体格测量指标、膳食摄入情况以及随机尿样本的尿钙排泄水平（以钙/肌酐比值（calcium/creatinine ratios）表征）进行评估；于6月龄时采用超声检查（ultrasonography）评估肾脏体积，并检测血清尿素（serum urea）与肌酐（creatinine）水平。<b><i>结果：</i></b> 母乳喂养组婴儿的尿钙排泄水平最高，其次为高蛋白质配方奶组与低蛋白质配方奶组，所有组间比较的p值均<0.001。在校正其他膳食影响因素的线性回归模型中，蛋白质摄入量与配方奶类型均可调节尿钙排泄水平。采用常规临界值判定时，分别有37.8%的母乳喂养组、16.8%的高蛋白质配方奶组与4.9%的低蛋白质配方奶组婴儿被归类为高钙尿症（hypercalciuric）患者。<b><i>结论：</i></b> 婴儿出生后最初数月的喂养方式可影响尿钙排泄水平，其中母乳喂养组婴儿的尿钙排泄水平最高。本研究提出基于喂养类型的新型临界值，以避免对母乳喂养婴儿的高钙尿症诊断出现过度评估。