The purpose of this study was to evaluate the circadian variation of human milk macronutrients and energy content depending upon pregnancy duration. One hundred eighty fresh human milk samples from 45 mothers (27 of preterm and 18 of full-term newborns) were collected on a single day chosen between the 14th to 16th day after delivery. The samples were taken four times per day at 12 PM, 6 PM, 12 AM and 6 AM. Only lactating women, who could not breastfeed their hospitalized newborns and expressed milk by breast pump, were enrolled in the study. Human milk macronutrient composition and energy count were evaluated by mid-infrared spectrophotometry. Significant differences in macronutrient content were observed between 6 AM and 12 PM for mean protein content (t = − 4.62, df = 44, p < 0.001), for mean fat content (t = − 2.10, df = 44, p = 0.04) and for mean energy content (t = − 2.24, df = 44, p = 0.03); between 6 AM and 6 PM for mean protein content (t = − 2.41, df = 43, p = 0.02), for mean fat content (t = − 3.76, df = 43, p = 0.001) and for mean energy content (t = − 3.85, df = 43, p < 0.001); between 12 PM and 12 AM for mean protein content (Wilcoxon test V = 75.5, p = 0.001), for mean fat content (t = 2.50, df = 44, p = 0.02) and for mean energy content (t = 2.74, df = 44, p = 0.01); between 6 PM and 12 AM for mean protein content (V = 229, p = 0.02), for mean fat content (t = 4.39, df = 43, p < 0.001) and for mean energy content (t = − 4.57, df = 43, p < 0.001). The average content of carbohydrates did not change significantly during the 24 h. The samples of preterm newborns’ mothers had more apparent diurnal fluctuations in macronutrient content. Our study revealed significant diurnal variations in protein and fat in human milk, and these circadian fluctuations were more apparent in the milk of mothers of preterm infants.

中文翻译：

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横断面研究显示，人乳中大量营养素的昼夜节律变化取决于妊娠持续时间。

这项研究的目的是评估取决于怀孕时间的人乳中大量营养素和能量含量的昼夜变化。在分娩后第14天到第16天之间选择的一天，收集了来自45位母亲（早产27位和足月新生儿18位）的180份新鲜人乳样品。每天在12 PM，6 PM，12 AM和6 AM采集四次样品。该研究仅纳入了那些无法哺乳住院新生儿并且无法通过吸乳器表达乳汁的哺乳期妇女。通过中红外分光光度法评估了母乳中的大量营养素组成和能量计数。对于平均蛋白质含量（t = − 4.62，df = 44，p <0.001），对于平均脂肪含量（t = − 2.10，df = 44，p = 0），大型营养素含量之间存在显着差异。04）和平均能量含量（t = − 2.24，df = 44，p = 0.03）; 平均蛋白质含量（t = − 2.41，df = 43，p = 0.02），平均脂肪含量（t = − 3.76，df = 43，p = 0.001）和平均能量含量（t）在6 AM和6 PM之间=-3.85，df = 43，p <0.001）；平均蛋白质含量（Wilcoxon测试V = 75.5，p = 0.001），平均脂肪含量（t = 2.50，df = 44，p = 0.02）和平均能量含量（t = 2.74，df）在12 PM和12 AM之间= 44，p = 0.01）；平均蛋白质含量（V = 229，p = 0.02），平均脂肪含量（t = 4.39，df = 43，p <0.001）和平均能量含量（t = − 4.57，df = 43，p ＜0.001）。碳水化合物的平均含量在24小时内没有显着变化。早产儿母亲的样品中常量营养元素含量的昼夜波动更大。