Udipi S A, Kirksey A, Roepke J L
Am J Clin Nutr. 1987 Apr;45(4):770-9. doi: 10.1093/ajcn/45.4.770.
Studies of breast-feeding and its adequacy for the infant could be simplified if a single milk sample were representative of nutrient levels during a 24-h period, despite diurnal variation. In this study, free and total folacin levels were measured in samples collected from 27 well-nourished mothers at each infant feeding from 2 wk to 1 yr of lactation. Folacin levels were higher (p less than 0.05) in the afternoon and evening than in the morning; variations decreased as lactation progressed (greater than 8 mo) and paralleled the decreased number of daily feedings. Despite 2- to 3-fold variations in milk folacin levels occur a 24-h period during the first 10 mo of lactation, the level in a single sample obtained at 1300-1450 h was representative (r = 0.74-0.93) of mean folacin concentration in samples obtained from all feedings during a 24-h period.
如果单一的乳汁样本能够代表24小时内的营养水平，而不受昼夜变化影响，那么关于母乳喂养及其对婴儿充足性的研究将会得到简化。在本研究中，对27名营养良好的母亲在哺乳2周龄至1岁期间每次喂养时采集的样本进行了游离和总叶酸水平的测定。下午和晚上的叶酸水平高于早晨（p<0.05）；随着哺乳期的进展（大于8个月），变化幅度减小，且与每日喂养次数的减少平行。尽管在哺乳的前10个月中，24小时内乳汁叶酸水平会出现2至3倍的变化，但在1300-1450时采集的单个样本中的水平可代表（r=0.74-0.93）24小时内所有喂养样本中的平均叶酸浓度。
