Krebs N F, Reidinger C J, Miller L V, Hambidge K M
Department of Pediatrics, University of Colorado School of Medicine, Denver 80262, USA.
Pediatr Res. 1996 Apr;39(4 Pt 1):661-5. doi: 10.1203/00006450-199604000-00017.
The needs for dietary zinc are adequately met by most fully breast-fed infants despite relatively low zinc intakes in relation to estimated requirements. The objective of this study was to use stable isotope techniques to evaluate how zinc retention is achieved in normal fully breast-fed infants. Nine male infants, aged 2-5 mo, were fed expressed human milk labeled with 70Zn over a 24-h period. Complete fecal collections were obtained for 8 d. On d 4-7, a metabolic period was initiated which included test weighing and milk sampling, to measure zinc intake, and daily urine collections. Isotopic enrichment of fecal and urine samples was determined by fast atom bombardment mass spectrometry. Results included a mean (+/- SD) dietary zinc intake of 17.8 +/- 6.6 mumol/d; fractional absorption of 0.54 +/- 0.075; and total absorbed zinc of 9.5 +/- 3.5 mumol/d. Mean endogenous fecal zinc, determined on seven infants by isotope dilution, was 4.7 +/- 2.3 mumol/d, which resulted in a mean net absorption of 4.8 +/- 3.4 mumol/d. The results of the study indicated that, for fully breast-fed infants, it is the combination of a relatively high fractional absorption and efficient conservation of intestinal endogenous zinc that results in zinc retention adequate to meet the demands of growth in the face of modest intake.
尽管相对于估计需求量而言，锌摄入量较低，但大多数纯母乳喂养的婴儿对膳食锌的需求仍能得到充分满足。本研究的目的是使用稳定同位素技术评估正常纯母乳喂养婴儿是如何实现锌潴留的。9名年龄在2至5个月的男婴在24小时内喂食了用70Zn标记的人乳。连续8天收集完整的粪便。在第4至7天，开始一个代谢期，包括试重和采集乳汁以测量锌摄入量，以及每天收集尿液。通过快原子轰击质谱法测定粪便和尿液样本的同位素富集情况。结果包括平均（±标准差）膳食锌摄入量为17.8±6.6μmol/d；吸收率为0.54±0.075；总吸收锌量为9.5±3.5μmol/d。通过同位素稀释法对7名婴儿测定的平均内源性粪便锌为4.7±2.3μmol/d，这导致平均净吸收量为4.8±3.4μmol/d。研究结果表明，对于纯母乳喂养的婴儿来说，相对较高的吸收率和肠道内源性锌的有效保存相结合，使得在摄入量适度的情况下仍能实现足够的锌潴留以满足生长需求。
