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      Circadian changes in the composition of human milk macronutrients depending on pregnancy duration: a cross-sectional study

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          Abstract

          Background

          The purpose of this study was to evaluate the circadian variation of human milk macronutrients and energy content depending upon pregnancy duration.

          Methods

          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.

          Results

          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.

          Conclusions

          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.

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          Most cited references29

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          Degree of breast emptying explains changes in the fat content, but not fatty acid composition, of human milk.

          We compared within and between breastfeed changes in milk fat to short-term rates of milk synthesis and degree of breast emptying (measured using the Computerized Breast Measurement system) over two 24 h periods for five lactating mothers. The fat content (f) of fore and hind milk samples increased more steeply as the breast was progressively emptied by the infant (degree of emptying, d, range 0-1; f = 21.59 + 9.38d + 70.99d2; P < 0.0001; r2 = 0.68; n = 154). For the nine individual breasts, between 41-95% of the variance of the fat content of milk was explained by degree of breast emptying. We argue that this relationship explains differences in the circadian rhythm of the fat content of milk and allows the accurate calculation of the average fat content of milk consumed by infants (37-66 g/l for the nine individual breasts). The fatty acid composition of the fore and hind milk samples was determined for four of the mothers. We observed within and between breastfeed variability in the relative proportions of the seven major fatty acids of milk fat and these changes are discussed with reference to the control of fat synthesis in the human mammary gland.
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            Human Milk Nutrient Composition in the United States: Current Knowledge, Challenges, and Research Needs

            Abstract Human milk is considered to be the ideal food for infants. Accurate, representative, and up-to-date nutrient composition data of human milk are crucial for the management of infant feeding, assessment of infant and maternal nutritional needs, and as a guide for developing infant formula. Currently in the United States, the nutrient profiles of human milk can be found in the USDA National Nutrient Database for Standard Reference, and in books or review articles. Nonetheless, these resources all suffer major drawbacks, such as being outdated, incomplete profiles, limited sources of data, and uncertain data quality. Furthermore, no nutrient profile was developed specifically for the US population. The purposes of this review were to summarize the current knowledge of human milk nutrient composition from studies conducted in the United States and Canada, and to identify the knowledge gaps and research needs. The literature review was conducted to cover the years 1980–2017, and 28 research papers were found containing original data on macronutrients and micronutrients. Most of these 28 studies were published before 1990 and mainly examined samples from small groups of generally healthy lactating women. The experimental designs, including sampling, storage, and analytic methods, varied substantially between the different studies. Data of several components from these 28 studies showed some consistency for 1–6 mo postpartum, especially for protein, fat, lactose, energy, and certain minerals (e.g., calcium). The data for 7–12 mo postpartum and for other nutrients are very scarce. Comprehensive studies are required to provide current and complete nutrient information on human milk in the United States.
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              Studies on human lactation. I. Within-feed and between-breast variation in selected components of human milk.

              Within-feed and between-breast differences in the concentrations of sodium, potassium, chloride, calcium, magnesium, lipid, protein, lactose, glucose, urea nitrogen, creatinine, zinc, and copper were examined in milk samples from 10 women. The average lipid content doubled in the interval from the beginning of the feed to the end. The composition of the aqueous phase of milk, as determined by the major osmotically active constituents, did not vary significantly within the feed. For these components as well as for lipid a small mid-feed sample of milk gave the same mean composition as the pooled, pumped contents of one breast suggesting that such a sample is adequate for determination of milk composition in population studies. Sporadic, inconsistent differences in the composition of the milk from the right and left breasts were observed. It is suggested that mastitis may contribute to these differences. It is recommended that samples routinely be taken from both breasts and analyzed for sodium and chloride to rule out episodes of mastitis or other local phenomena which sporadically alter milk composition.
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                Author and article information

                Contributors
                ieva.paulaviciene@mf.vu.lt
                Journal
                Int Breastfeed J
                Int Breastfeed J
                International Breastfeeding Journal
                BioMed Central (London )
                1746-4358
                25 May 2020
                25 May 2020
                2020
                : 15
                : 49
                Affiliations
                [1 ]GRID grid.6441.7, ISNI 0000 0001 2243 2806, Clinic of Children Diseases, Institute of Clinical Medicine, Faculty of Medicine, , Vilnius University, ; Vilnius, Lithuania
                [2 ]GRID grid.6441.7, ISNI 0000 0001 2243 2806, Vilnius University Hospital Santaros Klinikos, ; Vilnius, Lithuania
                [3 ]GRID grid.6441.7, ISNI 0000 0001 2243 2806, Department of Human and Medical Genetics, Institute of Biomedical Sciences, Faculty of Medicine, , Vilnius University, ; Vilnius, Lithuania
                [4 ]GRID grid.9424.b, ISNI 0000 0004 1937 1776, Department of Information Systems, Faculty of Fundamental Sciences, , Vilnius Gediminas Technical University, ; Vilnius, Lithuania
                [5 ]State Research Institute, Center of Innovative Medicine, Department of Immunology, Vilnius, Lithuania
                Author information
                http://orcid.org/0000-0002-6813-2363
                Article
                291
                10.1186/s13006-020-00291-y
                7249354
                32450886
                a295709b-5436-45bd-900a-4a6750349b35
                © The Author(s) 2020

                Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

                History
                : 4 September 2019
                : 11 May 2020
                Categories
                Research
                Custom metadata
                © The Author(s) 2020

                Obstetrics & Gynecology
                circadian variation,human milk,macronutrient,mid-infrared spectrophotometry

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