{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,11,8]],"date-time":"2026-11-08T11:02:24Z","timestamp":1794135744002,"version":"4.8.0"},"reference-count":44,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2018,11,26]],"date-time":"2018-11-26T00:00:00Z","timestamp":1543190400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Nutrients"],"abstract":"<jats:p>Free amino acids (FAAs) in human milk are indicated to have specific functional roles in infant development. Studies have shown differences between human milk that is expressed at the beginning of a feed (i.e., foremilk) and the remainder of the milk expressed (i.e., hindmilk). For example, it is well established that human hindmilk is richer in fat and energy than foremilk. Hence, exclusively feeding hindmilk is used to enhance weight gain of preterm, low birthweight infants. Whether FAAs occur differently between foremilk and hindmilk has never been reported, but given their bioactive capacities, this is relevant to consider especially in situations where hindmilk is fed exclusively. Therefore, this study analyzed and compared the FAA and total protein content in human foremilk and hindmilk samples donated by 30 healthy lactating women. The total protein content was found to be significantly higher in hindmilk (p &lt; 0.001), whereas foremilk contained a significantly higher total content of FAAs (p = 0.015). With regards to individual FAAs, foremilk contained significantly higher levels of phenylalanine (p = 0.009), threonine (p = 0.003), valine (p = 0.018), alanine (p = 0.004), glutamine (p &lt; 0.001), and serine (p = 0.012) than hindmilk. Although statistical significance was reached, effect size analysis of the milk fraction on FAA levels in milk revealed that the observed differences were only small. To what extent these differences are of physiological importance for infant development remains to be examined in future research.<\/jats:p>","DOI":"10.3390\/nu10121828","type":"journal-article","created":{"date-parts":[[2018,11,26]],"date-time":"2018-11-26T03:24:27Z","timestamp":1543202667000},"page":"1828","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":40,"title":["Short Communication: Differences in Levels of Free Amino Acids and Total Protein in Human Foremilk and Hindmilk"],"prefix":"10.3390","volume":"10","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4416-3114","authenticated-orcid":false,"given":"Joris H. J.","family":"Van Sadelhoff","sequence":"first","affiliation":[{"name":"Danone Nutricia Research, Uppsalalaan 12, 3584 CT Utrecht, The Netherlands"},{"name":"Utrecht Institute for Pharmaceutical Sciences (UIPS), Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dimitra","family":"Mastorakou","sequence":"additional","affiliation":[{"name":"Danone Nutricia Research, Uppsalalaan 12, 3584 CT Utrecht, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6703-4107","authenticated-orcid":false,"given":"Hugo","family":"Weenen","sequence":"additional","affiliation":[{"name":"Danone Nutricia Research, Uppsalalaan 12, 3584 CT Utrecht, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bernd","family":"Stahl","sequence":"additional","affiliation":[{"name":"Danone Nutricia Research, Uppsalalaan 12, 3584 CT Utrecht, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Johan","family":"Garssen","sequence":"additional","affiliation":[{"name":"Danone Nutricia Research, Uppsalalaan 12, 3584 CT Utrecht, The Netherlands"},{"name":"Utrecht Institute for Pharmaceutical Sciences (UIPS), Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Anita","family":"Hartog","sequence":"additional","affiliation":[{"name":"Danone Nutricia Research, Uppsalalaan 12, 3584 CT Utrecht, The Netherlands"},{"name":"Utrecht Institute for Pharmaceutical Sciences (UIPS), Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2018,11,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"30","DOI":"10.1111\/apa.13133","article-title":"Long-term consequences of breastfeeding on cholesterol, obesity, systolic blood pressure and type 2 diabetes: A systematic review and meta-analysis","volume":"104","author":"Horta","year":"2015","journal-title":"Acta Paediatr."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"38","DOI":"10.1111\/apa.13132","article-title":"Breastfeeding and asthma and allergies: A systematic review and meta-analysis","volume":"104","author":"Lodge","year":"2015","journal-title":"Acta Paediatr."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"222","DOI":"10.1097\/MCO.0000000000000367","article-title":"Does infant feeding modulate the manifestation of celiac disease and type 1 diabetes?","volume":"20","author":"Meijer","year":"2017","journal-title":"Curr. Opin. Clin. Nutr. Metab. Care"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"4800","DOI":"10.3390\/nu5124800","article-title":"Amino acid profiles in term and preterm human milk through lactation: A systematic review","volume":"5","author":"Zhang","year":"2013","journal-title":"Nutrients"},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"van Sadelhoff, J.H.J., van de Heijning, B.J.M., Stahl, B., Amodio, S., Rings, E., Mearin, M.L., Garssen, J., and Hartog, A. (2018). Longitudinal variation of amino acid levels in human milk and their associations with infant gender. Nutrients, 10.","DOI":"10.3390\/nu10091233"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"216","DOI":"10.1186\/1471-2431-14-216","article-title":"A systematic review and meta-analysis of the nutrient content of preterm and term breast milk","volume":"14","author":"Gidrewicz","year":"2014","journal-title":"BMC Pediatr."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"81","DOI":"10.1177\/0890334412448841","article-title":"Variation in fat, lactose, and protein composition in breast milk over 24 hours: Associations with infant feeding patterns","volume":"29","author":"Khan","year":"2013","journal-title":"J. Hum. Lact."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1176","DOI":"10.1111\/j.1651-2227.2005.tb02070.x","article-title":"Macronutrient and energy contents of human milk fractions during the first six months of lactation","volume":"94","author":"Saarela","year":"2005","journal-title":"Acta Paediatr."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"129","DOI":"10.1016\/j.enfcli.2008.11.002","article-title":"Hindmilk: A head start in preterm nutrition","volume":"19","author":"Heon","year":"2009","journal-title":"Enferm. Clin."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"191","DOI":"10.1177\/0890334403252490","article-title":"Promoting the exclusive feeding of own mother\u2019s milk through the use of hindmilk and increased maternal milk volume for hospitalized, low birth weight infants (<1800 grams) in nigeria: A feasibility study","volume":"19","author":"Slusher","year":"2003","journal-title":"J. Hum. Lact."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"54","DOI":"10.3389\/fnut.2017.00054","article-title":"Peptides released from foremilk and hindmilk proteins by breast milk proteases are highly similar","volume":"4","author":"Nielsen","year":"2017","journal-title":"Front. Nutr."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"465","DOI":"10.1016\/j.clnu.2014.05.005","article-title":"Rapid measurement of macronutrients in breast milk: How reliable are infrared milk analyzers?","volume":"34","author":"Fusch","year":"2015","journal-title":"Clin. Nutr."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"159","DOI":"10.1177\/0890334408316085","article-title":"Nutrient composition of hindmilk produced by mothers of very low birth weight infants born at less than 28 weeks\u2019 gestation","volume":"24","author":"Bishara","year":"2008","journal-title":"J. Hum. Lact."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"303","DOI":"10.1093\/tropej\/28.6.303","article-title":"Variation in major constituents of fore- and hindmilk of brazilian women","volume":"28","author":"Dorea","year":"1982","journal-title":"J. Trop. Pediatr."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"304","DOI":"10.1093\/ajcn\/32.2.304","article-title":"Uniformity of human milk","volume":"32","author":"Hall","year":"1979","journal-title":"Am. J. Clin. Nutr."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"635","DOI":"10.1093\/ajcn\/40.3.635","article-title":"Studies on human lactation. I. Within-feed and between-breast variation in selected components of human milk","volume":"40","author":"Neville","year":"1984","journal-title":"Am. J. Clin. Nutr."},{"key":"ref_17","first-page":"597","article-title":"Comparison of macronutrient concentration of preterm human milk between two milk expression techniques and two techniques for quantitation of energy","volume":"5","author":"Thomas","year":"1986","journal-title":"J. Pediatr. Gastroenterol. Nutr."},{"key":"ref_18","first-page":"474","article-title":"Hindmilk improves weight gain in low-birth-weight infants fed human milk","volume":"18","author":"Valentine","year":"1994","journal-title":"J. Pediatr. Gastroenterol. Nutr."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1152","DOI":"10.3945\/jn.116.244798","article-title":"Analysis of milk from mothers who delivered prematurely reveals few changes in proteases and protease inhibitors across gestational age at birth and infant postnatal age","volume":"147","author":"Nielsen","year":"2017","journal-title":"J. Nutr."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"7225","DOI":"10.1021\/jf405601e","article-title":"Predicting the important enzymes in human breast milk digestion","volume":"62","author":"Khaldi","year":"2014","journal-title":"J. Agric. Food Chem."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"129","DOI":"10.1159\/000455250","article-title":"Enzymes in human milk","volume":"88","author":"Dallas","year":"2017","journal-title":"Nestle Nutr. Inst. Workshop Ser."},{"key":"ref_22","unstructured":"Canadian Medical Association (1995). Nutrient needs and feeding of premature infants. Nutrition committee, Canadian paediatric society. Can. Med. Assoc. J., 152, 1765\u20131785."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"189","DOI":"10.1016\/j.pcl.2012.09.008","article-title":"Human milk for the premature infant","volume":"60","author":"Underwood","year":"2013","journal-title":"Pediatr. Clin. North Am."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"156","DOI":"10.1111\/j.1442-200X.2007.02336.x","article-title":"Hindmilk and weight gain in preterm very low-birthweight infants","volume":"49","author":"Ogechi","year":"2007","journal-title":"Pediatr. Int."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"198","DOI":"10.1016\/S1875-9572(10)60039-3","article-title":"Protein for preterm infants: How much is needed? How much is enough? How much is too much?","volume":"51","author":"Hay","year":"2010","journal-title":"Pediatr. Neonatol."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1111\/j.1651-2227.1999.tb01298.x","article-title":"Human milk as a carrier of biochemical messages","volume":"88","author":"Bernt","year":"1999","journal-title":"Acta Paediatr."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"749189","DOI":"10.1155\/2012\/749189","article-title":"Glutamine randomized studies in early life: The unsolved riddle of experimental and clinical studies","volume":"2012","author":"Briassouli","year":"2012","journal-title":"Clin. Dev. Immunol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"129","DOI":"10.1079\/BJN19980023","article-title":"Free amino acids in milks of human subjects, other primates and non-primates","volume":"79","author":"Sarwar","year":"1998","journal-title":"Br. J. Nutr."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Cruzat, V., Macedo Rogero, M., Noel Keane, K., Curi, R., and Newsholme, P. (2018). Glutamine: Metabolism and immune function, supplementation and clinical translation. Nutrients, 10.","DOI":"10.20944\/preprints201809.0459.v1"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"856","DOI":"10.1038\/nm0810-856","article-title":"Glutamate joins the ranks of immunomodulators","volume":"16","author":"Hansen","year":"2010","journal-title":"Nat. Med."},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Ganor, Y., and Levite, M. (2012). Glutamate in the Immune System: Glutamate Receptors in Immune Cells, Potent Effects, Endogenous Production and Involvement in Disease. Nerve-Driven Immunity: Neurotransmitters and Neuropeptides in the Immune System, Springer.","DOI":"10.1007\/978-3-7091-0888-8_4"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"2025s","DOI":"10.1093\/jn\/138.10.2025S","article-title":"Nonnutritive effects of glutamine","volume":"138","author":"Roth","year":"2008","journal-title":"J. Nutr."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1186\/2049-1891-4-27","article-title":"The immune modifying effects of amino acids on gut-associated lymphoid tissue","volume":"4","author":"Ruth","year":"2013","journal-title":"J. Anim. Sci. Biotechnol."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"814s","DOI":"10.3945\/ajcn.2009.27462S","article-title":"Metabolism and functions of l-glutamate in the epithelial cells of the small and large intestines","volume":"90","author":"Blachier","year":"2009","journal-title":"Am. J. Clin. Nutr."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"2258","DOI":"10.3945\/jn.115.217661","article-title":"l-glutamate enhances barrier and antioxidative functions in intestinal porcine epithelial cells","volume":"145","author":"Jiao","year":"2015","journal-title":"J. Nutr."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"47","DOI":"10.2174\/1875044301205010047","article-title":"Role of glutamine in protection of intestinal epithelial tight junctions","volume":"5","author":"Rao","year":"2012","journal-title":"J. Epithel. Biol. Pharmacol."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"407","DOI":"10.1203\/PDR.0b013e3181d22cf6","article-title":"Glutathione synthesis rates in early postnatal life","volume":"67","author":"Rook","year":"2010","journal-title":"Pediatr. Res."},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Kim, M.H., and Kim, H. (2017). The roles of glutamine in the intestine and its implication in intestinal diseases. Int. J. Mol. Sci., 18.","DOI":"10.3390\/ijms18051051"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"785","DOI":"10.1067\/mpd.2000.109145","article-title":"Reduced serum amino acid concentrations in infants with necrotizing enterocolitis","volume":"137","author":"Becker","year":"2000","journal-title":"J. Pediatr."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"S78","DOI":"10.1016\/S0899-9007(97)85206-9","article-title":"Glutamine: An essential amino acid for the gut","volume":"12","author":"Soeters","year":"1996","journal-title":"Nutrition"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"F52","DOI":"10.1136\/fn.88.1.F52","article-title":"Intestinal permeability in relation to birth weight and gestational and postnatal age","volume":"88","author":"Fetter","year":"2003","journal-title":"Arch. Dis. Child. Fetal Neonatal Edit."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"236","DOI":"10.1136\/adc.59.3.236","article-title":"Intestinal permeability in the newborn","volume":"59","author":"Weaver","year":"1984","journal-title":"Arch. Dis. Child."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"122","DOI":"10.1007\/s00431-002-1128-0","article-title":"Immunonutrients and neonates","volume":"162","author":"Huang","year":"2003","journal-title":"Eur. J. Pediatr."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"2585S","DOI":"10.1093\/jn\/131.9.2585S","article-title":"Glutamine in the fetus and critically ill low birth weight neonate: Metabolism and mechanism of action","volume":"131","author":"Neu","year":"2001","journal-title":"J. Nutr."}],"container-title":["Nutrients"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-6643\/10\/12\/1828\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T15:32:00Z","timestamp":1760196720000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-6643\/10\/12\/1828"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2018,11,26]]},"references-count":44,"journal-issue":{"issue":"12","published-online":{"date-parts":[[2018,12]]}},"alternative-id":["nu10121828"],"URL":"https:\/\/doi.org\/10.3390\/nu10121828","relation":{},"ISSN":["2072-6643"],"issn-type":[{"value":"2072-6643","type":"electronic"}],"subject":[],"published":{"date-parts":[[2018,11,26]]}}}