Differences in the Composition of Preterm and Term Human Milk during Early Lactation

Abstract

SummaryThe composition of human milk from mothers delivering prematurely (PT) and at term (T) was studied over the first weeks of lactation. Complete 24 h milk expressions were obtained by electric pump at weekly or biweekly intervals through 44 wk conceptual age (120 samples from 20 PT mothers and 28 samples from 7 T mothers). PT milk was found to contain significantly higher concentrations than T milk of the following nutrients: total nitrogen, protein nitrogen, sodium, chloride, magnesium and iron. No differences were found between T and PT milk for nonprotein nitrogen, volume, solids, total calories, lactose, fat, fatty acids, potassium or calcium. The nutrients supplied to a 33 wk preterm infant fed 200 ml/kg/day of "average" PT milk were in excess of theoretic intrauterine requirements for all substrates except calcium and phosphorus. PT human milk is theoretically more suitable for the premature infant than either mature or term human milk, but may be deficient in specific nutrients for the very low birth weight baby. SpeculationThe compositional differences in preterm milk (increased protein and mineral content) are generally characteristic of colostrum. These changes may therefore reflect a prolonged colostral phase in premature mothers who are establishing lactation by artificial means during periods of emotional stress. Thus, the changes denoted for preterm milk may reflect the circumstances surrounding the onset of lactation rather than the nutritional requirements of the preterm infant.Controversy persists regarding the propriety of human milk for the feeding of preterm infants. Although insufficient data are available to determine exact nutritional requirements of the premature baby (16), Fomon et al. (10) have appropriately questioned the adequacy of mature breast milk in relation to estimated needs. While providing theoretically beneficial nonnutritional factors, mature human milk may be quantitatively deficient in protein, calcium, sodium and possibly other nutrients for the premature (10). Clinical studies of premature infants fed mature breast milk have yielded conflicting results (8,14,19,25), although the data generally indicate that mature human milk does not provide optimal nutritional support to the low birth weight infant.Recent investigations offer intriguing data which indicate that the composition of milk from mothers delivering prematurely differs from that of term mothers during the early weeks of lactation. Atkinson et al. (2) and Gross et al. (15) have confirmed a higher concentration of protein nitrogen in preterm milk, while Gross et al. also found an increased level of sodium in the premature mothers' milk. These findings suggest that preterm milk is theoretically more suitable for the premature infant than is mature milk. The present investigation was performed to assess, in a comprehensive fashion, the composition of milk from mothers delivering prematurely and at term over the same period of lactation. Further, the study was designed to control for many variables known to af...

Mother's iron status, breastmilk iron and lactoferrin – are they related?

“…The values reported in different studies may be due in part to differences in sampling procedures as well as stage of lactation. Iron content of human milk is highest in early transitional milk (0.97 mg/l) (Lauber and Reinhardt, 1979) but decrease steadily during lactation, reaching a level of approximately 0.35 mg/l at 1 month of lactation to 0.20 mg/l at 6 months (Lemons et al, 1982;Lonnerdal, 1984). The diurnal variation in iron content of breastmilk tend to parallel those reported for fat content with significantly lower mean values in the early morning feeding compared to late evening feeding (Hall, 1979;Fransson and Lonnerdal, 1980).…”

Preterm human milk composition: a systematic literature review

“…(33) Average 28·3 -Days 6-8, 13-15 N, lipid, lactose, E* Bauer & Gerss (6) 23-33 102 1-8 weeks Pro, lipid, carbohydrate, E Beijers et al (34) 25·7-36 45 1, 2 and 4 weeks N Beijers & Schaafsma (35) <36 65 Days 0-5, 6-14, 15-55 Lipid Chessex et al (36) Average 30·3 1 1 -N, lipid, carbohydrate, E* Corvaglia et al (13) 26-32 55 Day 10 N, lipid Ehrenkranz et al (37) 26-33 21 Days 2, 7, 14, 28, 42 Lipid Faerk et al (38) <32 (average 28) 101 1-10 weeks N, lipid, carbohydrate, E* Gross et al (20) 27-32 (43) 26-36 58 Days 1-28 N Maas et al (44) 25-29 79 1-11 weeks N, lipid, lactose, carbohydrate, E* Saarela et al (45) Average 31·4 36 1 week, 1, 2, 3, 4, 5, 6 months N, lipid, lactose, E* Sann et al (46) 26-35 41 < 6, 7-14, >15 d Pro, lipid, lactose Silber et al (47) Average 29·6 5 Days 9-17 N, lipid, lactose, E Stevens (48) 34-36 weeks 7 Days 3-25 N E, energy; *, calculated; Pro, protein. (34) †, Ehrenkranz (37) , Faerk (38) , Gross (20) *, Guerrini (39) , Jitta (40) , Lemons (16) †, Lucas (43) *, Saarela (45) , Sann (46) , Stevens (48) Kjeldahl (16,34) Kjeldahl without NPN correction (18,20,33,45,48) Micro Kjeldahl (17) Semi-micro Kjeldahl (21) Semi-micro Kjeldahl without NPN correction (32,43) Biuret (46) Lowry-Peterson (6) IR spectrophotometry …”

“…1·46-2·40 Folch (37,46) Roese-Gottlieb (20,44) Colorimetry (16,18,33) Gerber (13) De la Huerga (39) Jeejeebhoy (47) Van de Kamer (17) Creamatocrit (40) IR spectrophotometry (13) 3·63 3·49-4·30 Lactose: Chromatography (16,46) Boehringer lactose assay kit (18,44) Unidentified (40) Unidentified (47) Unidentified (20) Total carbohydrate: Carbohydrate by difference (44) Beckman Glucose Analyzer (17) 5·94 7·11…”

“…Atwater specific factor system (20) Atwater general factor system (45) Heats of combustion factors (18,33,38,40) Bomb calorimetry (6,16,17) 267·8 205·0-309·6 64·0 49·0-74·0 (34) †, Corvaglia (13) , Ehrenkranz (37) , Gross (20) *, Guerrini (39) , Jitta (40) , Lemons (16) †, Lepage (42) †, Lucas (43) *, Maas (44) †, Sann (46) , Stevens (48) , Silber (47) † Kjeldahl (16,34,42) Kjeldahl with NPN not accounted for (13,18,20,33,44,47,48) Micro Kjeldahl (17) Semi-micro Kjeldahl (21) Semi-micro Kjeldahl without NPN (32,43) Biuret (46) Lowry-Peterson (6) IR spectrophotometry (13) Esbach/Bogg (40) 1·67…”

“…Common practice is to fortify on an assumed average preterm breast milk composition (6,7,9) ; however, significant variation in the macronutrient content of breast milk exists between and within mothers (6,(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) , reflected by wide variations in macronutrient values derived by studies and adopted by neonatal intensive care units and industry to fortify milk, raising concerns that this practice may lead to undernourishment of some infants and over-nourishment of others (7) . The lack of a globally accepted reference 'assumed' preterm breast milk composition inhibits standardised reporting of nutritional intakes, making it difficult for clinicians and researchers to assess the adequacy of nutritional intakes and the role of nutrition in growth and developmental preterm outcomes.…”