The choline content of human breast milk expressed during the first few weeks of lactation

Abstract

Choline is a conditionally essential nutrient required by the human body for synthesis of the neurotransmitter acetylcholine and the phospholipids phosphatidylcholine (PtdCho), lysophosphatidylcholine, sphingomyelin (SM) and plasmalogen. It also undergoes irreversible oxidation to form betaine, a major source of methyl groups. Betaine is excreted by human infants in large quantities (up to 1 mol/mol creatinine) during the first year reaching a maximum at 2-3 months of age. Since the betaine content of breast milk is very low and choline is the only known endogenous source of betaine, the supply of dietary choline to neonates may be critical particularly for premature babies whose intake may be restricted in the early days of life [ 11. Some premature babies receive expressed breast milk and we have measured the choline content, distribution and temporal variation to determine whether its supply is sufficient. Choline is present in breast milk as free choline (Cho), phosphorylcholine (PC), glycerophosphocholine (GPC), PtdCho and SM [2]. Previous studies have not considered the contributions of GPC and PC [3].Milk samples were obtained from the Neonatal Intensive Care Unit of the Royal London Hospital. Samples were expressed by mothers and then frozen at -20°C until such time as the baby required the milk. At that time samples were defrosted and an aliquot taken for preparation for 'H nmr spectroscopy.The water soluble metabolites (Cho, PC and GPC) were measured in perchloric acid extracts of the milk, neutralised with KOH. Samples were run at pH values of 2 and 7 to distinguish the three metabolites from each other and from other metabolites with similar chemical shift values such as carnitme. Following lyophilisation the samples were dissolved in 0.6 ml 'H20 with 50 p1 lOmM fiunarate and 20 p1 20 mM 3-(trimethylsilyl)-2,2,3,3-tetradeuteropropionate (TSPQ) for field locking, quantification and chemical shift referencing respectively. The samples were run at room temperature in a Jeol GSXSOO or Bruker AM400 spectrometer using a single pulse sequence (30" pulse angle, 2.73 s acquisition time and a 5 s recycling time).The choline containing phospholipids were measured in chloroform extracts. After separation the lower chloroform layer was evaporated under nitrogen, redissolved in 0.6 ml C2HCI3:C2H3O2H (2: 1) containing tetramethykhe (TMS; 0.03% v h in C2HCl3) and 0.3 mM 1,3,5-trichlorobee as the chemical shift reference and quantification standard respectively. The samples were run as descriied above. Figure 1 shows the concentration of choline metabolites in the milk expressed by one mother. This is qualitatively similar to the pattern observed for milk fiom 4 other mothers who have expressed milk over a similar time period and whose babies were born at between 28 and 37 weeks gestation. Until about one week after birth the total choline content is relatively low and is mostly present as Cho, PtdCho and SM. After that the total choline concentration rises quite markedly with the greatest increase being shown by GPC ...

Dietary Choline Intake: Current State of Knowledge Across the Life Cycle

“…Milk choline is either transported from the maternal circulation or obtained through de novo synthesis via the PEMT pathway in the mammary gland [ 124 , 125 ]. It has been described that the concentrations of total choline in human milk increase almost two-fold during the first week after birth and remain relatively constant thereafter in mature milk [ 115 , 116 , 126 ].…”

“…[ 138 ]. There is also range of different methodologies used to analyze milk choline, which include radio-enzymatic assay, detection using proton nuclear magnetic resonance, isolation and quantification using gas chromatography, and high-performance liquid chromatography coupled with mass spectrometry [ 119 , 121 , 126 , 127 ]. One advantage of using radiolabeled or stable isotopes is the allowance for simultaneous detection and analysis of choline metabolites [ 139 , 140 , 141 ].…”

Dietary Reference Values for choline

“…Infants excrete high amounts of betaine in their urine, up to 1.5 mmol/mmol creatinine (1.55 g/g creatinine) during the first year of life, with a maximum at the age of 2–3 months and a decrease to 0.2 mmol/mmol creatinine at 1 year (Holmes et al., ). During the first 10 days of life, a urinary excretion of betaine of 27.4 ± 2.8 μmol/kg bw per day (3.2 ± 0.3 mg/kg per day; mean ± SEM) was reported in 27 infants.…”

“…During the first 10 days of life, a urinary excretion of betaine of 27.4 ± 2.8 μmol/kg bw per day (3.2 ± 0.3 mg/kg per day; mean ± SEM) was reported in 27 infants. At that age, no dietary source of betaine is available (Holmes et al., ), besides human milk with its low concentration of betaine (360–515 μg/L) (Davenport et al., ). In the newborn period, urinary excretion of betaine may be higher than choline intake (Davies et al., ).…”

Changes in the choline content of human breast milk in the first 3 weeks after birth

“…1) [16,Zeisel,personal communication]. Later our group [13] and Zeisel's [14] reported relatively high levels of these esters in mature human milk.…”