Studies in human lactation 3: molybdenum and nickel in human milk during the first month of lactation

Molybdenum and nickel were measured in 62 and 46 samples, respectively, of human milk collected from 13 women between delivery and 38 d postpartum. Trace elements were analyzed by graphite-furnace atomic absorption spectrophotometry, with standard additions to whole milk without pretreatment. Molybdenum levels (mean +/- SD) fell from 15.0 +/- 6.1 ng/mL on day 1 to an apparently constant level of 1-2 ng/mL by 1 mo. Nickel concentrations did not change with time; the overall mean was 1.2 +/- 0.4 ng/mL. Intakes of the elements by infants were calculated with test-weighing data on the fully breast-fed infants of these same mothers. By 1 mo, the average daily intake of molybdenum was 1.5 micrograms; that of nickel was 0.8 microgram.     

Studies in human lactation: milk volume and nutrient composition during weaning and lactogenesis

Concentrations and secretion rates of macronutrients and major ions in human milk during lactogenesis (birth to 8 d) and late lactation (greater than 6 mo postpartum) are reported. Postpartum changes in lactose, sodium, and chloride concentrations signalled closure of the paracellular pathway during days 1-2. From days 2 to 4 postpartum, initiation of copious milk secretion was accompanied by significant increases in citrate, free phosphate, glucose, and calcium concentrations and a decrease in pH. During weaning, significant changes in milk protein, lactose, chloride, and sodium concentrations were observed only when milk volume fell below 400 mL/d; more than one feed per day was necessary to maintain milk secretion. Temporal changes in the concentration of other milk components, except glucose and magnesium, were not different in weaning and non-weaning women. Differences between the relation of milk volume and composition during lactogenesis and weaning suggest that volume is differently regulated in the two periods.     

Studies in human lactation: zinc, copper, manganese and chromium in human milk in the first month of lactation

Zinc, copper, manganese and chromium were measured in a total of 259 samples of human milk from 11 women from day of delivery to 31 days postpartum. Milk intakes by their fully breast-fed infants were calculated from 24-h test-weighing measurements. Zinc was analyzed by flame atomic absorption spectrophotometry, and the other elements by graphite furnace atomic absorption. Mean (+/- SD) concentrations declined from a maximum of 11.5 +/- 4.7 micrograms/ml at 2 days to 2.98 +/- 0.78 micrograms/ml at 28 +/- 3 days. Changes in the other three elements were irregular. The average copper concentration declined from 0.6 +/- 0.12 micrograms/ml on day 5 to 0.41 +/- 0.04 micrograms/ml at 28 days. Manganese levels decreased from a mean of 5.4 +/- 1.6 ng/ml on day 1 to 2.7 +/- 1.6 ng/ml on day 5; from 8 to 28 days there was little change, the overall mean being 3.7 +/- 2.2 ng/ml. The average concentration of chromium over the whole period was 0.27 +/- 0.10 ng/ml. Average daily intakes of the elements, by the infants, over the one month period were: zinc, 2.0 mg; copper, 0.25 mg; manganese, 2.0 micrograms; chromium, 150 ng.     

Studies in human lactation: milk composition and daily secretion rates of macronutrients in the first year of lactation

Time-dependent changes in milk composition and secretion from pregnancy through greater than or equal to 6 mo of exclusive breast-feeding were studied in 13 multiparous women. Concentrations and secretion rates of lipid, lactose, protein, sodium, chloride, potassium, total calcium, ionized calcium, magnesium, glucose, citrate, inorganic phosphate, creatinine, and urea and pH were analyzed longitudinally from day 6 until weaning commenced. The composition of the antepartum secretion was related to the permeability of the junctional complexes between mammary cells. Significant increases in lactose, glucose, pH, and ionized calcium and significant decreases in protein, sodium, potassium, chloride, and calcium concentrations were observed between 1 and 6 mo. Significant differences among individuals, which persisted through lactation, were observed for the concentrations of sodium, potassium, chloride, and inorganic phosphate. The amount of lactose, ionized calcium, and magnesium transferred to the infant was also characteristic of each mother-infant pair. Our data imply that lactation performance is determined in the first month postpartum.     

Polychlorinated biphenyls and organochlorine pesticides in milk of Norwegian women during lactation

Milk samples of 14 women were analyzed for PCBs (polychlorinated biphenyls),p,p-DDE, and HCB (hexachlorobenzene) during 11 intervals of a 120 day-lactation period. A general downward trend in residue levels was evident, and a statistically significant decline was observed for residue levels of PCBs (P<0.01) and HCB (P=0.02) on the milk fat basis. Primipara (n=9) had from 1.5 to 2.1 times higher mean residue levels than mothers nursing their second or third child (n=9). Significant declines in residue levels during lactation of the first child were found, while no pronounced changes in residue levels were observed during lactation of the second or third child. Overall, residue levels in this study were lower than corresponding levels found earlier in Norway, and within the range of the corresponding levels found in another Norwegian human milk survey done at the same time.     

Studies in human lactation: secretion of zinc, copper, and manganese in human milk

Zinc, copper, and manganese were measured in milk samples collected longitudinally from 13 highly selected, healthy lactating women. Samples were obtained at least weekly up to 1 mo and then monthly up to 18 mo postpartum or to weaning. Zn concentrations in milk declined throughout lactation from 71.9 +/- 18.3 mumol/L (means +/- SD) at 7 d to 44.3 +/- 10.7 mumol/L at 1 mo and 7.64 +/- 4.59 mumol/L at 12 mo. Cu levels also declined from 9.76 +/- 2.05 mumol/L at 7 d to 3.46 +/- 0.79 mumol/L at 5 mo with little change thereafter. Zn and Cu were not affected by weaning. Mn concentrations declined from 67.4 +/- 23.7 nmol/L at 1 mo to approximately 36 nmol/L by 3 mo and then remained constant to 7 mo when mean levels started to rise. Gradual weaning was associated with large and irregular changes in Mn levels. Total daily outputs in milk averaged 26.0 mumol Zn, 3.9 mumol Cu, and 35 nmol Mn over the first 3 mo postpartum and 13.8 mumol Zn, 2.7 mumol Cu, and 29 nmol Mn over the second 3 mo.     

Mineral content of colostrum and mature milk of lactating Nigerian women as influenced by stage of lactation

380 milk samples (96 colostrum and 284 mature milk samples) collected from 240 lactating Nigerian women within the first 9 months of lactation were analyzed for zinc, copper, iron, calcium, and magnesium concentrations by atomic absorption spectrophotometry. Mean levels of zinc, copper, iron, calcium, and magnesium in colostrum were 5.83, 0.52, 0.55, 400, and 33 mcg/ml, respectively; the levels for the same minerals in mature milk collected in the 8th and 12th week of lactation were 3.08, 0.29, 0.38, 300, and 31 mcg/ml, respectively. While milk levels of all minerals decreased with increase in lactation age, zinc levels showed the fastest rate of decrease. Milk zinc levels at the 9th month were only 13% of that in colostrum. Similar percentages for copper, iron, calcium, and magnesium were 49, 60, 34, and 74%, respectively. Estimates of intake by solely breastfed infants during the first 6 months showed gross inadequacies when compared with Recommended Daily Allowances. Results suggest the need for early supplementation, especially as zinc deficiencies as well as a high incicdence of iron deficiency anemia has been reported in Nigerian infants.     

N-acetylneuraminic acid concentrations in human milk oligosaccharides and glycoproteins during lactation

Human milk contains a variety of N-acetylneuraminic acid (NANA)-containing oligosaccharides, but the expected range of intake of sialic acid in this form by infants fed human milk is unknown. Two quite different amounts have been reported: 120 mg/liter in pooled, mature human milk (1) and 1400 mg/liter in the milk of a single woman on the 1st day of lactation (2). The normal range of NANA intake in human milk glycoproteins likewise does not appear to have been analyzed previously. Data presented here indicate that both human milk oligosaccharide and glycoprotein NANA decline exponentially over the first 2 months of lactation, decreasing little thereafter. During the first 2 months of lactation, milk from women delivering at term cannot be distinguished from that of women delivering significantly before term (less than 32 wks gestation) with regard to oligosaccharide and glycoprotein NANA. The parallel decrease of sialic acid in these fractions suggests a relationship between sialydation of human milk oligosaccharides and glycoproteins. Human milk NANA concentrations are discussed with regard to reports that exogenous administration of NANA can increase cerebral and cerebellar concentrations of NANA in glycoproteins and gangliosides, and produce long term changes in behavior in rats.     

Polychlorinated biphenyls and organochlorine pesticides in milk and blood of Canadian women during lactation

Blood and breast milk samples of 16 women were analyzed for PCBs (polychlorinated biphenyls) and some organochlorine pesticides during eight intervals of a 98 day lactation period. Although a general downward trend in residue levels of blood and breast milk was evident, this trend was interrupted by sporadic increases. Most residues in breast milk showed an apparent increase during the first 30 days of lactation, which was not statistically significant. However, during lactation a statistically significant decrease was observed for the following residues, expressed on a milkfat basis: HCB (hexachlorobenzene), oxychlordane, transnonachlor (1-exo, 2-endo, 3-exo-4,5,6,7,8,8-nonachloro-3a,4,7,7a-tetrahydro-4,7-methanoindene), HCH (hexachlorocyclohexane),p,p-DDE andp,p-DDT. Average milk/blood ratios for PCBs, HCB, oxychlordane(1-exo,2-endo-4,5,6,7,8,8-oc-tachloro-2,3-exo-epoxy 2,3,3a,4,7,7a-hexa-hydro-4,7-methanoindene),p,p-DDE (2,2-bis-(p-chlorophenyl)- 1, 1-dichloroethylene), dieldrin (1,2,3,4, 10,10-hexachloro-exo-6,7-epoxy-1,4,4a,5,6,7,8,8a-octahydro- 1,4-endo- exo- 5,8-dimethanonaphthalene) and p,p-DDT (1,l-bis-(p-chlorophenyl)-2,2,2-trichloroethane) levels were 23, 20, 9, 19, 5 and 30 respectively. Milk/blood ratios for PCB andp,p-DDE levels remained relatively constant during lactation (coefficient of variation 20). Accumulation of residues in infant body fat were theoretically estimated     

Assessment of phytochemical content in human milk during different stages of lactation

ObjectiveThe present study reports the presence of several carotenoids and flavonoids in human milk samples.MethodsSamples were collected from 17 women who delivered healthy term babies (≥37 wk of gestation) at 1-, 4-, and 13-wk postpartum intervals.ResultsEpicatechin (63.7–828.5 nmol/L), epicatechin gallate (55.7–645.6 nmol/L), epigallocatechin gallate (215.1–2364.7 nmol/L), naringenin (64.1–722.0 nmol/L), kaempferol (7.8–71.4 nmol/L), hesperetin (74.8–1603.1 nmol/L), and quercetin (32.5–108.6 nmol/L) were present in human milk samples with high inter-/intraindividual variability. With the exception of kaempferol, the mean flavonoid content in human milk was not statistically different among lactation stages. In contrast, carotenoids α-carotene (59.0–23.2 nmol/L), β-carotene (164.3–88.0 nmol/L), α-cryptoxanthin (30.6–13.5 nmol/L), β-cryptoxanthin (57.4–24.8 nmol/L), zeaxanthin (46.3–21.4 nmol/L), lutein (121.2–56.4 nmol/L), and lycopene (119.9–49.5 nmol/L) significantly decreased from weeks 1 to 13 of lactation.ConclusionThe observed differences in the relative concentrations of the two phytochemical classes in human milk may be a result of several factors, including dietary exposure, stability in the milk matrix, efficiency of absorption/metabolism, and transfer from plasma to human milk. These data support the notion that flavonoids, as with carotenoids, are dietary phytochemicals present in human milk and potentially available to breast-fed infants.     

Determination of each neutral oligosaccharide in the milk of Japanese women during the course of lactation

Using reverse-phase HPLC after pyridylamination, we quantified the concentrations of major neutral oligosaccharides in the milk of sixteen Japanese women collected at 4, 10, 30 and 100 d postpartum. In colostrum and mature milk (30 d lactation), lacto-N-fucopentaose (LNFP) I was the most abundant oligosaccharide, followed by 2'-fucosyllactose (2'-FL) + lacto-N-difucotetraose (LNDFT), LNFP II + lacto-N-difucohexaose II (LNDFH II), and 3-fucosyllactose (3-FL). Together these accounted for 73 % of the total weight of neutral oligosaccharides in colostrum and mature milk. Changes in concentration occurred during the course of lactation. LNFP I and 2'-FL + LNDFT increased from 4 to 10 d postpartum, and then declined by 100 d. LNFP II + LNDFH II steadily increased during the first 30 d and then declined. In contrast, 3-FL increased steadily throughout the entire 100 d of study. Large differences were observed between our data and previously published data in Italian women, in terms of both the concentration and temporal changes of each oligosaccharide. These differences may be caused by different assay methodology, although racial differences cannot be ruled out.     

Relationships among human milk and plasma leptin concentrations and simple anthropometric measurements in lactating women

Leptin is a hormone that may be involved in energy balance as well as reproduction, and its concentration in the circulation is correlated to both total body fatness and milk leptin concentrations in lactating women. However, because many commonly-used indicators of total body fatness require highly technical and expensive pieces of equipment and may actually be inappropriate when studying lactating women, we were interested in investigating the relationships among more inexpensive and easily-obtained indicators of body composition, and plasma and milk leptin concentrations in lactating women. These indicators included triceps, subscapular and suprailiac skinfold thicknesses, body and limb circumferences, waist-to-hip ratio, upper arm and thigh muscle and fat areas. Results indicate that skim milk leptin concentrations tend to be high when these indicators are high. Further, plasma leptin concentrations are correlated strongly and positively with these simple indicators of adiposity. Plasma leptin concentrations in lactating women are described best by an equation that includes a combination of simple measures of subcutaneous fat and limb circumferences.     

Trace element compositional changes in human milk during the first four months of lactation

The aims of this paper were to evaluate changes in specific oligoelements in human milk during the first four months of lactation and to correlate such changes with total antioxidant status (TAS) and other parameters, such as the mother’s age, primipara versus multipara, and supplement intake. Milk samples were collected from 31 lactating women following 1, 4, 8, 12 and 16 weeks after birth. Trace levels of 13 elements were measured by inductively coupled plasma-mass spectrometry (ICP-MS). The results obtained for the oligoelements exhibited a decrease in concentration from 7 days to 4 months of breast-feeding, with exceptions. Correlations were found between TAS and Co, V, Rb and Tl. Between primipara and multipara, differences were found for Ni and Rb. Regarding the mother’s age, correlation was found for Rb and Ba (increased for mothers older than 30 years). Increased amounts of Rb, Mo and Tl at any lactation period appeared in women who took supplements.     

Energy metabolism, body composition, and milk production in healthy Swedish women during lactation

Variables of relevance to energy requirements during reproduction were studied in 23 healthy lactating Swedish women. Body composition and resting metabolic rate (RMR) were studied before pregnancy and three times postpartum. Energy intake was studied before pregnancy and, together with breast-milk production, 2 mo postpartum. The women gained 5.8 +/- 4.2 kg fat during pregnancy and their average fat content was unchanged during the first 2 mo of lactation whereas a slight loss (1.7 +/- 4.2 kg) occurred during the following 4 mo. RMR increased slightly during lactation in spite of a decrease in fat-free body weight 2 and 6 mo postpartum. Energy intake increased during lactation (280 +/- 440 kcal/d). The women produced 740 +/- 150 g breast milk/d containing 0.64 +/- 0.08 kcal/g. The results indicate that current estimates of energy needs during lactation may be too high.     

Delayed onset of lactation and risk of ending full breast-feeding early in rural Guatemala

Mothers of infants (n = 328) born between 1996 and 1999 in four Guatemalan communities were interviewed every 2 wk until 6 mo postpartum (pp) to collect prospective breast-feeding data and assess the association between delayed (>3 d pp) onset of lactation (OL) and the risk of ending full breast-feeding. Cox proportional hazards regression was used to examine the association between delayed OL and the hazard of ending full breast-feeding in the first 6 mo, adjusted for potential confounders and effect modifiers. A significant interaction with community was found (community-specific hazard ratios: HR(A) = 2.87, 95% CI = 1.25, 6.60; HR(B) = 3.43, 95% CI = 1.55, 7.59; HR(C) = 0.26, 95% CI = 0.06, 1.14; HR(D) = 1.11, 95% CI = 0.44, 2.77). Supplementation before OL (preonset supplementation) was associated with delayed OL [odds ratio (OR) = 4.87, 95% CI = 2.29, 10.36] and an increased risk of ending full breast-feeding (HR = 1.49, 95% CI = 1.05, 2.11). In the two communities in which mothers who experienced delayed OL had a significantly greater risk of ending full breast-feeding than did mothers experiencing normal OL, the association between delayed OL and full breast-feeding was mediated in part by preonset supplementation. Further analyses suggest that this was due to delayed OL leading to nonbreast milk feeds, rather than to introduction of supplements delaying OL. We conclude that some mothers who experience delayed OL are less likely to continue full breast-feeding in the first 6 mo and that further research should examine the contextual factors that modify this relationship.     

Transfer of cyproterone acetate to the milk of lactating women

Cyproterone acetate (CPA) was administered in a dose of 50 mg to 6 lactating women delivered by caesarean section. All women had to discontinue breast feeding the day before treatment. Prior to, and 3 and 9 hours after ingestion of the drug, plasma and milk specimens were taken. Total daily milk volume was recorded. Concentration of CPA in plasma and milk was determined by RIA.The plasma levels of CPA were in the range of 65–450 ng/ml at 3 h and 76–270 ng/ml after 9 hours. The respective concentrations in milk were 16–260 ng/ml (3 h) and 55–130 ng/ ml (9 h). The plasma/milk ratio of drug concentration varied between 1.1 and 9.3 (3 h) and 0.6 and 2.9 (9 h). The mean of all values amounted to 2.8 ± 2.3. Taking into account a daily milk production of 1050 ± 230 ml, 0.2 % of the dose administered (range: 0.06–0.41 % of dose) would have been transferred to the newborn. Use of the CPA-containing oral contraceptive DIANE^R (2 mg of CPA + 50 μ of ethinyl estradiol) by nursing women would therefore result in the transfer of 1 μ/kg to the child.