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Background: Human milk is the subject of many studies, but procedures for representative sample collection have not been established. Our improved methods for milk micronutrient analysis now enable systematic study of factors that affect its concentrations. Objective: We evaluated the effects of sample collection protocols, variations in circadian rhythms, subject variability, and acute maternal micronutrient supplementation on milk vitamin concentrations. Methods: In the BMQ (Breast-Milk-Quality) study, we recruited 18 healthy women (aged 18-26 y) in Dhaka, Bangladesh, at 2-4 mo of lactation for a 3-d supplementation study. On day 1, no supplements were given; on days 2 and 3, participants consumed ∼1 time and 2 times, respectively, the US-Canadian Recommended Dietary Allowances for vitamins at breakfast (0800-0859). Milk was collected during every feeding from the same breast over 24 h. Milk expressed in the first 2 min (aliquot I) was collected separately from the remainder (aliquot II); a third aliquot (aliquot III) was saved by combining aliquots I and II. Thiamin, riboflavin, niacin, and vitamins B-6, B-12, A, and E and fat were measured in each sample. Results: Significant but small differences (14-18%) between aliquots were found for all vitamins except for vitamins B-6 and B-12. Circadian variance was significant except for fat-adjusted vitamins A and E, with a higher contribution to total variance with supplementation. Between-subject variability accounted for most of the total variance. Afternoon and evening samples best reflected daily vitamin concentrations for all study days. Acute supplementation effects were found for thiamin, riboflavin, and vitamins B-6 and A at 2-4 h postdosing, with 0.1-6.17% passing into milk. Supplementation was reflected in fasting, 24-h postdose samples for riboflavin and vitamin B-6. Maximum amounts of dose-responding vitamins in 1 feeding ranged from 4.7% to 21.8% (day 2) and 8.2% to 35.0% (day 3) of Adequate Intake. Conclusions: In the milk of Bangladeshi mothers, differences in vitamin concentrations between aliquots within feedings and by circadian variance were significant but small. Afternoon and evening collection provided the most-representative samples. Supplementation acutely affects some breast-milk micronutrient concentrations. This trial was registered at clinicaltrials.gov as NCT02756026.

Background and Objectives: The World Health Organization recommends human immunodeficiency virus (HIV)-positive mothers in resource-poor regions heat-treat expressed breastmilk during periods of increased maternal-to-child transmission risk. Flash-heat, a "low tech" pasteurization method, inactivates HIV, but effects on milk protein bioactivity are unknown. The objectives were to measure flash-heat's effect on antimicrobial properties of lactoferrin, lysozyme, and whole milk and on the digestive resistance of lactoferrin and lysozyme., Methods: Flash-heated and unheated breastmilk aliquots from HIV-positive mothers in South Africa were "spiked" with Staphylococcus aureus and Escherichia coli and then cultured for 0, 3, and 6 hours. Lysozyme and lactoferrin activities were determined by lysis of Micrococcus luteus cells and inhibition of enteropathogenic E. coli, respectively, measured spectrophotometrically. Percentages of proteins surviving in vitro digestion, lactoferrin and lysozyme activity, and bacteriostatic activity of whole milk in heated versus unheated samples were compared., Results: There was no difference in rate of growth of E. coli or S. aureus in flash-heated versus unheated whole milk (p = 0.61 and p = 0.96, respectively). Mean (95% confidence interval) antibacterial activity of lactoferrin was diminished 11.1% (7.8%, 14.3%) and that of lysozyme by up to 56.6% (47.1%, 64.5%) by flash-heat. Digestion of lysozyme was unaffected (p = 0.12), but 25.4% less lactoferrin survived digestion (p < 0.0001)., Conclusions: In summary, flash-heat resulted in minimally decreased lactoferrin and moderately decreased lysozyme bioactivity, but bacteriostatic activity of whole milk against representative bacteria was unaffected. This suggests flash-heated breastmilk likely has a similar profile of resistance to bacterial contamination as that of unheated milk. Clinical significance of the decreased bioactivity should be tested in clinical trials.

Breastmilk is the only dietary source of zinc for exclusively breastfed young infants, and it remains a potentially important source of zinc for older infants and young children who continue breastfeeding beyond early infancy. Therefore, we examined available information on breastmilk zinc concentration and total milk consumption to develop estimates of the amount of zinc transferred in breastmilk to children of different ages. Breastmilk zinc concentration declines rapidly during the first few months postpartum and more slowly thereafter. Breastmilk supplies all of the theoretical zinc needs for at least the first several months of life, although the period during which breastmilk alone remains sufficient is uncertain. Breastmilk continues to provide more than half of children's estimated zinc requirements after the introduction of complementary foods, even into the second year of life. Public health programs to promote and support breastfeeding should be included among the strategies to ensure adequate zinc status of young children.

Background: Information is needed on the minimum energy density and feeding frequency of complementary foods that can provide adequate energy intakes (EIs) for healthy breastfed children., Objectives: The objectives of the study were to evaluate the effects of various energy densities and feeding frequencies of complementary foods on EI from these foods, breast milk consumption, and total EI from both sources., Design: During 9 separate, randomly ordered dietary periods lasting 3-6 d each, we measured intakes of food and breast milk by 18 healthy breastfed children 8-11 mo of age who, 3, 4, or 5 times/d, were fed porridge with a coded energy density of 0.5, 1.0, or 1.5 kcal/g. Food intake was measured by weighing the feeding bowl before and after meals, and breast milk intake was measured by test weighing., Results: The mean amounts of complementary foods consumed were inversely related to their energy density and positively related to the number of meals/d (P < 0.001 for both); EIs from foods were positively related to both factors. Breast milk intake decreased slightly but progressively, with greater energy density and feeding frequency of complementary foods; total EIs (kcal/d) increased in relation to both factors (P < 0.001 for both)., Conclusions: The energy density and feeding frequency of complementary foods affect infants' total daily EI and breast milk consumption. Recommendations can be developed for the appropriate combinations of these dietary factors that are compatible with adequate EI, although longer-term effects of complementary feeding practices on breast milk intake and breastfeeding duration need further community-based studies.

Background: Information is needed to design studies of the effects of complementary feeding regimens on children's intakes of complementary foods (CFs) and breast milk., Objective: We evaluated the effects of varied energy density of CFs on the time until stabilization of dietary intakes and on total daily energy intakes (EIs) and breast-milk intakes., Design: CFs with low [0.4 kcal/g (LD)] and high [1.5 kcal/g (HD)] energy density were fed 3 times/d to 10 children (aged 9-18 mo) during 2 randomly assigned sequences of three 8-d diet periods (HD-LD-HD or LD-HD-LD) along with ad libitum breastfeeding. CF and breast-milk intakes were measured., Results: Intakes of the HD diet and breast milk did not vary by day of period, but intake of the LD diet increased progressively. During days 5-7 of the last 2 diet periods in each sequence, more of the LD than of the HD diet was consumed (752 +/- 252 and 439 +/- 111 g/d, respectively; P < 0.001), but EIs from CFs were greater with the HD diet. Breast-milk consumption was slightly less (192 +/- 115 and 234 +/- 121 g/d, respectively; P = 0.03) but total daily EI was greater (774 +/- 175 and 441 +/- 85 kcal/d, respectively; P < 0.001) during the HD than during the LD diet period., Conclusions: New information on the effects of newly introduced diets on daily intakes of these diets and of breast milk can be used to design future studies. Total daily EIs were greater with the HD diet despite its negative effects on breast-milk intakes.

In developing countries, maternal infections during lactation are common. In this study, we evaluated the effect of acute maternal postpartum infection on the composition of colostrum and early milk with special emphasis on milk proteins and trace elements. The study was carried out in two maternity hospitals in Lima, Peru. Subjects were normally nourished women (body mass index (BMI) > 20.0) who intended to exclusively breastfeed their child and who had fever and clinical symptoms of infection within the first 48 h postpartum (n = 34). Non-ill women of similar characteristics were selected as controls (n = 23). Blood and milk samples were taken on days 1 and 14 postpartum. An acute phase response was confirmed by significantly increased serum levels of C-reactive protein in infected women. Serum zinc levels increased significantly from day 1 to day 14, but were not affected by infection. Serum copper levels were significantly higher in ill women than in non-ill women on day 1. All participating women were breastfeeding on day 14. Whey protein levels, the whey/casein ratio and total protein levels decreased significantly with time, but were not affected by infection. There were no differences in milk iron or copper levels with time or infection. Milk zinc levels decreased significantly with time, but were not affected by infection. Maternal infection during the early postpartum period does not appear to adversely affect the initiation of lactation or milk protein and trace element contents.

To investigate the potential effects of maternal infection during lactation on breast-milk quantity and composition, we examined low-income Peruvian women who had an acute febrile infection and were exclusively breast-feeding a child from 1 to 6 mo of age (n = 36). Women who were not ill (n = 38) served as controls; all women had body mass indexes (in kg/m2) > 19.5. Blood and milk samples were collected on days 1, 7, and 14 after identification of the episode of illness. C-reactive protein in maternal serum was significantly elevated by infection, whereas two other acute-phase reactants, ceruloplasmin and alpha 2-macroglobulin, showed no change. Serum zinc concentrations were significantly lower in ill women than in women who were not ill, whereas serum copper concentrations were elevated initially in ill women. Serum iron concentrations increased significantly with time, but there was no significant difference between groups. Milk intake, as assessed by 12-h test-weighing, was not affected by the infection. Concentrations of milk total protein, casein, and whey proteins were similar in the two groups and there was no significant effect of illness on milk trace element concentrations. Thus, acute maternal infections during established lactation did not affect milk volume, milk protein, or trace element concentrations, despite expected changes in serum protein and trace element concentrations.

Intake and growth were compared between matched cohorts of infants either breast-fed (BF) or formula-fed (FF) until > or = 12 mo of age. Total energy intake at 3, 6, 9, and 12 mo averaged 0.36, 0.34, 0.35, and 0.38 MJ.kg-1.d-1 (85.9, 80.1, 83.6, and 89.8 kcal.kg-1.d-1) among BF infants vs 0.41, 0.40, 0.39, and 0.41 MJ.kg-1.d-1 (98.7, 94.7, 93.6, and 98.0 kcal.kg-1.d-1) among FF infants, respectively. Protein intake was 66-70% higher in the FF than in the BF group during the first 6 mo. Differences in energy and protein intakes were significant at 3, 6, and 9 mo. Gains in weight and lean body mass were lower in BF than in FF infants from 3 to 9 mo. BF infants gained more weight and lean body mass per gram protein intake but not per megajoule intake. Although growth differences between groups were related to differences in intake, there is no evidence of any functional advantage to the more rapid growth of FF infants.

To determine the effect of dietary viscosity on energy consumption by young children, 56 Peruvian children 9-20 mo of age with acute diarrhea were randomly assigned to either a liquid or semisolid diet, with or without added amylase to reduce viscosity. Intakes of the study diet, breast milk, and other foods were measured for 2 consecutive d during and again after illness. Total 24-h energy intake (chi +/- SD) during diarrhea, 349.4 +/- 121.8 kJ/kg (83.6 +/- 29.1 kcal/kg) was 18% less than intake after recovery, 428.9 +/- 141.0 kJ/kg (102.6 +/- 33.7), P < 0.001. In the ANOVA breast-fed children consumed significantly less total energy (P = 0.008) and energy from the study diet (P = 0.02) than non-breast-fed children. Breast milk intake did not change with illness. There was no significant relationship between viscosity of the study diet and either total energy intake or intake of energy from the study diet. Energy intake by these children was primarily determined by health status and breast-feeding practice, not by dietary viscosity.

Anthropometric indexes from 1 to 24 mo were compared between matched cohorts of infants either breast-fed (BF, n = 46) or formula-fed (FF, n = 41) until > or = 12 mo. Neither group received solid foods before 4 mo. Weight-for-length was significantly greater among FF infants from 7 to 24 mo. In both groups, skinfold thickness (triceps, biceps, subscapular, flank, and quadriceps) and estimated percent body fat (%FAT) increased rapidly during the first 6-8 mo and declined thereafter. At all sites except biceps, FF infants had larger skinfold thicknesses in later infancy (particularly 9-15 mo) than did BF infants; %FAT was significantly higher from 5 to 24 mo. Lower energy intake among BF infants explained the difference between groups. Maternal and infant fatness were positively correlated at 12-24 mo. Breast-milk lipid and energy concentration were unrelated to infant fatness. These results indicate that infants BF for > or = 12 mo are leaner than their FF counterparts.