Mineral compositions in breast milk of healthy Chinese lactating women in urban areas and its associated factors / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Optimal mineral intakes are important for infant growth and development. However, data on mineral compositions of breast milk in Chinese women are scarce, and most were acquired before 1990. The objectives of this study were three-fold: (1) to investigate the mineral compositions of Chinese healthy mothers' breast milk in different lactation stages; (2) to explore correlations among mineral concentrations in breast milk; and (3) to explore the associated factors affecting mineral compositions in breast milk.</p><p><b>METHODS</b>The inductively coupled plasma mass spectrometry (ICP-MS) was used to analyze mineral concentrations in breast-milk of 444 healthy lactating women from three cities in China. A questionnaire was used to survey socio-demographic characteristics and pregnancy history. Food intakes by lactating women were measured using both food frequency questionnaire and one cycle of 24-hour dietary recall.</p><p><b>RESULTS</b>Mineral compositions of breast milk varied in different regions. Concentrations of most minerals were higher in the first one or two months of lactation, and then decreased with time, except for magnesium and iron. Inter-mineral correlations existed among several minerals. The calcium-to-phosphorus ratio was above 2:1 in each lactation stage. Women with caesarean section had higher concentration of iodine in the transitional milk (349.9 µg/kg) compared to women with natural delivery (237.5 µg/kg, P < 0.001). Dietary mineral intakes, supplements, food intake frequencies in the recent 6 months, maternal age and maternal BMI did not show significant correlations with concentrations of milk minerals (all P > 0.05).</p><p><b>CONCLUSIONS</b>Milk minerals decreased with time, and changed most rapidly in the first one or two months of lactation. Caesarean section might affect the iodine level in transitional milk.</p>

Breast milk macronutrient composition and the associated factors in urban Chinese mothers / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Infancy is a critical period of growth and physiological development, in which breast milk is the best source of nutrients. Compared to western countries, research on breast milk of Chinese population are limited. Thus, it is necessary to measure breast milk energy and macronutrient concentrations of healthy urban Chinese mothers at different lactation stages, to expand the database of milk composition of Chinese population, and to examine whether dietary or other maternal factors can affect the levels of macronutrients in breast milk.</p><p><b>METHODS</b>Breast milk of full expression of one side breast from 436 urban Chinese lactating mothers at 5-11 days, 12-30 days, 31-60 days, 61-120 days, and 121-240 days postpartum was obtained at 9:00 a.m. to 11:00 a.m. Total energy, lactose, protein, and fat contents were measured. 24-hour dietary recall was surveyed, and maternal nutrient intakes were analyzed.</p><p><b>RESULTS</b>Milk composition changed over the course of lactation and large individual variations were documented. The concentrations were 61.3 kcal/dl for total energy, 7.1 g/dl for lactose, 0.9 g/dl for protein, and 3.4 g/dl for fat in mature milk. Stage of lactation was a strong factor affecting milk composition. Minimal evidence was found for associations between maternal current dietary intake and milk macronutrient concentration, consistently with prior research. Maternal body mass index (BMI) was positively associated with milk fat content, to a greater extent than did dietary intake. All other maternal characteristics were not significant for milk composition.</p><p><b>CONCLUSION</b>These findings suggest that milk composition is generally weakly associated with maternal factors except for stage of lactation, and is likely to be more susceptible to long-term maternal nutritional status than short-term dietary fluctuation.</p>