Daily selenium intake by breast-fed infants and the selenium concentration in the milk of lactating women in western Poland.

BACKGROUND: Human milk is the only natural source of food for infants during the first several months of life. The milk should contain all trace elements in adequate amounts, including selenium (Se). Se is of particular interest because the daily requirement for this element in infants is higher due to their rapid growth. The aim of our study was to determine the Se concentration in human milk and to calculate the daily Se intake by breast-fed infants in western Poland. MATERIAL AND METHODS: The Se concentration was assayed in mature human milk (14 to 58 days after parturition) collected from 352 lactating women living in 7 voivodeships in western Poland. The concentration of Se was measured by the fluorometric method with 2,3-diaminonaphthalene as a complexing reagent. The values were expressed as ng/ml. RESULTS: No significant differences were observed in terms of Se concentration among the milk samples collected from the different voivodeships. However, the highest values were obtained in the northern part of the region. The mean Se concentration was 10.51 +/- 2.76 ng/ml (range: 10.41-10.65 ng/ml). The calculated mean daily Se intake by breast-fed infants was 7.71 microg/day (range: 3.67-17.17 microg/day). CONCLUSIONS: The Se concentration in human milk in the region studied here is uniform, but the daily Se intake of breast-fed infants in the western part of Poland is lower than the recommended daily requirement. The reason for this situation would appear to be low Se content in the soil, and consequently in the foodstuffs from this region.

Selenium concentration in the milk of breast-feeding mothers and its geographic distribution.

A total of 905 human milk samples collected in all provinces of Poland, between 12 and 75 days of lactation, were analyzed for selenium concentration. The distribution of Se levels in milk between the provinces was narrow and varied from 8.81 to 11.58 ng/mL, with the mean value (+/- SD) of 10.24 +/- 2.82 ng/mL. The regions with lower levels of Se were in the central and eastern part of Poland; the areas with higher values were in the northern, western, and southern parts of Poland. No significant correlations were found between Se levels in milk and the age of lactating mothers or between Se levels and the postpartum period. The calculated daily Se intakes by breast-fed infants varied from 6.46 to 8.50 microg/day, with the mean value of 7.52 microg/day. This amount does not meet the recommended dietary allowances for infants between 0 and 6 months of age. Based on Se levels in human milk, we present a selenium map of Poland.

Decreased selenium concentration in maternal and cord blood in preterm compared with term delivery.

The Se concentration in maternal and cord whole blood and plasma was determined spectrofluorimetrically in: (1) 42 women at term and (2) 46 at preterm parturients, and in the placenta. The glutathione peroxidase (GSH-Px) activity was measured in red cells and plasma in maternal and cord blood of both groups. The Se concentrations and GSH-Px activities of the above-mentioned groups were compared with those of non-pregnant women. Whole blood and plasma Se concentration of parturients at term did not differ significantly from those of non-pregnant women (72.3 versus 80.3 ng ml-1 whole blood and 48.7 versus 56.2 ng ml-1 plasma). In preterm parturients, however, Se concentrations were significantly lower (61.1 ng ml-1 whole blood and 39.2 ng ml-1 plasma) when compared with term parturients. The Se levels in cord blood and plasma were similar to their mothers' Se concentrations. No difference was observed in placenta Se levels (130 ng g-1 wet weight in both groups). The same was true for glutathione (GSH): the concentration in maternal and cord blood of term and preterm parturients did not differ and varied from 2.43 to 2.50 mmol l-1 red cells. Red cell GSH-Px activities were similar in maternal and cord blood of both term and preterm groups and ranged from 14.3 to 15.7 U g-1 Hb. The plasma enzyme activity in the maternal blood of preterm parturients was significantly (p < 0.05) lower than that of mothers at term delivery. The GSH-Px activity in the plasma of cord blood was significantly (p < 0.001) lower in the preterm than in the term group. It is suggested that low Se levels in the blood of women at preterm delivery, as shown here, may be one of the causes of retinopathy and respiratory distress syndrome in preterm infants.