Evidence from the nutritional literature suggests that mineral intakes in Western populations are below those recommended for optimal health. This likely results from the poor quality diets eaten in Westernised countries. Selenium is one mineral that has been consistently identified as being deficient in developed nations. This is of particular concern because chronic low intakes of selenium are increasingly being linked to the development of cancer. Certain countries such as New Zealand and Finland have been identified as having low selenium soils and so crops grown on these soils may be devoid of meaningful levels of selenium. Frequent consumptions of selenium deficient crops may contribute to low selenium intakes and a large body of research has been performed to assess the selenium intakes of populations from selenium deficient areas and how they respond to supplements. In particular, the requirement for minerals increases during pregnancy and so concerns about maternal selenium intakes is of particular interest.
Researchers have investigated the effects of selenium supplementation on the selenium status of lactating mothers and their infants in Finland. Mothers were fed either 100 μg per day of inorganic selenium in the form of selenite or 100 μg per day of organically bound selenium yeast1. Both selenium supplements were effective at raising serum levels of selenium, suggesting that the baseline intake of the mothers was below the optimum intake. However, those subject not receiving a selenium supplement had no change in their serum levels of selenium. As has been shown elsewhere, the organically bound selenium increased plasma selenium concentrations more effectively that than the inorganically bound selenite supplements. Selenium concentrations in the serum of the infants also increased following supplementation of the mothers, suggesting that the selenium had been transferred to the infants through the milk. Small increases in selenium in the milk of the mothers taking selenium supplements compared to the control supported this viewpoint.
Selenium supplementation in breastfeeding mothers therefore appears to be beneficial at raising the serum selenium levels of both infants and mothers. The subjects in this study were Finnish, and Finland is known to possess low selenium soils, which may explain the initial low (53 to 59 μg/L) serum levels of the subjects. Serum levels following 6 months rose to around 140 and 110 μg/L in the organic and inorganic selenium groups, respectively. However, while the serum of the mothers had plateaued at 6 month, the serum of the infants continued to rise. In the 6 month study the serum selenium concentrations of the infants rose from around ~40 μg/L to ~85 μg/L and from ~45 μg/L to ~65 μg/L in the organic and inorganic supplement groups, respectively. Correlation statistics showed that there was a positive association between the maternal serum selenium concentrations and those of the infants. Optimising maternal selenium intakes may therefore provide optimal infant selenium status which may confer subsequent disease protection.
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